WorldWideScience

Sample records for bistable semiconductor lasers

  1. Excitonic bistabilities, instabilities and chaos in laser-pumped semiconductor

    International Nuclear Information System (INIS)

    Nguyen Ba An; Nguyen Trung Dan; Hoang Xuan Nguyen

    1992-07-01

    The Hurwitz criteria are used for a stability analysis of the steady state excitonic optical bistability curves in a semiconductor pumped by an external laser resonant with the exciton level. Besides the middle branch of the bistability curves which is unstable in the sense of the linear stability theory, we have found other domains of instability in the upper and lower branches of the steady state curves. Numerical results show that a possible route to chaos in the photon-exciton system is period-doubling self-oscillation process. The influence of the presence of free carriers that coexist with the excitons is also discussed. (author). 16 refs, 6 figs

  2. Bistability and self-oscillations effects in a polariton-laser semiconductor microcavity

    International Nuclear Information System (INIS)

    Cotta, E A; Matinaga, F M

    2007-01-01

    We report an experimental observation of polaritonic optical bistability of the laser emission in a planar semiconductor microcavity with a 100 0 A GaAs single quantum well in the strong-coupling regime. The bistability curves show crossings that indicate a competition between a Kerr-like effect induced by the polariton population and thermal effects. Associated with the bistability, laser-like emission occurs at the bare cavity mode

  3. Bistable amphoteric centers in semiconductors

    International Nuclear Information System (INIS)

    Nikitina, A. G.; Zuev, V. V.

    2008-01-01

    It is shown that, at thermodynamic equilibrium, the release of charge carriers from the localized states of bistable amphoteric centers into quasi-free states depends on the degree of compensation. This brings about different functional dependences of the concentration of free charge carriers on temperature. It is found that, in uncompensated semiconductors, the concentration of free charge carriers follows the same dependence in the case of bistable amphoteric centers and bistable amphoteric U - centers, although the distributions of charge carriers over the charge states and configurations are different for these types of centers. The results can be used for interpreting various experimental data insufficiently explained in the context of the traditional approach

  4. Switching waves dynamics in optical bistable cavity-free system at femtosecond laser pulse propagation in semiconductor under light diffraction

    Science.gov (United States)

    Trofimov, Vyacheslav A.; Egorenkov, Vladimir A.; Loginova, Maria M.

    2018-02-01

    We consider a propagation of laser pulse in a semiconductor under the conditions of an occurrence of optical bistability, which appears due to a nonlinear absorption of the semiconductor. As a result, the domains of high concentration of free charged particles (electrons and ionized donors) occur if an intensity of the incident optical pulse is greater than certain intensity. As it is well-known, that an optical beam must undergo a diffraction on (or reflection from) the domains boundaries. Usually, the beam diffraction along a coordinate of the optical pulse propagation does not take into account by using the slowly varying envelope approximation for the laser pulse interaction with optical bistable element. Therefore, a reflection of the beam from the domains with abrupt boundary does not take into account under computer simulation of the laser pulse propagation. However, the optical beams, reflected from nonhomogeneities caused by the domains of high concentration of free-charged particles, can essentially influence on a formation of switching waves in a semiconductor. We illustrate this statement by computer simulation results provided on the base of nonlinear Schrödinger equation and a set of PDEs, which describe an evolution of the semiconductor characteristics (concentrations of free-charged particles and potential of an electric field strength), and taking into account the longitudinal and transverse diffraction effects.

  5. Bistability and low-frequency fluctuations in semiconductor lasers with optical feedback: a theoretical analysis

    DEFF Research Database (Denmark)

    Mørk, Jesper; Tromborg, Bjarne; Christiansen, Peter Leth

    1988-01-01

    Near-threshold operation of a semiconductor laser exposed to moderate optical feedback may lead to low-frequency fluctuations. In the same region, a kink is observed in the light-current characteristic. Here it is demonstrated that these nonlinear phenomena are predicted by a noise driven multimode...

  6. Excitonic optical bistability in n-type doped semiconductors

    International Nuclear Information System (INIS)

    Nguyen Ba An; Le Thi Cat Tuong

    1991-07-01

    A resonant monochromatic pump laser generates coherent excitons in an n-type doped semiconductor. Both exciton-exciton and exciton-donor interactions come into play. The former interaction can give rise to the appearance of optical bistability which is heavily influenced by the latter one. When optical bistability occurs at a fixed laser frequency both its holding intensity and hysteresis loop size are shown to decrease with increasing donor concentration. Two possibilities are suggested for experimentally determining one of the two parameters of the system - the exciton-donor coupling constant and the donor concentration, if the other parameter is known beforehand. (author). 36 refs, 2 figs

  7. Bistability in a laser with injected signal

    International Nuclear Information System (INIS)

    Dorobantu, I.A.; Vlad, V.I.; Ursu, I.

    1987-04-01

    A unified description of bistability is given in free running lasers, optical bistable devices, ring lasers and lasers with an injected signal (LIS). A general review of laser instabilities is also presented in the frame of the theory of elementary catastrophes, emphasizing the apparence of higher order catastrophes in the case of a LIS suggesting thus a possibility to devise from first principles the whole hierarchy of laser instabilities. Experimental results on the bistability in the polarisation of LIS are also discussed. (authors)

  8. Bistable laser device with multiple coupled active vertical-cavity resonators

    Science.gov (United States)

    Fischer, Arthur J.; Choquette, Kent D.; Chow, Weng W.

    2003-08-19

    A new class of bistable coupled-resonator vertical-cavity semiconductor laser devices has been developed. These bistable laser devices can be switched, either electrically or optically, between lasing and non-lasing states. A switching signal with a power of a fraction of a milliwatt can change the laser output of such a device by a factor of a hundred, thereby enabling a range of optical switching and data encoding applications.

  9. Semiconductor Laser Measurements Laboratory

    Data.gov (United States)

    Federal Laboratory Consortium — The Semiconductor Laser Measurements Laboratory is equipped to investigate and characterize the lasing properties of semiconductor diode lasers. Lasing features such...

  10. Magnetic-field induced bistability in a quasi-one-dimensional semiconductor microcavity

    International Nuclear Information System (INIS)

    Zhang, Chuanyi; Zhang, Weifeng

    2015-01-01

    We theoretically study the magnetic-field induced bistability in a quasi-one-dimensional semiconductor microcavity. A critical magnetic field is obtained, and the bistability appears if a magnetic field is greater than the critical value. For a positive energy detuning of the pump from the bare exciton polaritons, one bistability loop first emerges, then it divides into two loops, and finally one of them vanishes with the increasing magnetic field. This phenomenon originates from the magnetic-field modulated interactions for opposite spins. In the variational process, there are two important effects: one is a logic gate with a small variation of the excitation laser, and the other is a spin texture like skyrmion and this texture is periodic if the energy detuning varies periodically in real space, which is useful for designing the spin-dependent optoelectronic devices. - Highlights: • We study the bistability induced by a magnetic field in a microcavity. • One bistability loop can divide into two, and then the two loops return to one. • A spin texture like skyrmion and logic gate arise in the variation of bistability loop

  11. Semiconductor laser shearing interferometer

    International Nuclear Information System (INIS)

    Ming Hai; Li Ming; Chen Nong; Xie Jiaping

    1988-03-01

    The application of semiconductor laser on grating shearing interferometry is studied experimentally in the present paper. The method measuring the coherence of semiconductor laser beam by ion etching double frequency grating is proposed. The experimental result of lens aberration with semiconductor laser shearing interferometer is given. Talbot shearing interferometry of semiconductor laser is also described. (author). 2 refs, 9 figs

  12. Internal optical bistability of quasi-two-dimensional semiconductor nanoheterostructures

    Science.gov (United States)

    Derevyanchuk, Oleksandr V.; Kramar, Natalia K.; Kramar, Valeriy M.

    2018-01-01

    We represent the results of numerical computations of the frequency and temperature domains of possible realization of internal optical bistability in flat quasi-two-dimensional semiconductor nanoheterostructures with a single quantum well (i.e., nanofilms). Particular computations have been made for a nanofilm of layered semiconductor PbI2 embedded in dielectric medium, i.e. ethylene-methacrylic acid (E-MAA) copolymer. It is shown that an increase in the nanofilm's thickness leads to a long-wave shift of the frequency range of the manifestation the phenomenon of bistability, to increase the size of the hysteresis loop, as well as to the expansion of the temperature interval at which the realization of this phenomenon is possible.

  13. Bistable polarization switching in a continuous wave ruby laser

    Science.gov (United States)

    Lawandy, N. M.; Afzal, R. Sohrab

    1988-01-01

    Bistability in the output power, polarization state, and mode volume of an argon-ion laser pumped single mode ruby laser at 6943 A has been observed. The laser operates in a radially confined mode which exhibits hysteresis and bistability only when the pump polarization is parallel to the c-axis.

  14. Bistable behaviour of biexciton population in a dense exciton-biexciton system in semiconductors

    International Nuclear Information System (INIS)

    Nguyen Ba An.

    1986-05-01

    The steady state bistable behaviour of biexciton population in a dense exciton-biexciton semiconductor is considered. The intrinsic optical feedback is provided by the recombination mechanism. The exciton-biexciton and biexciton-biexciton interactions play the role of non-linearity responsible for biexciton bistability to occur. The conditions leading to the effect of bistability are obtained and two-parameter phase transition diagrams are drawn for both intensity and frequency bistable phenomena. (author)

  15. Physics of semiconductor lasers

    CERN Document Server

    Mroziewicz, B; Nakwaski, W

    2013-01-01

    Written for readers who have some background in solid state physics but do not necessarily possess any knowledge of semiconductor lasers, this book provides a comprehensive and concise account of fundamental semiconductor laser physics, technology and properties. The principles of operation of these lasers are therefore discussed in detail with the interrelations between their design and optical, electrical and thermal properties. The relative merits of a large number of laser structures and their parameters are described to acquaint the reader with the various aspects of the semiconductor l

  16. Compact semiconductor lasers

    CERN Document Server

    Yu, Siyuan; Lourtioz, Jean-Michel

    2014-01-01

    This book brings together in a single volume a unique contribution by the top experts around the world in the field of compact semiconductor lasers to provide a comprehensive description and analysis of the current status as well as future directions in the field of micro- and nano-scale semiconductor lasers. It is organized according to the various forms of micro- or nano-laser cavity configurations with each chapter discussing key technical issues, including semiconductor carrier recombination processes and optical gain dynamics, photonic confinement behavior and output coupling mechanisms, carrier transport considerations relevant to the injection process, and emission mode control. Required reading for those working in and researching the area of semiconductors lasers and micro-electronics.

  17. Single frequency semiconductor lasers

    CERN Document Server

    Fang, Zujie; Chen, Gaoting; Qu, Ronghui

    2017-01-01

    This book systematically introduces the single frequency semiconductor laser, which is widely used in many vital advanced technologies, such as the laser cooling of atoms and atomic clock, high-precision measurements and spectroscopy, coherent optical communications, and advanced optical sensors. It presents both the fundamentals and characteristics of semiconductor lasers, including basic F-P structure and monolithic integrated structures; interprets laser noises and their measurements; and explains mechanisms and technologies relating to the main aspects of single frequency lasers, including external cavity lasers, frequency stabilization technologies, frequency sweeping, optical phase locked loops, and so on. It paints a clear, physical picture of related technologies and reviews new developments in the field as well. It will be a useful reference to graduate students, researchers, and engineers in the field.

  18. Fundamentals of semiconductor lasers

    CERN Document Server

    Numai, Takahiro

    2015-01-01

    This book explains physics under the operating principles of semiconductor lasers in detail based on the experience of the author, dealing with the first manufacturing of phase-shifted DFB-LDs and recent research on transverse modes.   The book also bridges a wide gap between journal papers and textbooks, requiring only an undergraduate-level knowledge of electromagnetism and quantum mechanics, and helps readers to understand journal papers where definitions of some technical terms vary, depending on the paper. Two definitions of the photon density in the rate equations and two definitions of the phase-shift in the phase-shifted DFB-LD are explained, and differences in the calculated results are indicated, depending on the definitions.    Readers can understand the physics of semiconductor lasers and analytical tools for Fabry-Perot LDs, DFB-LDs, and VCSELs and will be stimulated to develop semiconductor lasers themselves.

  19. Temperature controller of semiconductor laser

    Czech Academy of Sciences Publication Activity Database

    Matoušek, Vít; Číp, Ondřej

    2003-01-01

    Roč. 73, č. 3 (2003), s. 10 - 12 ISSN 0928-5008 Institutional research plan: CEZ:AV0Z2065902 Keywords : temperature controller * semiconductor laser * laser diode Subject RIV: BH - Optics, Masers, Lasers

  20. High-power subnanosecond operation of a bistable optically controlled semiconductor switch (BOSS)

    International Nuclear Information System (INIS)

    Stoudt, D.C.; Richardson, M.A.; Demske, D.L.; Roush, R.A.; Eure, K.W.

    1994-01-01

    Recent high-power, subnanosecond-switching results of the Bistable Optically controlled Semiconductor Switch (BOSS) are presented. The process of persistent photoconductivity followed by photo-quenching have been demonstrated at megawatt power levels in copper-compensated, silicon-doped, semi-insulating gallium arsenide. These processes allow a switch to be developed that can be closed by the application of one laser pulse and opened by the application of a second laser pulse with a wavelength equal to twice that of the first laser. Switch closure is primarily achieved by elevating electrons from a deep copper center which has been diffused into the material. The opening phase is a two-step process which relies initially on the absorption of the 2-μm laser causing electrons to be elevated from the valance band back into the copper center, and finally on the recombination of electrons in the conduction band with boles in the valance band. The second step requires a sufficient concentration of recombination centers (RC) in the material for opening to occur in the subnanosecond regime. These RC's are generated in the bulk GaAs material by fast-neutron irradiation (∼ 1 MeV) at a fluence of about 3 x 10 15 cm -2 . High-power switching results which demonstrate that the BOSS switch can be opened in the subnanosecond regime are presented for the first time. Neutron-irradiated BOSS devices have been opened against a rising electric field of about 20 kV/cm (10 kV) in a time less than one nanosecond. Kilovolt electrical pulses have been generated with a FWHM of roughly 250 picoseconds

  1. Single filament semiconductor laser

    International Nuclear Information System (INIS)

    Botez, D.

    1980-01-01

    A semiconductor laser comprising: a body of semiconductor material including a substrate having a surface and a pair of spaced, substantially parallel dove-tailed shaped grooves in said surface, said body having a pair of end surfaces between which said grooves extend, said end surfaces being reflective to light with at least one of said end surfaces being partially transparent to light a first epitaxial layer over said surface of the substrate and the surfaces of the grooves, said first epitaxial layer having a flat surface portion over the portion of the substrate surface between the grooves, a thin second epitaxial layer over said first epitaxial layer, a third epitaxial layer over said second epitaxial layer, said first and third epitaxial layers being of opposite conductivity types and the second epitaxial layer being the active recombination region of the laser with the light being generated therein in the vicinity of the portion which is over the flat surface portion of the first epitaxial layer, and a pair of contacts on said body with one contact being over said third epitaxial body and the other being on said substrate

  2. Oscillatory bistability of real-space transfer in semiconductor heterostructures

    Science.gov (United States)

    Do˙ttling, R.; Scho˙ll, E.

    1992-01-01

    Charge transport parallel to the layers of a modulation-doped GaAs/AlxGa1-xAs heterostructure is studied theoretically. The heating of electrons by the applied electric field leads to real-space transfer of electrons from the GaAs into the adjacent AlxGa1-xAs layer. For sufficiently large dc bias, spontaneous periodic 100-GHz current oscillations, and bistability and hysteretic switching transitions between oscillatory and stationary states are predicted. We present a detailed investigation of complex bifurcation scenarios as a function of the bias voltage U0 and the load resistance RL. For large RL subcritical Hopf bifurcations and global bifurcations of limit cycles are displayed.

  3. A semiconductor laser device

    Energy Technology Data Exchange (ETDEWEB)

    Takaro, K.; Naoki, T.; Satosi, K.; Yasutosi, K.

    1984-03-17

    A device is proposed which makes it possible to obtain single vertical mode emission in the absence of noise. Noise suppression is achieved by a method which determines the relationship between the donor densities in the second and third layers of an n type semiconductor laser, and the total output optical emission of layers with respect to the emission from the entire laser. The device consists of a photoresist film with a window applied to a 100 GaAs n type conductivity substrate using a standard method. Chemical etching through this window in the substrate is used to generate a slot approximately 1 micrometer in size. After the photoresist film is removed, the following layers are deposited from the liquid phase onto the substrate in the sequence indicated: a telurium doped protective layer of n type AlxGa(1-x) As; 2) an undoped active p type AlyGa(1-6) As layer and a tellurium doped upper protective n type conductivity GaAs layer.

  4. Semiconductor lasers stability, instability and chaos

    CERN Document Server

    Ohtsubo, Junji

    2017-01-01

    This book describes the fascinating recent advances made concerning the chaos, stability and instability of semiconductor lasers, and discusses their applications and future prospects in detail. It emphasizes the dynamics in semiconductor lasers by optical and electronic feedback, optical injection, and injection current modulation. Applications of semiconductor laser chaos, control and noise, and semiconductor lasers are also demonstrated. Semiconductor lasers with new structures, such as vertical-cavity surface-emitting lasers and broad-area semiconductor lasers, are intriguing and promising devices. Current topics include fast physical number generation using chaotic semiconductor lasers for secure communication, development of chaos, quantum-dot semiconductor lasers and quantum-cascade semiconductor lasers, and vertical-cavity surface-emitting lasers. This fourth edition has been significantly expanded to reflect the latest developments. The fundamental theory of laser chaos and the chaotic dynamics in se...

  5. Semiconductor lasers and herterojunction leds

    CERN Document Server

    Kressel, Henry

    2012-01-01

    Semiconductor Lasers and Heterojunction LEDs presents an introduction to the subject of semiconductor lasers and heterojunction LEDs. The book reviews relevant basic solid-state and electromagnetic principles; the relevant concepts in solid state physics; and the p-n junctions and heterojunctions. The text also describes stimulated emission and gain; the relevant concepts in electromagnetic field theory; and the modes in laser structures. The relation between electrical and optical properties of laser diodes; epitaxial technology; binary III-V compounds; and diode fabrication are also consider

  6. Towards filament free semiconductor lasers

    DEFF Research Database (Denmark)

    McInerney, John; O'Brien, Peter; Skovgaard, Peter M. W.

    2000-01-01

    We outline physical models and simulations for suppression of self-focusing and filamentation in large aperture semiconductor lasers. The principal technical objective is to generate multi-watt CW or quasi-CW outputs with nearly diffraction limited beams, suitable for long distance free space...... propagation structures in lasers and amplifiers which suppress lateral reflections....

  7. Waveguide based external cavity semiconductor lasers

    NARCIS (Netherlands)

    Oldenbeuving, Ruud; Klein, E.J.; Offerhaus, Herman L.; Lee, Christopher James; Verhaegen, M.; Boller, Klaus J.

    2012-01-01

    We report on progress of the project waveguide based external cavity semiconductor laser (WECSL) arrays. Here we present the latest results on our efforts to mode lock an array of tunable, external cavity semiconductor lasers.

  8. Optical bistability in the oscillation of an inhomogeneously broadened quasi-three-level laser

    International Nuclear Information System (INIS)

    Liu, Junhai; Tian, Xueping

    2013-01-01

    A theoretical modeling analysis is presented to study the optical bistability exhibited in the oscillation of an inhomogeneously broadened quasi-three-level laser. All the major characteristics of optical bistability depend on two normalized parameters, f and x a , which are defined by f = I sat,a /I sat,m and x a = 2α a0 p a /δ and are related to measurable properties of the laser medium. In comparison with the case of a homogeneously broadened laser, the essential condition for the occurrence of such bistability, f a /(x a + 1), turns out to be the same, whereas the intensities at the up- and down-thresholds are substantially increased and the bistability range is reduced. (paper)

  9. Laser semiconductor diode integrated with frequency doubler

    International Nuclear Information System (INIS)

    Tighineanu, I.; Dorogan, V.; Suruceanu, G.

    2003-01-01

    The invention relates to the technology of optoelectronic semiconductor devices and may be used in the production of laser semiconductor diodes integrated with optical nonlinear elements. The laser semiconductor diode integrated with frequency doubler includes a semiconductor substrate, a laser structure with waveguide. metal contacts in the waveguide of the laser structure it is formed a nanostructured field so that the nanostructure provides for the fulfillment of the phase synchronism conditions

  10. Advances in semiconductor lasers

    CERN Document Server

    Coleman, James J; Jagadish, Chennupati

    2012-01-01

    Semiconductors and Semimetals has distinguished itself through the careful selection of well-known authors, editors, and contributors. Originally widely known as the ""Willardson and Beer"" Series, it has succeeded in publishing numerous landmark volumes and chapters. The series publishes timely, highly relevant volumes intended for long-term impact and reflecting the truly interdisciplinary nature of the field. The volumes in Semiconductors and Semimetals have been and will continue to be of great interest to physicists, chemists, materials scientists, and device engineers in academia, scien

  11. Semiconductor processing with excimer lasers

    International Nuclear Information System (INIS)

    Young, R.T.; Narayan, J.; Christie, W.H.; van der Leeden, G.A.; Rothe, D.E.; Cheng, L.J.

    1983-01-01

    The advantages of pulsed excimer lasers for semiconductor processing are reviewed. Extensive comparisons of the quality of annealing of ion-implanted Si obtained with XeCl and ruby lasers have been made. The results indicate that irrespective of the large differences in the optical properties of Si at uv and visible wavelengths, the efficiency of usage of the incident energy for annealing is comparable for the two lasers. However, because of the excellent optical beam quality, the XeCl laser can provide superior control of the surface melting and the resulting junction depth. Furthermore, the concentrations of electrically active point defects in the XeCl laser annealed region are 2 to 3 orders of magnitude lower than that obtained from ruby or Nd:YAG lasers. All these results seem to suggest that XeCl lasers should be suitable for fabricating not only solar cells but also the more advanced device structures required for VLSI or VHSIC applications

  12. Bistable output from a coupled-resonator vertical-cavity laser diode

    International Nuclear Information System (INIS)

    Fischer, A. J.; Choquette, K. D.; Chow, W. W.; Allerman, A. A.; Geib, K.

    2000-01-01

    We report a monolithic coupled-resonator vertical-cavity laser with an ion-implanted top cavity and a selectively oxidized bottom cavity which exhibits bistable behavior in the light output versus injection current. Large bistability regions over current ranges as wide as 18 mA have been observed with on/off contrast ratios of greater than 20 dB. The position and width of the bistability region can be varied by changing the bias to the top cavity. Switching between on and off states can be accomplished with changes as small as 250 μW to the electrical power applied to the top cavity. The bistable behavior is the response of the nonlinear susceptibility in the top cavity to the changes in the bottom intracavity laser intensity as the bottom cavity reaches the thermal rollover point

  13. Bistable four-wave mixing response in a semiconductor quantum dot coupled to a photonic crystal nanocavity.

    Science.gov (United States)

    Li, Jian-Bo; Xiao, Si; Liang, Shan; He, Meng-Dong; Luo, Jian-Hua; Kim, Nam-Chol; Chen, Li-Qun

    2017-10-16

    We perform a theoretical study of the bistable four-wave mixing (FWM) response in a coupled system comprised of a semiconductor quantum dot (SQD) and a photonic crystal (PC) nanocavity in which the SQD is embedded. It is shown that the shape of the FWM spectrum can switch among single-peaked, double-peaked, triple-peaked, and four-peaked arising from the vacuum Rabi splitting and the exciton-nanocavity coupling. Especially, we map out bistability phase diagrams within a parameter subspace of the system, and find that it is easy to turn on or off the bistable FWM response by only adjusting the excitation frequency or the pumping intensity. Our results offer a feasible means for measuring the SQD-PC nanocavity coupling strength and open a new avenue to design optical switches and memories.

  14. Bistability of self-modulation oscillations in an autonomous solid-state ring laser

    International Nuclear Information System (INIS)

    Dudetskii, V Yu

    2013-01-01

    Bistable self-modulation regimes of generation for a ring YAG : Nd chip laser with the counterpropagating waves asymmetrically coupled via backward scattering are simulated numerically. Two branches of bistable self-modulation regimes of generation are found in the domain of the parametric resonance between the selfmodulation and relaxation oscillations. The self-modulation regimes observed in earlier experiments pertain to only one of the branches. Possible reasons for such a discrepancy are considered, related to the influence of technical and natural noise on the dynamics of solid-state ring lasers. (control of laser radiation parameters)

  15. Theory of semiconductor laser cooling

    Science.gov (United States)

    Rupper, Greg

    Recently laser cooling of semiconductors has received renewed attention, with the hope that a semiconductor cooler might be able to achieve cryogenic temperatures. In order to study semiconductor laser cooling at cryogenic temperatures, it is crucial that the theory include both the effects of excitons and the electron-hole plasma. In this dissertation, I present a theoretical analysis of laser cooling of bulk GaAs based on a microscopic many-particle theory of absorption and luminescence of a partially ionized electron-hole plasma. This theory has been analyzed from a temperature 10K to 500K. It is shown that at high temperatures (above 300K), cooling can be modeled using older models with a few parameter changes. Below 200K, band filling effects dominate over Auger recombination. Below 30K excitonic effects are essential for laser cooling. In all cases, excitonic effects make cooling easier then predicted by a free carrier model. The initial cooling model is based on the assumption of a homogeneous undoped semiconductor. This model has been systematically modified to include effects that are present in real laser cooling experiments. The following modifications have been performed. (1) Propagation and polariton effects have been included. (2) The effect of p-doping has been included. (n-doping can be modeled in a similar fashion.) (3) In experiments, a passivation layer is required to minimize non-radiative recombination. The passivation results in a npn heterostructure. The effect of the npn heterostructure on cooling has been analyzed. (4) The effect of a Gaussian pump beam was analyzed and (5) Some of the parameters in the cooling model have a large uncertainty. The effect of modifying these parameters has been analyzed. Most of the extensions to the original theory have only had a modest effect on the overall results. However we find that the current passivation technique may not be sufficient to allow cooling. The passivation technique currently used appears

  16. Semiconductor Lasers Stability, Instability and Chaos

    CERN Document Server

    Ohtsubo, Junji

    2013-01-01

    This third edition of “Semiconductor Lasers, Stability, Instability and Chaos” was significantly extended.  In the previous edition, the dynamics and characteristics of chaos in semiconductor lasers after the introduction of the fundamental theory of laser chaos and chaotic dynamics induced by self-optical feedback and optical injection was discussed. Semiconductor lasers with new device structures, such as vertical-cavity surface-emitting lasers and broad-area semiconductor lasers, are interesting devices from the viewpoint of chaotic dynamics since they essentially involve chaotic dynamics even in their free-running oscillations. These topics are also treated with respect to the new developments in the current edition. Also the control of such instabilities and chaos control are critical issues for applications. Another interesting and important issue of semiconductor laser chaos in this third edition is chaos synchronization between two lasers and the application to optical secure communication. One o...

  17. Semiconductor Lasers Stability, Instability and Chaos

    CERN Document Server

    Ohtsubo, Junji

    2008-01-01

    This monograph describes fascinating recent progress in the field of chaos, stability and instability of semiconductor lasers. Applications and future prospects are discussed in detail. The book emphasizes the various dynamics induced in semiconductor lasers by optical and electronic feedback, optical injection, and injection current modulation. Recent results of both theoretical and experimental investigations are presented. Demonstrating applications of semiconductor laser chaos, control and noise, Semiconductor Lasers describes suppression and chaotic secure communications. For those who are interested in optics but not familiar with nonlinear systems, a brief introduction to chaos analysis is presented.

  18. The transformation of optical bistability effect and of generated pulses in operation of a DFB laser with two sections

    International Nuclear Information System (INIS)

    Nguyen Van Phu; Dinh Van Hoang

    2005-01-01

    In this paper is presented the transformation of characteristics of optical bistability effect and of generated pulses in operation of a DFB laser with two sections. By solving the rate equations describing the operation of this laser the appearance of optical bistability effect in stationary regime and of short pulses in transient regime is obtained. With the variation of dynamical laser parameter we can evaluate the transformation indicated above. The method of examination used here is simple for determining the influence of any dynamical laser parameter on characteristics of optical bistability effect and generated pulses. (author)

  19. Chaotic bursting in semiconductor lasers

    Science.gov (United States)

    Ruschel, Stefan; Yanchuk, Serhiy

    2017-11-01

    We investigate the dynamic mechanisms for low frequency fluctuations in semiconductor lasers subjected to delayed optical feedback, using the Lang-Kobayashi model. This system of delay differential equations displays pronounced envelope dynamics, ranging from erratic, so called low frequency fluctuations to regular pulse packages, if the time scales of fast oscillations and envelope dynamics are well separated. We investigate the parameter regions where low frequency fluctuations occur and compute their Lyapunov spectra. Using the geometric singular perturbation theory, we study this intermittent chaotic behavior and characterize these solutions as bursting slow-fast oscillations.

  20. High brightness semiconductor lasers with reduced filamentation

    DEFF Research Database (Denmark)

    McInerney, John; O'Brien, Peter.; Skovgaard, Peter M. W.

    1999-01-01

    High brightness semiconductor lasers have applications in spectroscopy, fiber lasers, manufacturing and materials processing, medicine and free space communication or energy transfer. The main difficulty associated with high brightness is that, because of COD, high power requires a large aperture...

  1. Ultrafast laser-semiconductor interactions

    International Nuclear Information System (INIS)

    Schile, L.A.

    1996-01-01

    Studies of the ultrafast (< 100 fs) interactions of infrared, sub-100 fs laser pulses with IR, photosensitive semiconductor materials InGaAs, InSb, and HgCdTe are reported. Both the carrier dynamics and the associated Terahertz radiation from these materials are discussed. The most recent developments of femtosecond (< 100 fs) Optical Parametric Oscillators (OPO) has extended the wavelength range from the visible to 5.2 μm. The photogenerated semiconductor free carrier dynamics are determined in the 77 to 300 degrees K temperature range using the Transmission Correlation Peak (TCP) method. The electron-phonon scattering times are typically 200 - 600 fs. Depending upon the material composition and substrate on which the IR crystalline materials are deposited, the nonlinear TCP absorption gives recombination rates as fast as 10's of picoseconds. For the HgCdTe, there exists a 400 fs electron-phonon scattering process along with a much longer 3600 fs loss process. Studies of the interactions of these ultrashort laser pulses with semiconductors produce Terahertz (Thz) radiative pulses. With undoped InSb, there is a substantial change in the spectral content of this THz radiation between 80 - 260 degrees K while the spectrum of Te-doped InSb remains nearly unchanged, an effect attributed to its mobility being dominated by impurity scattering. At 80 degrees K, the terahertz radiation from undoped InSb is dependent on wavelength, with both a higher frequency spectrum and much larger amplitudes generated at longer wavelengths. No such effect is observed at 260 degrees K. Finally, new results on the dependence of the emitted THz radiation on the InSb crystal's orientation is presented

  2. Configurational rearrangements of bistable centers in covalent semiconductors - phase transitions of the second type

    International Nuclear Information System (INIS)

    Ivanyukovich, V.A.; Karas', V.I.; Lomako, V.M.

    1989-01-01

    A new radiation configurational-bistable defect diffring from the known similar defects by the fact that it possessestemperature inversion of states is detected in gallium arsenide. Configurational-bistable rearrangements are shown to be considered as phase transitions of the second type

  3. Progress in semiconductor laser diodes: SPIE volume 723

    International Nuclear Information System (INIS)

    Eichen, E.

    1987-01-01

    This book contains proceedings arranged under the following session headings: High power diode lasers; single emitters and arrays; Ultrahigh speed modulation of semiconductor diode lasers; Coherence and linewidth stabilized semiconductor lasers; and Growth, fabrication, and evaluation of laser diodes

  4. Controllable optical bistability in photonic-crystal one-atom laser

    International Nuclear Information System (INIS)

    Guo Xiaoyong; Lue Shuchen

    2009-01-01

    We investigate the property of optical bistability in a photonic-crystal one-atom laser when nonlinear microcavity is present. The physical system consists of a coherently driven two-level light emitter strongly coupled to a high-quality microcavity which is embedded within a photonic crystal and another coherent probing field which has incident into the microcavity. In our case, the microcavity is fabricated by nonlinear material and placed as an impurity in photonic crystal. This study reveals that such a system can exhibit optical bistability. The dependence of threshold value and hysteresis loop on the photonic band gap of the photonic crystal, driving field Rabi frequency and dephasing processes, are studied. Our results clearly illustrate the ability to control optical bistability through suitable photonic-crystal architectures and external coherent driving field, and this study suggests that in a photonic-crystal nonlinear microcavity, the one-atom laser acts as an effective controllable bistable device in the design of all-light digital computing systems in the near future.

  5. Frequency modulation of semiconductor disk laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Zolotovskii, I O; Korobko, D A; Okhotnikov, O G [Ulyanovsk State University, Ulyanovsk (Russian Federation)

    2015-07-31

    A numerical model is constructed for a semiconductor disk laser mode-locked by a semiconductor saturable absorber mirror (SESAM), and the effect that the phase modulation caused by gain and absorption saturation in the semiconductor has on pulse generation is examined. The results demonstrate that, in a laser cavity with sufficient second-order dispersion, alternating-sign frequency modulation of pulses can be compensated for. We also examine a model for tuning the dispersion in the cavity of a disk laser using a Gires–Tournois interferometer with limited thirdorder dispersion. (control of radiation parameters)

  6. Laser Cooling of 2-6 Semiconductors

    Science.gov (United States)

    2016-08-12

    AFRL-AFOSR-JP-TR-2016-0067 Laser Cooling of II-VI Semiconductors Qihua Xiong NANYANG TECHNOLOGICAL UNIVERSITY Final Report 08/12/2016 DISTRIBUTION A...From - To) 15 May 2013 to 14 May 2016 4. TITLE AND SUBTITLE Laser Cooling of II-VI Semiconductors 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA2386-13-1...13. SUPPLEMENTARY NOTES 14. ABSTRACT The breakthrough of laser cooling in semiconductor has stimulated strong interest in further scaling up towards

  7. Wavelength switching dynamics of two-colour semiconductor lasers with optical injection and feedback

    International Nuclear Information System (INIS)

    Osborne, S; Heinricht, P; Brandonisio, N; Amann, A; O’Brien, S

    2012-01-01

    The wavelength switching dynamics of two-colour semiconductor lasers with optical injection and feedback are presented. These devices incorporate slotted regions etched into the laser ridge waveguide for tailoring the output spectrum. Experimental measurements are presented demonstrating that optical injection in one or both modes of these devices can induce wavelength bistability. Measured switching dynamics with modulated optical injection are shown to be in excellent agreement with numerical simulations based on a simple rate equation model. We also demonstrate experimentally that time-delayed optical feedback can induce wavelength bistability for short external cavity lengths. Numerical simulations indicate that this two-colour optical feedback system can provide fast optical memory functionality based on injected optical pulses without the need for an external holding beam. (paper)

  8. Study on guided waves in semiconductor lasers

    International Nuclear Information System (INIS)

    Pudensi, M.A.A.

    1980-01-01

    In This work we studied the guided waves in semiconductor lasers. In the first part we carried on the experimental measurements on lasers with stripe nonorthogonal to the mirrors. In the second part we developed a matrix method for the study of propagation and reflection of guided waves in lasers. (author) [pt

  9. Bistable optical devices with laser diodes coupled to absorbers of narrow spectral bandwidth.

    Science.gov (United States)

    Maeda, Y

    1994-06-20

    An optical signal inverter was demonstrated with a combination of the following two effects: One is the decrease of the transmission of an Er-doped YAG crystal with increasing red shift of a laser diode resulting from an increase in the injection current, and the other is a negative nonlinear absorption in which the transmission decreases inversely with increasing laser intensity. Because a hysteresis characteristic exists in the relationship between the wavelength and the injection current of the laser diode, an optical bistability was observed in this system.

  10. Optical bistability in erbium-doped yttrium aluminum garnet crystal combined with a laser diode.

    Science.gov (United States)

    Maeda, Y

    1994-01-10

    Optical bistability was observed in a simple structure of an injection laser diode combined with an erbium-doped yttrium aluminum garnet crystal. Since a hysteresis characteristic exists in the relationship between the wavelength and the injection current of a laser diode, an optical memory function capable of holding the output status is confirmed. In addition, an optical signal inversion was caused by the decrease of transmission of the erbium-doped yttrium aluminum garnet crystal against the red shift (principally mode hopping) of the laser diode. It is suggested that the switching time of this phenomenon is the time necessary for a mode hopping by current injection.

  11. Effect of gain nonlinearity in semiconductor lasers

    DEFF Research Database (Denmark)

    Jensen, Niels H.; Christiansen, Peter Leth; Skovgaard, Ove

    1988-01-01

    Semiconductor lasers are modeled by single-mode rate equations with Langevin noise terms and the influence of nonlinear gain is investigated. For cw operation the probability distribution for the carrier number and the photon number in the laser cavity is obtained. The corresponding (2+1)-dimensi......Semiconductor lasers are modeled by single-mode rate equations with Langevin noise terms and the influence of nonlinear gain is investigated. For cw operation the probability distribution for the carrier number and the photon number in the laser cavity is obtained. The corresponding (2...

  12. Laser vapor phase deposition of semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Karlov, N.V.; Luk' ianchuk, B.S.; Sisakian, E.V.; Shafeev, G.A.

    1987-06-01

    The pyrolytic effect of IR laser radiation is investigated with reference to the initiation and control of the vapor phase deposition of semiconductor films. By selecting the gas mixture composition and laser emission parameters, it is possible to control the deposition and crystal formation processes on the surface of semiconductors, with the main control action achieved due to the nonadiabatic kinetics of reactions in the gas phase and high temperatures in the laser heating zone. This control mechanism is demonstrated experimentally during the laser vapor deposition of germanium and silicon films from tetrachlorides on single-crystal Si and Ge substrates. 5 references.

  13. Semiconductor laser technology for remote sensing experiments

    Science.gov (United States)

    Katz, Joseph

    1988-01-01

    Semiconductor injection lasers are required for implementing virtually all spaceborne remote sensing systems. Their main advantages are high reliability and efficiency, and their main roles are envisioned in pumping and injection locking of solid state lasers. In some shorter range applications they may even be utilized directly as the sources.

  14. Semiconductor laser using multimode interference principle

    Science.gov (United States)

    Gong, Zisu; Yin, Rui; Ji, Wei; Wu, Chonghao

    2018-01-01

    Multimode interference (MMI) structure is introduced in semiconductor laser used in optical communication system to realize higher power and better temperature tolerance. Using beam propagation method (BPM), Multimode interference laser diode (MMI-LD) is designed and fabricated in InGaAsP/InP based material. As a comparison, conventional semiconductor laser using straight single-mode waveguide is also fabricated in the same wafer. With a low injection current (about 230 mA), the output power of the implemented MMI-LD is up to 2.296 mW which is about four times higher than the output power of the conventional semiconductor laser. The implemented MMI-LD exhibits stable output operating at the wavelength of 1.52 μm and better temperature tolerance when the temperature varies from 283.15 K to 293.15 K.

  15. Semiconductor Laser Tracking Frequency Distance Gauge

    Science.gov (United States)

    Phillips, James D.; Reasenberg, Robert D.

    2009-01-01

    Advanced astronomical missions with greatly enhanced resolution and physics missions of unprecedented accuracy will require a spaceworthy laser distance gauge of substantially improved performance. The Tracking Frequency Gauge (TFG) uses a single beam, locking a laser to the measurement interferometer. We have demonstrated this technique with pm (10(exp -12) m) performance. We report on the version we are now developing based on space-qualifiable, fiber-coupled distributed-feedback semiconductor lasers.

  16. Functional integrity of flexible n-channel metal–oxide–semiconductor field-effect transistors on a reversibly bistable platform

    Energy Technology Data Exchange (ETDEWEB)

    Alfaraj, Nasir; Hussain, Aftab M.; Torres Sevilla, Galo A.; Ghoneim, Mohamed T.; Rojas, Jhonathan P.; Hussain, Muhammad M., E-mail: MuhammadMustafa.Hussain@kaust.edu.sa [Integrated Nanotechnology Laboratory, Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900 (Saudi Arabia); Aljedaani, Abdulrahman B. [High-Speed Fluids Imaging Laboratory, Physical Sciences and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900 (Saudi Arabia)

    2015-10-26

    Flexibility can bring a new dimension to state-of-the-art electronics, such as rollable displays and integrated circuit systems being transformed into more powerful resources. Flexible electronics are typically hosted on polymeric substrates. Such substrates can be bent and rolled up, but cannot be independently fixed at the rigid perpendicular position necessary to realize rollable display-integrated gadgets and electronics. A reversibly bistable material can assume two stable states in a reversible way: flexibly rolled state and independently unbent state. Such materials are used in cycling and biking safety wristbands and a variety of ankle bracelets for orthopedic healthcare. They are often wrapped around an object with high impulsive force loading. Here, we study the effects of cumulative impulsive force loading on thinned (25 μm) flexible silicon-based n-channel metal–oxide–semiconductor field-effect transistor devices housed on a reversibly bistable flexible platform. We found that the transistors have maintained their high performance level up to an accumulated 180 kN of impact force loading. The gate dielectric layers have maintained their reliability, which is evidenced by the low leakage current densities. Also, we observed low variation in the effective electron mobility values, which manifests that the device channels have maintained their carrier transport properties.

  17. Functional integrity of flexible n-channel metal–oxide–semiconductor field-effect transistors on a reversibly bistable platform

    International Nuclear Information System (INIS)

    Alfaraj, Nasir; Hussain, Aftab M.; Torres Sevilla, Galo A.; Ghoneim, Mohamed T.; Rojas, Jhonathan P.; Hussain, Muhammad M.; Aljedaani, Abdulrahman B.

    2015-01-01

    Flexibility can bring a new dimension to state-of-the-art electronics, such as rollable displays and integrated circuit systems being transformed into more powerful resources. Flexible electronics are typically hosted on polymeric substrates. Such substrates can be bent and rolled up, but cannot be independently fixed at the rigid perpendicular position necessary to realize rollable display-integrated gadgets and electronics. A reversibly bistable material can assume two stable states in a reversible way: flexibly rolled state and independently unbent state. Such materials are used in cycling and biking safety wristbands and a variety of ankle bracelets for orthopedic healthcare. They are often wrapped around an object with high impulsive force loading. Here, we study the effects of cumulative impulsive force loading on thinned (25 μm) flexible silicon-based n-channel metal–oxide–semiconductor field-effect transistor devices housed on a reversibly bistable flexible platform. We found that the transistors have maintained their high performance level up to an accumulated 180 kN of impact force loading. The gate dielectric layers have maintained their reliability, which is evidenced by the low leakage current densities. Also, we observed low variation in the effective electron mobility values, which manifests that the device channels have maintained their carrier transport properties

  18. Functional integrity of flexible n-channel metal–oxide–semiconductor field-effect transistors on a reversibly bistable platform

    KAUST Repository

    Alfaraj, Nasir; Hussain, Aftab M.; Torres Sevilla, Galo A.; Ghoneim, Mohamed T.; Rojas, Jhonathan Prieto; Aljedaani, Abdulrahman B.; Hussain, Muhammad Mustafa

    2015-01-01

    Flexibility can bring a new dimension to state-of-the-art electronics, such as rollable displays and integrated circuit systems being transformed into more powerful resources. Flexible electronics are typically hosted on polymeric substrates. Such substrates can be bent and rolled up, but cannot be independently fixed at the rigid perpendicular position necessary to realize rollable display-integrated gadgets and electronics. A reversibly bistable material can assume two stable states in a reversible way: flexibly rolled state and independently unbent state. Such materials are used in cycling and biking safety wristbands and a variety of ankle bracelets for orthopedic healthcare. They are often wrapped around an object with high impulsive force loading. Here, we study the effects of cumulative impulsive force loading on thinned (25 μm) flexible silicon-based n-channel metal–oxide–semiconductor field-effect transistor devices housed on a reversibly bistable flexible platform. We found that the transistors have maintained their high performance level up to an accumulated 180 kN of impact force loading. The gate dielectric layers have maintained their reliability, which is evidenced by the low leakage current densities. Also, we observed low variation in the effective electron mobility values, which manifests that the device channels have maintained their carrier transport properties.

  19. Functional integrity of flexible n-channel metal-oxide-semiconductor field-effect transistors on a reversibly bistable platform

    Science.gov (United States)

    Alfaraj, Nasir; Hussain, Aftab M.; Torres Sevilla, Galo A.; Ghoneim, Mohamed T.; Rojas, Jhonathan P.; Aljedaani, Abdulrahman B.; Hussain, Muhammad M.

    2015-10-01

    Flexibility can bring a new dimension to state-of-the-art electronics, such as rollable displays and integrated circuit systems being transformed into more powerful resources. Flexible electronics are typically hosted on polymeric substrates. Such substrates can be bent and rolled up, but cannot be independently fixed at the rigid perpendicular position necessary to realize rollable display-integrated gadgets and electronics. A reversibly bistable material can assume two stable states in a reversible way: flexibly rolled state and independently unbent state. Such materials are used in cycling and biking safety wristbands and a variety of ankle bracelets for orthopedic healthcare. They are often wrapped around an object with high impulsive force loading. Here, we study the effects of cumulative impulsive force loading on thinned (25 μm) flexible silicon-based n-channel metal-oxide-semiconductor field-effect transistor devices housed on a reversibly bistable flexible platform. We found that the transistors have maintained their high performance level up to an accumulated 180 kN of impact force loading. The gate dielectric layers have maintained their reliability, which is evidenced by the low leakage current densities. Also, we observed low variation in the effective electron mobility values, which manifests that the device channels have maintained their carrier transport properties.

  20. Teradiode's high brightness semiconductor lasers

    Science.gov (United States)

    Huang, Robin K.; Chann, Bien; Burgess, James; Lochman, Bryan; Zhou, Wang; Cruz, Mike; Cook, Rob; Dugmore, Dan; Shattuck, Jeff; Tayebati, Parviz

    2016-03-01

    TeraDiode is manufacturing multi-kW-class ultra-high brightness fiber-coupled direct diode lasers for industrial applications. A fiber-coupled direct diode laser with a power level of 4,680 W from a 100 μm core diameter, BPP) of 3.5 mm-mrad and is the lowest BPP multi-kW-class direct diode laser yet reported. This laser is suitable for industrial materials processing applications, including sheet metal cutting and welding. This 4-kW fiber-coupled direct diode laser has comparable brightness to that of industrial fiber lasers and CO2 lasers, and is over 10x brighter than state-of-the-art direct diode lasers. We have also demonstrated novel high peak power lasers and high brightness Mid-Infrared Lasers.

  1. The theory of stability, bistability, and instability in three-mode class-A lasers

    International Nuclear Information System (INIS)

    Jahanpanah, J; Rahdar, A A

    2014-01-01

    Instability is an inevitable and common problem in all different kinds of lasers when they are oscillating in both single-and multi-mode states. Here, the stability conditions are investigated for a three-mode class-A laser. A set of linear equations is derived for the stable oscillation of the cavity central mode together with its left and right adjacent longitudinal modes. The coefficient determinant of stability equations is Hermitian and equal to zero for the roots of two diagonal arrays. In other words, the novelty of our work is to expand the stability coefficient determinant in terms of main diagonal arrays rather than for one row or one column. These diagonal roots lead to two lower and upper boundary curves in the form of a bifurcation. The lower boundary curve mimics the single-mode laser and delimits the instability region (with no above-threshold oscillating mode) from the bistability region (with two above-threshold oscillating modes). The upper boundary curve mimics the two-mode laser and delimits the bistability region from the stability region, in which all three-longitudinal modes are simultaneously oscillating in the above-threshold state. (paper)

  2. Phase-dependent optical bistability and multistability in a semiconductor quantum well system

    International Nuclear Information System (INIS)

    Wang Zhiping; Fan Hongyi

    2010-01-01

    We theoretically investigate the hybrid absorptive-dispersive optical bistability and multistability in a four-level inverted-Y quantum well system inside a unidirectional ring cavity. We find that the coupling field, the pumping field as well as the cycling field can affect the optical bistability and multistability dramatically, which can be used to manipulate efficiently the threshold intensity and the hysteresis loop. The effects of the relative phase and the electronic cooperation parameter on the OB and OM are also studied. Our study is much more practical than its atomic counterpart due to its flexible design and the wide adjustable parameters. Thus, it may provide some new possibilities for technological applications in optoelectronics and solid-state quantum information science.

  3. Reduced filamentation in high power semiconductor lasers

    DEFF Research Database (Denmark)

    Skovgaard, Peter M. W.; McInerney, John; O'Brien, Peter

    1999-01-01

    High brightness semiconductor lasers have applications in fields ranging from material processing to medicine. The main difficulty associated with high brightness is that high optical power densities cause damage to the laser facet and thus require large apertures. This, in turn, results in spatio......-temporal instabilities such as filamentation which degrades spatial coherence and brightness. We first evaluate performance of existing designs with a “top-hat” shaped transverse current density profile. The unstable nature of highly excited semiconductor material results in a run-away process where small modulations...

  4. Bistability of Pulsating Intensities for Double-Locked Laser Diodes

    National Research Council Canada - National Science Library

    Erneux, Thomas

    2004-01-01

    .... The investigation will concentrate on two Edifferential Cavity mode (ECM) solutions of the laser rate equations, because coupling might lead to high-frequency intensity oscillations. The objective is to determine the conditions for stability of these solutions. Conclusions will be tested by numerical bifurcation studies.

  5. Bistable direction switching in an off-axis pumped continuous wave ruby laser

    Science.gov (United States)

    Afzal, R. Sohrab; Lawandy, N. M.

    1988-01-01

    A report is presented of the observation of hysteretic bistable direction switching in a single-mode CW ruby laser system. This effect is only observed when the pump beam which is focused into the ruby rod is misaligned with respect to the rod end faces. At low pump powers, the ruby lases in a mode nearly collinear with the pump axis. At a higher pump power the ruby switches to a mode that is collinear with the rod end faces and preserves the original polarization. The effect is large enough to switch the beam by an angle equal to twice the diffraction angle. The observations show that under steady-state pumping, a CW ruby laser can exhibit bistable operation in its output direction and power. A calculation using the heat equation with two concentric cylinders with one as a heat source (pump laser) and the outer wall of the other held at 77 K, gives an increase in core temperature of about 0.01 K. Therefore, the increase in temperature is not large enough to change the index of refraction to account for such large macroscopic effects.

  6. MBE System for Antimonide Based Semiconductor Lasers

    National Research Council Canada - National Science Library

    Lester, Luke

    1999-01-01

    .... SLR-770 inductively coupled plasma (ICP) processing system. The SLR-770 has been invaluable in the study of plasma etching of AlGaAsSb and GaSb-materials that form the backbone of antimonide-based semiconductor lasers...

  7. Air-stable memory array of bistable rectifying diodes based on ferroelectric-semiconductor polymer blends

    Science.gov (United States)

    Kumar, Manasvi; Sharifi Dehsari, Hamed; Anwar, Saleem; Asadi, Kamal

    2018-03-01

    Organic bistable diodes based on phase-separated blends of ferroelectric and semiconducting polymers have emerged as promising candidates for non-volatile information storage for low-cost solution processable electronics. One of the bottlenecks impeding upscaling is stability and reliable operation of the array in air. Here, we present a memory array fabricated with an air-stable amine-based semiconducting polymer. Memory diode fabrication and full electrical characterizations were carried out in atmospheric conditions (23 °C and 45% relative humidity). The memory diodes showed on/off ratios greater than 100 and further exhibited robust and stable performance upon continuous write-read-erase-read cycles. Moreover, we demonstrate a 4-bit memory array that is free from cross-talk with a shelf-life of several months. Demonstration of the stability and reliable air operation further strengthens the feasibility of the resistance switching in ferroelectric memory diodes for low-cost applications.

  8. E-beam-pumped semiconductor lasers

    Science.gov (United States)

    Rice, Robert R.; Shanley, James F.; Ruggieri, Neil F.

    1995-04-01

    The collapse of the Soviet Union opened many areas of laser technology to the West. E-beam- pumped semiconductor lasers (EBSL) were pursued for 25 years in several Soviet Institutes. Thin single crystal screens of II-VI alloys (ZnxCd1-xSe, CdSxSe1-x) were incorporated in laser CRTs to produce scanned visible laser beams at average powers greater than 10 W. Resolutions of 2500 lines were demonstrated. MDA-W is conducting a program for ARPA/ESTO to assess EBSL technology for high brightness, high resolution RGB laser projection application. Transfer of II-VI crystal growth and screen processing technology is underway, and initial results will be reported. Various techniques (cathodoluminescence, one- and two-photon laser pumping, etc.) have been used to assess material quality and screen processing damage. High voltage (75 kV) video electronics were procured in the U.S. to operate test EBSL tubes. Laser performance was documented as a function of screen temperature, beam voltage and current. The beam divergence, spectrum, efficiency and other characteristics of the laser output are being measured. An evaluation of the effect of laser operating conditions upon the degradation rate is being carried out by a design-of-experiments method. An initial assessment of the projected image quality will be performed.

  9. Asymmetrically excited semiconductor injection laser

    International Nuclear Information System (INIS)

    Ladany, I.; Marinelli, D.P.; Kressel, H.; Cannuli, V.M.

    1975-01-01

    A diode laser is improved in order to produce an output in a single longitudinal mode. The laser has a rectangular body with two regions of differing conductivity type material. Extending from one surface of the rectangular body and into one of the regions of differing conductivity material is a third region. Although the third region is composed of the same general conductivity type material as the region into which it extends, it is more highly doped with conductivity modifiers (more conductive). This third region extends along one surface between the ends of the body and is spaced from the sides of the body. An electrical contact stripe is positioned on the one surface so that a portion of its width overlaps a portion of the width of the third region

  10. Semiconductor lasers in rheumatological treatment

    Science.gov (United States)

    Pascu, Mihail-Lucian; Suteanu, S.; Ignat, P.; Pruna, Simion; Chitu, A.

    1995-03-01

    A computer controlled equipment, containing 6 lasers (HeNe and 5 diode lasers--DL) conceived to be used in rheumatological treatment is reported. DL emit at 895 nm and for typical applications, their expanded spots are superposed within the irradiation plane, on the HeNE defocused spot used to define the surface to be irradiated. DL emit 100 nsec pulses between 0.5 KHz and 1.5 KHz repetition rate and 0.5 mW average power (measured at 1 KHz). 150 patients with rheumathologic diseases were treated: lumbar spondylosis (75), gonarthrosis (30), cervical spondylosis (21), coxarthrosis (15), Heberden and Bouchard (9). The treatment consisted of: group I, 50 patients--laser therapy, 10 min/day, 10 days; group II, 50 patients--classical antirheumatic treatment; group III, 50 patients--mixed treatment. Assessment of sympathetic skin activity made using reactometry measurements, shows that latency time was longer before irradiation, 1867 +/- 289) msec then after, (1234 +/- 321) msec. Pain rating indexes decreasing for all three groups of patients were measured. Better results for more superficial diseases were obtained and best results were observed after irradiation with 1 KHz - 1.5 KHz repetition rate IR pulses. Better results were obtained when spot irradiation in a few points combined with zone irradiations was used.

  11. Optical double-locked semiconductor lasers

    Science.gov (United States)

    AlMulla, Mohammad

    2018-06-01

    Self-sustained period-one (P1) nonlinear dynamics of a semiconductor laser are investigated when both optical injection and modulation are applied for stable microwave frequency generation. Locking the P1 oscillation through modulation on the bias current, injection strength, or detuning frequency stabilizes the P1 oscillation. Through the phase noise variance, the different modulation types are compared. It is demonstrated that locking the P1 oscillation through optical modulation on the output of the master laser outperforms bias-current modulation of the slave laser. Master laser modulation shows wider P1-oscillation locking range and lower phase noise variance. The locking characteristics of the P1 oscillation also depend on the operating conditions of the optical injection system

  12. Squeezing in an injection-locked semiconductor laser

    Science.gov (United States)

    Inoue, S.; Machida, S.; Yamamoto, Y.; Ohzu, H.

    1993-09-01

    The intensity-noise properties of an injection-locked semiconductor laser were studied experimentally. The constant-current-driven semiconductor laser producing the amplitude-squeezed state whose intensity noise was reduced below the standard quantum limit (SQL) by 0.72 dB was injection-locked by an external master laser. The measured intensity-noise level of the injection-locked semiconductor laser was 0.91 dB below the SQL. This experimental result indicates that a phase-coherent amplitude-squeezed state or squeezed vacuum state together with a reference local oscillator wave can be generated directly by semiconductor laser systems.

  13. EDITORIAL: Semiconductor lasers: the first fifty years Semiconductor lasers: the first fifty years

    Science.gov (United States)

    Calvez, S.; Adams, M. J.

    2012-09-01

    Anniversaries call for celebrations. Since it is now fifty years since the first semiconductor lasers were reported, it is highly appropriate to celebrate this anniversary with a Special Issue dedicated to the topic. The semiconductor laser now has a major effect on our daily lives since it has been a key enabler in the development of optical fibre communications (and hence the internet and e-mail), optical storage (CDs, DVDs, etc) and barcode scanners. In the early 1960s it was impossible for most people (with the exception of very few visionaries) to foresee any of these future developments, and the first applications identified were for military purposes (range-finders, target markers, etc). Of course, many of the subsequent laser applications were made possible by developments in semiconductor materials, in the associated growth and fabrication technology, and in the increased understanding of the underlying fundamental physics. These developments continue today, so that the subject of semiconductor lasers, although mature, is in good health and continues to grow. Hence, we can be confident that the pervasive influence of semiconductor lasers will continue to develop as optoelectronics technology makes further advances into other sectors such as healthcare, security and a whole host of applications based on the global imperatives to reduce energy consumption, minimise environmental impact and conserve resources. The papers in this Special Issue are intended to tell some of the story of the last fifty years of laser development as well as to provide evidence of the current state of semiconductor laser research. Hence, there are a number of papers where the early developments are recalled by authors who played prominent parts in the story, followed by a selection of papers from authors who are active in today's exciting research. The twenty-fifth anniversary of the semiconductor laser was celebrated by the publication of a number of papers dealing with the early

  14. The features of modelling semiconductor lasers with a wide contact

    Directory of Open Access Journals (Sweden)

    Rzhanov Alexey

    2017-01-01

    Full Text Available The aspects of calculating the dynamics and statics of powerful semiconductor laser diodes radiation are investigated. It takes into account the main physical mechanisms influencing power, spectral composition, far and near field of laser radiation. It outlines a dynamic distributed model of a semiconductor laser with a wide contact and possible algorithms for its implementation.

  15. The pursuit of electrically-driven organic semiconductor lasers

    NARCIS (Netherlands)

    Bisri, Satria Zulkarnaen; Takenobu, Taishi; Iwasa, Yoshihiro

    2014-01-01

    Organic semiconductors have many favourable and plastic-like optical properties that are promising for the development of low energy consuming laser devices. Although optically-pumped organic semiconductor lasers have been demonstrated since the early days of lasers, electrically-driven organic

  16. Hybrid optoelectronic device with multiple bistable outputs

    Energy Technology Data Exchange (ETDEWEB)

    Costazo-Caso, Pablo A; Jin Yiye; Gelh, Michael; Granieri, Sergio; Siahmakoun, Azad, E-mail: pcostanzo@ing.unlp.edu.are, E-mail: granieri@rose-hulma.edu, E-mail: siahmako@rose-hulma.edu [Department of Physics and Optical Engineering, Rose-Hulman Institute of Technology, 5500 Wabash Avenue, Terre Haute, IN 47803 (United States)

    2011-01-01

    Optoelectronic circuits which exhibit optical and electrical bistability with hysteresis behavior are proposed and experimentally demonstrated. The systems are based on semiconductor optical amplifiers (SOA), bipolar junction transistors (BJT), PIN photodiodes (PD) and laser diodes externally modulated with integrated electro-absorption modulators (LD-EAM). The device operates based on two independent phenomena leading to both electrical bistability and optical bistability. The electrical bistability is due to the series connection of two p-i-n structures (SOA, BJT, PD or LD) in reverse bias. The optical bistability is consequence of the quantum confined Stark effect (QCSE) in the multi-quantum well (MQW) structure in the intrinsic region of the device. This effect produces the optical modulation of the transmitted light through the SOA (or reflected from the PD). Finally, because the optical transmission of the SOA (in reverse bias) and the reflected light from the PD are so small, a LD-EAM modulated by the voltage across these devices are employed to obtain a higher output optical power. Experiments show that the maximum switching frequency is in MHz range and the rise/fall times lower than 1 us. The temporal response is mainly limited by the electrical capacitance of the devices and the parasitic inductances of the connecting wires. The effects of these components can be reduced in current integration technologies.

  17. Melting phenomenon and laser annealing in semiconductors

    International Nuclear Information System (INIS)

    Narayan, J.

    1981-03-01

    The work on annealing of displacement damage, dissolution of boron precipitates, and the broadening of dopant profiles in semiconductors after treating with ruby and dye laser pulses is reviewed in order to provide convincing evidence for the melting phenomenon and illustrate the mechanism associated with laser annealing. The nature of the solid-liquid interface and the interface instability during rapid solidification is considered in detail. It is shown that solute concentrations after pulsed laser annealing can far exceed retrograde maxima values. However, there is a critical solute concentration above which a planar solid-liquid interface becomes unstable and breaks into a cellular structure. The solute concentrations and cell sizes associated with this instability are calculated using a perturbation theory, and compared with experimental results

  18. Amplification of an Autodyne Signal in a Bistable Vertical-Cavity Surface-Emitting Laser with the Use of a Vibrational Resonance

    Science.gov (United States)

    Chizhevsky, V. N.

    2018-01-01

    For the first time, it is demonstrated experimentally that a vibrational resonance in a polarization-bistable vertical-cavity surface-emitting laser can be used to increase the laser response in autodyne detection of microvibrations from reflecting surfaces. In this case, more than 25-fold signal amplification is achieved. The influence of the asymmetry of the bistable potential on the microvibration-detection efficiency is studied.

  19. What is refractive optical bistability

    International Nuclear Information System (INIS)

    Dzhehov, Tomislav

    1993-01-01

    The basic elements of the theory of refractive optical bistability, assuming mediums with linear absorption are given. Special attention is paid to bistable etalons of semiconductor materials an oxide glasses, since some of them are considered as promising components for optical bistability applications. The design optimization of such devices for minimum switching intensity is analyzed. Computer simulation of the transfer characteristic recording for two InSb etalons is presented. (author)

  20. Piezoelectric strained layer semiconductor lasers and integrated modulators

    International Nuclear Information System (INIS)

    Fleischmann, Thomas

    2002-01-01

    The properties, benefits and limitations of strained InGaAs/GaAs quantum well lasers and modulators grown on (111)B GaAs have been studied. Particular interest in this material system arose from the predicted increase in critical layer thickness, which would facilitate semiconductor lasers emitting beyond 1 μm. However, the recent discovery of a new type of misfit dislocation indicates that the critical layer thickness in this system is closer to that of (001) orientated structures. Photoluminescence and transmission electron microscopy presented in this study support this predicted reduction of the critical layer thickness and the resulting limitations on the emission wavelength. The absence of 3D growth in this system may however be advantageous when high reproducibility and reliable lasing operation beyond 1 μm are required. The piezoelectric field originating from strained growth on substrate orientations other than (001) was studied and its influence on transition energies and absorptive behaviour were investigated. The piezoelectric constant was found to show significant temperature dependence and, as also indicated in earlier studies, its value is smaller then the linearly interpolated value. When the effects of indium segregation on the transition energies is considered, the reduction is significantly smaller. Good agreement between theory and experiment was obtained using 86% of the value linearly interpolated between the binaries at room temperature and 82% at low temperature. Broad area lasers were fabricated emitting at lasing wavelengths of up to 1.08 μm with threshold current densities as low as 80 A/cm 2 at room temperature under continuous wave operation. Increasing the indium composition and strain within the limit of strain relaxation was demonstrated to improve device performance significantly. Furthermore, ridge waveguide lasers were fabricated exhibiting monomode emission at wavelengths up to 1.07 μm with a threshold current of 19 mA at

  1. Optically induced bistable states in metal/tunnel-oxide/semiconductor /MTOS/ junctions

    Science.gov (United States)

    Lai, S. K.; Dressendorfer, P. V.; Ma, T. P.; Barker, R. C.

    1981-01-01

    A new switching phenomenon in metal-oxide semiconductor tunnel junction has been discovered. With a sufficiently large negative bias applied to the electrode, incident visible light of intensity greater than about 1 microW/sq cm causes the reverse-biased junction to switch from a low-current to a high-current state. It is believed that hot-electron-induced impact ionization provides the positive feedback necessary for switching, and causes the junction to remain in its high-current state after the optical excitation is removed. The junction may be switched back to the low-current state electrically. The basic junction characteristics have been measured, and a simple model for the switching phenomenon has been developed.

  2. CO2 laser pulse switching by optically excited semiconductors

    International Nuclear Information System (INIS)

    Silva, V.L. da.

    1986-01-01

    The construction and the study of a semi-conductor optical switch used for generating short infrared pulses and to analyse the semiconductor characteristics, are presented. The switch response time depends on semiconductor and control laser characteristics. The results obtained using a Ge switch controlled by N 2 , NdYag and Dye lasers are presented. The response time was 50 ns limited by Ge recombination time. The reflectivity increased from 7% to 59% using N 2 laser to control the switch. A simple model for semiconductor optical properties that explain very well the experimental results, is also presented. (author) [pt

  3. The Modulation Response of a Semiconductor Laser Amplifier

    DEFF Research Database (Denmark)

    Mørk, Jesper; Mecozzi, Antonio; Eisenstein, Gadi

    1999-01-01

    We present a theoretical analysis of the modulation response of a semiconductor laser amplifier. We find a resonance behavior similar to the well-known relaxation oscillation resonance found in semiconductor lasers, but of a different physical origin. The role of the waveguide (scattering) loss i...

  4. Modelling colliding-pulse mode-locked semiconductor lasers

    DEFF Research Database (Denmark)

    Bischoff, Svend

    or to determine the optimum operation conditions. The purpose of this thesis is to elucidate some of the physics of interest in the field of semiconductor laser modelling, semiconductor optics and fiber optics. To be more specific we will investigate: The Colliding-Pulse Mode-Locked (CPM) Quantum Well (QW) laser...... diode; the excitonic semiconductor response for varying material thickness in the case of linear optics; and modulational instability of electromagnetic waves in media with spatially varying non-linearity....

  5. Semiconductor Laser Diode Pumps for Inertial Fusion Energy Lasers

    International Nuclear Information System (INIS)

    Deri, R.J.

    2011-01-01

    Solid-state lasers have been demonstrated as attractive drivers for inertial confinement fusion on the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) and at the Omega Facility at the Laboratory for Laser Energetics (LLE) in Rochester, NY. For power plant applications, these lasers must be pumped by semiconductor diode lasers to achieve the required laser system efficiency, repetition rate, and lifetime. Inertial fusion energy (IFE) power plants will require approximately 40-to-80 GW of peak pump power, and must operate efficiently and with high system availability for decades. These considerations lead to requirements on the efficiency, price, and production capacity of the semiconductor pump sources. This document provides a brief summary of these requirements, and how they can be met by a natural evolution of the current semiconductor laser industry. The detailed technical requirements described in this document flow down from a laser ampl9ifier design described elsewhere. In brief, laser amplifiers comprising multiple Nd:glass gain slabs are face-pumped by two planar diode arrays, each delivering 30 to 40 MW of peak power at 872 nm during a ∼ 200 (micro)s quasi-CW (QCW) pulse with a repetition rate in the range of 10 to 20 Hz. The baseline design of the diode array employs a 2D mosaic of submodules to facilitate manufacturing. As a baseline, they envision that each submodule is an array of vertically stacked, 1 cm wide, edge-emitting diode bars, an industry standard form factor. These stacks are mounted on a common backplane providing cooling and current drive. Stacks are conductively cooled to the backplane, to minimize both diode package cost and the number of fluid interconnects for improved reliability. While the baseline assessment in this document is based on edge-emitting devices, the amplifier design does not preclude future use of surface emitting diodes, which may offer appreciable future cost reductions and

  6. The astigmatism factor for semiconductor injection lasers

    International Nuclear Information System (INIS)

    Zhao Yiguang; Guo Changzhi

    1988-03-01

    The relations between the astigmatism factor and the waveguide structure, working conditions etc. were accurately calculated, using a method for deriving a self-consistent solution of the optical field equation and the carrier diffusion equation. Various theoretical models regarding the spontaneous emission factor were analyzed and compared. The results show that there is a difference between astigmatism factors of semiconductor lasers with different waveguide structures. W. Streifer's results, for a model having an invariable distribution of the complex refractive index, are larger by a factor of 6 to 80 than the accurate calculated value. K. Petermann's theory regarding the spontaneous emission factor is more appropriate than other theories. (author). 19 refs, 6 figs

  7. Below-bandgap photoreflection spectroscopy of semiconductor laser structures

    International Nuclear Information System (INIS)

    Sotnikov, Aleksandr E; Chernikov, Maksim A; Ryabushkin, Oleg A; Trubenko, P; Moshegov, N; Ovchinnikov, A

    2004-01-01

    A new method of modulated light reflection - below-bandgap photoreflection, is considered. Unlike the conventional photoreflection method, the proposed method uses optical pumping by photons of energy smaller than the bandgap of any layer of a semiconductor structure under study. Such pumping allows one to obtain the modulated reflection spectrum for all layers of the structure without excitation of photoluminescence. This method is especially promising for the study of wide-gap semiconductors. The results of the study of semiconductor structures used in modern high-power multimode semiconductor lasers are presented. (laser applications and other topics in quantum electronics)

  8. Ring cavity surface emitting semiconductor lasers

    International Nuclear Information System (INIS)

    Mujagic, E.

    2010-01-01

    Quantum cascade lasers (QCLs) are electrically driven semiconductor lasers, which have undergone a steady improvement since the first demonstration in 1994. These are now well established as reliable sources of coherent light in the mid-infrared (MIR) and terahertz (THz)range of the electromagnetic spectrum (3-300 μm). The rapid progress of this type of lasers is based on a high degree of freedom in tailoring the emission wavelength within a large variety of semiconductor heterostructure designs and materials. These properties have attracted the attention of various applications such as gas analysis, chemical sensing, spectral imaging and free-space telecommunication. In order to improve the selectivity, sensitivity and efficiency of today's sensor systems, high optical power, continuous wave and room temperature performance, single-mode operation and low divergence optical beams, are highly desirable qualities of a compact laser source in this field of research. Since all of these features cannot be provided by a conventional edge-emitting device at the same time, research has put focus on the development of surface emitting devices. Nowadays, the vertical cavity surface emitting lasers (VCSELs) are the most prominent representative for this type of light emitters. With its capability of producing narrow circular beams, the feasibility of two-dimensional arrays and on-wafer testing, such a coherent light source results in a reduction of the fabrication effort and production costs. Since the radiation in QCLs is strictly polarized normal to the epitaxial layer plane, fabrication of VCSELs based on QC structures is not viable. The subject of this work is the design and realization of 'ring cavity surface emitting lasers' (ring-CSELs). This type of lasers employs a circular ring cavity and a resonant distributed feedback (DFB) surface grating. Ring-CSELs were fabricated on the basis of MIR and THz QC structures, which cover a wavelength range from 4 μm to 93

  9. Key techniques for space-based solar pumped semiconductor lasers

    Science.gov (United States)

    He, Yang; Xiong, Sheng-jun; Liu, Xiao-long; Han, Wei-hua

    2014-12-01

    In space, the absence of atmospheric turbulence, absorption, dispersion and aerosol factors on laser transmission. Therefore, space-based laser has important values in satellite communication, satellite attitude controlling, space debris clearing, and long distance energy transmission, etc. On the other hand, solar energy is a kind of clean and renewable resources, the average intensity of solar irradiation on the earth is 1353W/m2, and it is even higher in space. Therefore, the space-based solar pumped lasers has attracted much research in recent years, most research focuses on solar pumped solid state lasers and solar pumped fiber lasers. The two lasing principle is based on stimulated emission of the rare earth ions such as Nd, Yb, Cr. The rare earth ions absorb light only in narrow bands. This leads to inefficient absorption of the broad-band solar spectrum, and increases the system heating load, which make the system solar to laser power conversion efficiency very low. As a solar pumped semiconductor lasers could absorb all photons with energy greater than the bandgap. Thus, solar pumped semiconductor lasers could have considerably higher efficiencies than other solar pumped lasers. Besides, solar pumped semiconductor lasers has smaller volume chip, simpler structure and better heat dissipation, it can be mounted on a small satellite platform, can compose satellite array, which can greatly improve the output power of the system, and have flexible character. This paper summarizes the research progress of space-based solar pumped semiconductor lasers, analyses of the key technologies based on several application areas, including the processing of semiconductor chip, the design of small and efficient solar condenser, and the cooling system of lasers, etc. We conclude that the solar pumped vertical cavity surface-emitting semiconductor lasers will have a wide application prospects in the space.

  10. Thermoreflectance spectroscopy—Analysis of thermal processes in semiconductor lasers

    Science.gov (United States)

    Pierścińska, D.

    2018-01-01

    This review focuses on theoretical foundations, experimental implementation and an overview of experimental results of the thermoreflectance spectroscopy as a powerful technique for temperature monitoring and analysis of thermal processes in semiconductor lasers. This is an optical, non-contact, high spatial resolution technique providing high temperature resolution and mapping capabilities. Thermoreflectance is a thermometric technique based on measuring of relative change of reflectivity of the surface of laser facet, which provides thermal images useful in hot spot detection and reliability studies. In this paper, principles and experimental implementation of the technique as a thermography tool is discussed. Some exemplary applications of TR to various types of lasers are presented, proving that thermoreflectance technique provides new insight into heat management problems in semiconductor lasers and in particular, that it allows studying thermal degradation processes occurring at laser facets. Additionally, thermal processes and basic mechanisms of degradation of the semiconductor laser are discussed.

  11. High Power Mid-IR Semiconductor Lasers for LADAR

    National Research Council Canada - National Science Library

    Lester, Luke

    2003-01-01

    The growing need for antimonide-based, room temperature, 2-5 micrometers, semiconductor lasers for trace gas spectroscopy, ultra-low loss communication, infrared countermeasures, and ladar motivated this work...

  12. Theoretical and experimental study of stochastic effects on polarization rotation in a vectorial bistable laser

    International Nuclear Information System (INIS)

    Singh, Kamal P.; Ropars, Guy; Brunel, Marc; Le Floch, Albert

    2006-01-01

    We investigate the two-dimensional optical rotor of a weakly modulated vectorial bistable laser submitted to a single or multiple stochastic perturbations. In the Langevin-type equation of the rotor the role of an even or odd input forcing function on the system dynamics is isolated. Through these two inputs of optical and magnetic natures we verify that the stochastic resonance exists only when the periodic modulation acts on the even parity optical input. When two mutually correlated noises are simultaneously submitted to the input functions of opposite parities, we find a critical regime of the noise interplay whereby one stable state becomes noise-free. In this case, the residence time of the light vector in the noise-free state diverges which leads to a collapse of the output signal-to-noise ratio. But, in this critical regime also obtained when one noise drives both the even and odd functions, if the system symmetry is broken through an independent lever control, we can recover the switching cycle due to a new response mechanism, namely, the dual stochastic response, with a specific output signal-to-noise ratio expression. Both the theoretical analysis and the experiment show that the signal-to-noise ratio now displays a robust behavior for a large range of the input noise amplitude, and a plateau with respect to the input signal amplitude. Furthermore, we isolate an original signature of this synchronization mechanism in the residence-time distribution leading to a broadband forcing frequency range. These noise interplay effects in a double well potential are of generic nature and could be found in other nonlinear systems

  13. Quantum confined laser devices optical gain and recombination in semiconductors

    CERN Document Server

    Blood, Peter

    2015-01-01

    The semiconductor laser, invented over 50 years ago, has had an enormous impact on the digital technologies that now dominate so many applications in business, commerce and the home. The laser is used in all types of optical fibre communication networks that enable the operation of the internet, e-mail, voice and skype transmission. Approximately one billion are produced each year for a market valued at around $5 billion. Nearly all semiconductor lasers now use extremely thin layers of light emitting materials (quantum well lasers). Increasingly smaller nanostructures are used in the form of quantum dots. The impact of the semiconductor laser is surprising in the light of the complexity of the physical processes that determine the operation of every device. This text takes the reader from the fundamental optical gain and carrier recombination processes in quantum wells and quantum dots, through descriptions of common device structures to an understanding of their operating characteristics. It has a consistent...

  14. Hybrid organic semiconductor lasers for bio-molecular sensing.

    Science.gov (United States)

    Haughey, Anne-Marie; Foucher, Caroline; Guilhabert, Benoit; Kanibolotsky, Alexander L; Skabara, Peter J; Burley, Glenn; Dawson, Martin D; Laurand, Nicolas

    2014-01-01

    Bio-functionalised luminescent organic semiconductors are attractive for biophotonics because they can act as efficient laser materials while simultaneously interacting with molecules. In this paper, we present and discuss a laser biosensor platform that utilises a gain layer made of such an organic semiconductor material. The simple structure of the sensor and its operation principle are described. Nanolayer detection is shown experimentally and analysed theoretically in order to assess the potential and the limits of the biosensor. The advantage conferred by the organic semiconductor is explained, and comparisons to laser sensors using alternative dye-doped materials are made. Specific biomolecular sensing is demonstrated, and routes to functionalisation with nucleic acid probes, and future developments opened up by this achievement, are highlighted. Finally, attractive formats for sensing applications are mentioned, as well as colloidal quantum dots, which in the future could be used in conjunction with organic semiconductors.

  15. Optical bistability controlling light with light

    CERN Document Server

    Gibbs, Hyatt

    1985-01-01

    Optical Bistability: Controlling Light with Light focuses on optical bistability in nonlinear optical systems. Emphasis is on passive (non-laser) systems that exhibit reversible bistability with input intensity as the hysteresis variable, along with the physics and the potential applications of such systems for nonlinear optical signal processing. This book consists of seven chapters and begins with a historical overview of optical bistability in lasers and passive systems. The next chapter describes steady-state theories of optical bistability, including the Bonifacio-Lugiato model, as we

  16. Synchronization scenario of two distant mutually coupled semiconductor lasers

    DEFF Research Database (Denmark)

    Mulet, Josep; Mirasso, Claudio; Heil, Tilmann

    2004-01-01

    We present numerical and experimental investigations of the synchronization of the coupling-induced instabilities in two distant mutually coupled semiconductor lasers. In our experiments, two similar Fabry-Perot lasers are coupled via their coherent optical fields. Our theoretical framework is ba...

  17. Driver circuit for pulse modulation of a semiconductor laser

    International Nuclear Information System (INIS)

    Ueki, A.

    1975-01-01

    A pulse modulation driver circuit for a semiconductor laser is disclosed which discriminates among input pulse signals composed of binary codes to detect the occurrence of a pulse having a code of ''I'' following a pulse having a code of ''0''. Detection of this pattern is used to control the driver to increase either or both the width or peak value of the pulse having a code of 1. The effect of this is to eliminate a pattern effect in the light emitted by the semiconductor laser caused by an attenuation of the population inversion in the laser. (U.S.)

  18. Direct solar pumping of semiconductor lasers: A feasibility study

    Science.gov (United States)

    Anderson, Neal G.

    1992-01-01

    This report describes results of NASA Grant NAG-1-1148, entitled Direct Solar Pumping of Semiconductor Lasers: A Feasibility Study. The goals of this study were to provide a preliminary assessment of the feasibility of pumping semiconductor lasers in space with directly focused sunlight and to identify semiconductor laser structures expected to operate at the lowest possible focusing intensities. It should be emphasized that the structures under consideration would provide direct optical-to-optical conversion of sunlight into laser light in a single crystal, in contrast to a configuration consisting of a solar cell or storage battery electrically pumping a current injection laser. With external modulation, such lasers could perhaps be efficient sources for intersatellite communications. We proposed specifically to develop a theoretical model of semiconductor quantum-well lasers photopumped by a broadband source, test it against existing experimental data where possible, and apply it to estimating solar pumping requirements and identifying optimum structures for operation at low pump intensities. These tasks have been accomplished, as described in this report of our completed project. The report is organized as follows: Some general considerations relevant to the solar-pumped semiconductor laser problem are discussed in Section 2, and the types of structures chosen for specific investigation are described. The details of the laser model we developed for this work are then outlined in Section 3. In Section 4, results of our study are presented, including designs for optimum lattice-matched and strained-layer solar-pumped quantum-well lasers and threshold pumping estimates for these structures. It was hoped at the outset of this work that structures could be identified which could be expected to operate continuously at solar photoexcitation intensities of several thousand suns, and this indeed turned out to be the case as described in this section. Our project is

  19. Semiconductor Laser Multi-Spectral Sensing and Imaging

    Directory of Open Access Journals (Sweden)

    Han Q. Le

    2010-01-01

    Full Text Available Multi-spectral laser imaging is a technique that can offer a combination of the laser capability of accurate spectral sensing with the desirable features of passive multispectral imaging. The technique can be used for detection, discrimination, and identification of objects by their spectral signature. This article describes and reviews the development and evaluation of semiconductor multi-spectral laser imaging systems. Although the method is certainly not specific to any laser technology, the use of semiconductor lasers is significant with respect to practicality and affordability. More relevantly, semiconductor lasers have their own characteristics; they offer excellent wavelength diversity but usually with modest power. Thus, system design and engineering issues are analyzed for approaches and trade-offs that can make the best use of semiconductor laser capabilities in multispectral imaging. A few systems were developed and the technique was tested and evaluated on a variety of natural and man-made objects. It was shown capable of high spectral resolution imaging which, unlike non-imaging point sensing, allows detecting and discriminating objects of interest even without a priori spectroscopic knowledge of the targets. Examples include material and chemical discrimination. It was also shown capable of dealing with the complexity of interpreting diffuse scattered spectral images and produced results that could otherwise be ambiguous with conventional imaging. Examples with glucose and spectral imaging of drug pills were discussed. Lastly, the technique was shown with conventional laser spectroscopy such as wavelength modulation spectroscopy to image a gas (CO. These results suggest the versatility and power of multi-spectral laser imaging, which can be practical with the use of semiconductor lasers.

  20. Semiconductor laser multi-spectral sensing and imaging.

    Science.gov (United States)

    Le, Han Q; Wang, Yang

    2010-01-01

    Multi-spectral laser imaging is a technique that can offer a combination of the laser capability of accurate spectral sensing with the desirable features of passive multispectral imaging. The technique can be used for detection, discrimination, and identification of objects by their spectral signature. This article describes and reviews the development and evaluation of semiconductor multi-spectral laser imaging systems. Although the method is certainly not specific to any laser technology, the use of semiconductor lasers is significant with respect to practicality and affordability. More relevantly, semiconductor lasers have their own characteristics; they offer excellent wavelength diversity but usually with modest power. Thus, system design and engineering issues are analyzed for approaches and trade-offs that can make the best use of semiconductor laser capabilities in multispectral imaging. A few systems were developed and the technique was tested and evaluated on a variety of natural and man-made objects. It was shown capable of high spectral resolution imaging which, unlike non-imaging point sensing, allows detecting and discriminating objects of interest even without a priori spectroscopic knowledge of the targets. Examples include material and chemical discrimination. It was also shown capable of dealing with the complexity of interpreting diffuse scattered spectral images and produced results that could otherwise be ambiguous with conventional imaging. Examples with glucose and spectral imaging of drug pills were discussed. Lastly, the technique was shown with conventional laser spectroscopy such as wavelength modulation spectroscopy to image a gas (CO). These results suggest the versatility and power of multi-spectral laser imaging, which can be practical with the use of semiconductor lasers.

  1. Development of the power control system for semiconductor lasers

    International Nuclear Information System (INIS)

    Kim, Kwang Suk; Kim, Cheol Jung

    1997-12-01

    For the first year plan of this program, we developed the power control system for semiconductor lasers. We applied the high-current switching mode techniques to fabricating a power control system. Then, we investigated the direct side pumping techniques with GaA1As diode laser bars to laser crystal without pumping optics. We obtained 0.5W average output power from this DPSSL. (author). 54 refs., 3 tabs., 18 figs

  2. Semiconductor quantum-dot lasers and amplifiers

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher; Borri, Paola; Ledentsov, N. N.

    2002-01-01

    -power surface emitting VCSELs. We investigated the ultrafast dynamics of quantum-dot semiconductor optical amplifiers. The dephasing time at room temperature of the ground-state transition in semiconductor quantum dots is around 250 fs in an unbiased amplifier, decreasing to below 50 fs when the amplifier...... is biased to positive net gain. We have further measured gain recovery times in quantum dot amplifiers that are significantly lower than in bulk and quantum-well semiconductor optical amplifiers. This is promising for future demonstration of quantum dot devices with high modulation bandwidth...

  3. Laser apparatus for surgery and force therapy based on high-power semiconductor and fibre lasers

    International Nuclear Information System (INIS)

    Minaev, V P

    2005-01-01

    High-power semiconductor lasers and diode-pumped lasers are considered whose development qualitatively improved the characteristics of laser apparatus for surgery and force therapy, extended the scope of their applications in clinical practice, and enhanced the efficiency of medical treatment based on the use of these lasers. The characteristics of domestic apparatus are presented and their properties related to the laser emission wavelength used in them are discussed. Examples of modern medical technologies based on these lasers are considered. (invited paper)

  4. Construction of an optical semiconductor amplifier starting from a Fabry-Perot semiconductor laser

    International Nuclear Information System (INIS)

    Garcia, E.; Soto, H.; Marquez, H.; Valles V, N.

    2000-01-01

    A methodology to convert a semiconductor laser Fabry-Perot (SL-FP) in a semiconductor optical amplifier (SOA) is presented. In order to suppress the cavity resonant an optical thin film coating was deposited on the facets of the SL-FP. The experiment was carried out putting on service a new monitoring technique that consist in the observation of the laser power spectrum during the antireflection coatings deposition. This allows to determine the moment were the facets reflectivity is minimum. The SOA obtained was characterized for different polarization currents. (Author)

  5. Heteroclinic dynamics of coupled semiconductor lasers with optoelectronic feedback.

    Science.gov (United States)

    Shahin, S; Vallini, F; Monifi, F; Rabinovich, M; Fainman, Y

    2016-11-15

    Generalized Lotka-Volterra (GLV) equations are important equations used in various areas of science to describe competitive dynamics among a population of N interacting nodes in a network topology. In this Letter, we introduce a photonic network consisting of three optoelectronically cross-coupled semiconductor lasers to realize a GLV model. In such a network, the interaction of intensity and carrier inversion rates, as well as phases of laser oscillator nodes, result in various dynamics. We study the influence of asymmetric coupling strength and frequency detuning between semiconductor lasers and show that inhibitory asymmetric coupling is required to achieve consecutive amplitude oscillations of the laser nodes. These studies were motivated primarily by the dynamical models used to model brain cognitive activities and their correspondence with dynamics obtained among coupled laser oscillators.

  6. Gain and Index Dynamics in Semiconductor Lasers

    DEFF Research Database (Denmark)

    Hvam, Jørn Märcher

    Semiconductor optical amplifiers (SOAs) provide ultrafast, i.e. broadband components for optical communication systems. They enter not only as signal generators and amplifiers, but also as nonlinear elements for ultrafast signal processing such as wavelength conversion, switching, and regeneration...... changed character from bulk semiconductor to quantum wells and most recently to quantum dots. By quantum confinement of the carriers, the light-matter interactions can be significantly modified and the optical properties, including dynamics, can be engineered to match the required functionalities...

  7. Ultrafast dynamics and laser action of organic semiconductors

    CERN Document Server

    Vardeny, Zeev Valy

    2009-01-01

    Spurred on by extensive research in recent years, organic semiconductors are now used in an array of areas, such as organic light emitting diodes (OLEDs), photovoltaics, and other optoelectronics. In all of these novel applications, the photoexcitations in organic semiconductors play a vital role. Exploring the early stages of photoexcitations that follow photon absorption, Ultrafast Dynamics and Laser Action of Organic Semiconductors presents the latest research investigations on photoexcitation ultrafast dynamics and laser action in pi-conjugated polymer films, solutions, and microcavities.In the first few chapters, the book examines the interplay of charge (polarons) and neutral (excitons) photoexcitations in pi-conjugated polymers, oligomers, and molecular crystals in the time domain of 100 fs-2 ns. Summarizing the state of the art in lasing, the final chapters introduce the phenomenon of laser action in organics and cover the latest optoelectronic applications that use lasing based on a variety of caviti...

  8. Return-map for semiconductor lasers with optical feedback

    DEFF Research Database (Denmark)

    Mørk, Jesper; Tromborg, Bjarne; Sabbatier, H.

    1999-01-01

    It is well known that a semiconductor laser exposed to moderate optical feedback and biased near threshold exhibits the phenomenon of low-frequency intensity fluctuations (LFF). While this behavior can be numerically simulated using the so-called Lang-Kobayshi model, the interpretation of the phe......It is well known that a semiconductor laser exposed to moderate optical feedback and biased near threshold exhibits the phenomenon of low-frequency intensity fluctuations (LFF). While this behavior can be numerically simulated using the so-called Lang-Kobayshi model, the interpretation...

  9. Optically pumped semiconductor lasers for atomic and molecular physics

    Science.gov (United States)

    Burd, S.; Leibfried, D.; Wilson, A. C.; Wineland, D. J.

    2015-03-01

    Experiments in atomic, molecular and optical (AMO) physics rely on lasers at many different wavelengths and with varying requirements on spectral linewidth, power and intensity stability. Optically pumped semiconductor lasers (OPSLs), when combined with nonlinear frequency conversion, can potentially replace many of the laser systems currently in use. We are developing a source for laser cooling and spectroscopy of Mg+ ions at 280 nm, based on a frequency quadrupled OPSL with the gain chip fabricated at the ORC at Tampere Univ. of Technology, Finland. This OPSL system could serve as a prototype for many other sources used in atomic and molecular physics.

  10. Integrated semiconductor twin-microdisk laser under mutually optical injection

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Ling-Xiu; Liu, Bo-Wen; Lv, Xiao-Meng; Yang, Yue-De; Xiao, Jin-Long; Huang, Yong-Zhen, E-mail: yzhuang@semi.ac.cn [State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China)

    2015-05-11

    We experimentally study the characteristics of an integrated semiconductor twin-microdisk laser under mutually optical injection through a connected optical waveguide. Based on the lasing spectra, four-wave mixing, injection locking, and period-two oscillation states are observed due to the mutually optical injection by adjusting the injected currents applied to the two microdisks. The enhanced 3 dB bandwidth is realized for the microdisk laser at the injection locking state, and photonic microwave is obtained from the electrode of the microdisk laser under the period-two oscillation state. The plentifully dynamical states similar as semiconductor lasers subject to external optical injection are realized due to strong optical interaction between the two microdisks.

  11. Management of gingival hyperpigmentation by semiconductor diode laser

    Directory of Open Access Journals (Sweden)

    Geeti Gupta

    2011-01-01

    Full Text Available Gingival hyperpigmentation is caused by excessive deposition of melanin in the basal and suprabasal cell layers of the epithelium. Although melanin pigmentation of the gingiva is completely benign, cosmetic concerns are common, particularly in patients having a very high smile line (gummy smile. Various depigmentation techniques have been employed, such as scalpel surgery, gingivectomy, gingivectomy with free gingival autografting, cryosurgery, electrosurgery, chemical agents such as 90% phenol and 95% alcohol, abrasion with diamond burs, Nd:YAG laser, semiconductor diode laser, and CO 2 laser. The present case report describes simple and effective depigmentation technique using semiconductor diode laser surgery - for gingival depigmentation, which have produced good results with patient satisfaction.

  12. Low-confinement high-power semiconductor lasers

    NARCIS (Netherlands)

    Buda, M.

    1999-01-01

    This thesis presents the results of studies related to optimisation of high power semiconductor laser diodes using the low confinement concept. This implies a different approach in designing the transversal layer structure before growth and in processing the wafer after growth, for providing the

  13. Optical trapping with Bessel beams generated from semiconductor lasers

    International Nuclear Information System (INIS)

    Sokolovskii, G S; Dudelev, V V; Losev, S N; Soboleva, K K; Deryagin, A G; Kuchinskii, V I; Sibbett, W; Rafailov, E U

    2014-01-01

    In this paper, we study generation of Bessel beams from semiconductor lasers with high beam propagation parameter M 2 and their utilization for optical trapping and manipulation of microscopic particles including living cells. The demonstrated optical tweezing with diodegenerated Bessel beams paves the way to replace their vibronic-generated counterparts for a range of applications towards novel lab-on-a-chip configurations

  14. Semiconductor Mode-Locked Lasers for Optical Communication Systems

    DEFF Research Database (Denmark)

    Yvind, Kresten

    2003-01-01

    The thesis deals with the design and fabrication of semiconductor mode-locked lasers for use in optical communication systems. The properties of pulse sources and characterization methods are described as well as requirements for application in communication systems. Especially, the importance of...

  15. Dynamics of laterally coupled semiconductor lasers: transition to chaos

    NARCIS (Netherlands)

    Yousefi, M.; Barsella, A.; Lenstra, D.; Lenstra, D.; Morthier, G.; Erneux, T.; Pessa, M.

    2004-01-01

    A method for the investigation of the dynamics of two semiconductor lasers, grown side-by-side on the same wafer to enhance the lateral optical coupling, is presented. Using steady state analysis, parameter regimes of relevant dynamics are identified. This is completed by a spectral analysis, were

  16. Material Engineering for Monolithic Semiconductor Mode-Locked Lasers

    DEFF Research Database (Denmark)

    Kulkova, Irina

    This thesis is devoted to the materials engineering for semiconductor monolithic passively mode-locked lasers (MLLs) as a compact energy-efficient source of ultrashort optical pulses. Up to the present day, the achievement of low-noise sub-picosecond pulse generation has remained a challenge...

  17. Mathematical modeling of thermal runaway in semiconductor laser operation

    NARCIS (Netherlands)

    Smith, W.R.

    2000-01-01

    A mathematical model describing the coupling of electrical, optical and thermal effects in semiconductor lasers is introduced. Through a systematic asymptotic expansion, the governing system of differential equations is reduced to a single second-order boundary value problem. This highly nonlinear

  18. Absolute Distance Measurements with Tunable Semiconductor Laser

    Czech Academy of Sciences Publication Activity Database

    Mikel, Břetislav; Číp, Ondřej; Lazar, Josef

    T118, - (2005), s. 41-44 ISSN 0031-8949 R&D Projects: GA AV ČR(CZ) IAB2065001 Keywords : tunable laser * absolute interferometer Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.661, year: 2004

  19. Electrically pumped edge-emitting photonic bandgap semiconductor laser

    Science.gov (United States)

    Lin, Shawn-Yu; Zubrzycki, Walter J.

    2004-01-06

    A highly efficient, electrically pumped edge-emitting semiconductor laser based on a one- or two-dimensional photonic bandgap (PBG) structure is described. The laser optical cavity is formed using a pair of PBG mirrors operating in the photonic band gap regime. Transverse confinement is achieved by surrounding an active semiconductor layer of high refractive index with lower-index cladding layers. The cladding layers can be electrically insulating in the passive PBG mirror and waveguide regions with a small conducting aperture for efficient channeling of the injection pump current into the active region. The active layer can comprise a quantum well structure. The quantum well structure can be relaxed in the passive regions to provide efficient extraction of laser light from the active region.

  20. Radiation effects in semiconductor laser diode arrays

    International Nuclear Information System (INIS)

    Carson, R.F.

    1988-01-01

    The effects of radiation events are important for many of the present and future applications that involve optoelectronic components. Laser diodes show a strong resistance to degradation by gamma rays, prompt x-rays and (to a lesser extent), neutrons. This is due to the short carrier lifetime that is associated with stimulated emission and the high current injection conditions that are present in these devices. Radiation-resistant properties should carry over to many of the more recently developed devices such as multi-stripe array and broad area laser diodes. There are, however, additional considerations for radiation tolerance that are introduced by these devices. Arrays and other high power laser diodes have larger active region volumes than lower power single stripe devices. In addition, evanescent field coupling between stripes, the material quality available from newer MOCVD epitaxial growth techniques, and stripe definition methods may all influence the radiation tolerance of the high power laser diode devices. Radiation tests have been conducted on various GaAs-GaAlAs laser diode array and broad area devices. Tests involving total gamma dose have indicated that high power laser diodes and arrays have small degradations in light power output with current input after 4 MRad(Si) of radiation from a Co 60 source. Additional test results involving flash x-rays indicate that high power diode lasers and arrays are tolerant to 10 12 rads(Si)/sec, when observed on microsecond or millisecond time scales. High power diode laser devices were also irradiated with neutrons to a fluence of 10 14 neutrons/cm 2 with some degradation of threshold current level

  1. A proposal for Coulomb assisted laser cooling of piezoelectric semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Nia, Iman Hassani; Mohseni, Hooman, E-mail: hmohseni@ece.northwestern.edu [Bio-Inspired Sensors and Optoelectronics Laboratory (BISOL), Department of Electrical Engineering, Northwestern University, Evanston, Illinois 60208 (United States)

    2014-07-28

    Anti-Stokes laser cooling of semiconductors as a compact and vibration-free method is very attractive. While it has achieved significant milestones, increasing its efficiency is highly desirable. The main limitation is the lack of the pristine material quality with high luminescence efficiency. Here, we theoretically demonstrate that the Coulomb interaction among electrons and holes in piezoelectric heterostructures could lead to coherent damping of acoustic phonons; rendering a significantly higher efficiency that leads to the possibility of cooling a broad range of semiconductors.

  2. High-Speed and Low-Energy Flip-Flop Operation of Asymmetric Active-Multimode Interferometer Bi-Stable Laser Diodes

    DEFF Research Database (Denmark)

    Jiang, Haisong; Chaen, Yutaka; Hagio, Takuma

    2011-01-01

    High-speed (121/25 ps rise/fall time) and low-switching energy (7.1 and 3.4 fJ) alloptical flip-flop operation of single-wavelength high-mesa asymmetric active-MMI bi-stable laser diodes is demonstrated for the first time using 25 ps long switching pulses.......High-speed (121/25 ps rise/fall time) and low-switching energy (7.1 and 3.4 fJ) alloptical flip-flop operation of single-wavelength high-mesa asymmetric active-MMI bi-stable laser diodes is demonstrated for the first time using 25 ps long switching pulses....

  3. The history of laser conditions in semiconductors

    International Nuclear Information System (INIS)

    Bernard, Maurice

    2012-01-01

    Fifty years ago, summer 1962: in three independent laboratories of the US East Coast, almost simultaneously, IR coherent light was for the first time emitted from semiconductor crystals. No theory was associated with these results. Two years before, Georges Duraffourg and Maurice Bernard had readily proved that for such phenomenon to occur requires that a relation is fulfilled between quasi-Fermi levels and photon energy: F n − F p > hν. This paper presents an overview of this important period of history and the events that occurred around that time. (paper)

  4. Singly-resonant sum frequency generation of visible light in a semiconductor disk laser

    DEFF Research Database (Denmark)

    Andersen, Martin Thalbitzer; Schlosser, P.J.; Hastie, J.E.

    2009-01-01

    In this paper a generic approach for visible light generation is presented. It is based on sum frequency generation between a semiconductor disk laser and a solid-state laser, where the frequency mixing is achieved within the cavity of the semiconductor disk laser using a singlepass of the solid......-state laser light. This exploits the good beam quality and high intra-cavity power present in the semiconductor disk laser to achieve high conversion efficiency. Combining sum frequency mixing and semiconductor disk lasers in this manner allows in principle for generation of any wavelength within the visible...

  5. Design and Characterisation of III-V Semiconductor Nanowire Lasers

    Science.gov (United States)

    Saxena, Dhruv

    The development of small, power-efficient lasers underpins many of the technologies that we utilise today. Semiconductor nanowires are promising for miniaturising lasers to even smaller dimensions. III-V semiconductors, such as Gallium Arsenide (GaAs) and Indium Phosphide (InP), are the most widely used materials for optoelectronic devices and so the development of nanowire lasers based on these materials is expected to have technologically significant outcomes. This PhD dissertation presents a comprehensive study of the design of III-V semiconductor nanowire lasers, with bulk and quantum confined active regions. Based on the design, various III-V semiconductor nanowire lasers are demonstrated, namely, GaAs nanowire lasers, GaAs/AlGaAs multi-quantum well (MQW) nanowire lasers and InP nanowire lasers. These nanowire lasers are shown to operate at room temperature, have low thresholds, and lase from different transverse modes. The structural and optoelectronic quality of nanowire lasers are characterised via electron microscopy and photoluminescence spectroscopic techniques. Lasing is characterised in all these devices by optical pumping. The lasing characteristics are analysed by rate equation modelling and the lasing mode(s) in these devices is characterised by threshold gain modelling, polarisation measurements and Fourier plane imaging. Firstly, GaAs nanowire lasers that operate at room temperature are demonstrated. This is achieved by determining the optimal nanowire diameter to reduce threshold gain and by passivating nanowires to improve their quantum efficiency (QE). High-quality surface passivated GaAs nanowires of suitable diameters are grown. The growth procedure is tailored to improve both QE and structural uniformity of nanowires. Room-temperature lasing is demonstrated from individual nanowires and lasing is characterised to be from TM01 mode by threshold gain modelling. To lower threshold even further, nanowire lasers with GaAs/AlGaAs coaxial multi

  6. Review on the dynamics of semiconductor nanowire lasers

    Science.gov (United States)

    Röder, Robert; Ronning, Carsten

    2018-03-01

    Semiconductor optoelectronic devices have contributed tremendously to the technological progress in the past 50-60 years. Today, they also play a key role in nanophotonics stimulated by the inherent limitations of electronic integrated circuits and the growing demand for faster communications on chip. In particular, the field of ‘nanowire photonics’ has emerged including the search for coherent light sources with a nano-scaled footprint. The past decade has been dedicated to find suitable semiconductor nanowire (NW) materials for such nanolasers. Nowadays, such NW lasers consistently work at room temperature covering a huge spectral range from the ultraviolet down to the mid-infrared depending on the band gap of the NW material. Furthermore, first approaches towards the modification and optimization of such NW laser devices have been demonstrated. The underlying dynamics of the electronic and photonic NW systems have also been studied very recently, as they need to be understood in order to push the technological relevance of nano-scaled coherent light sources. Therefore, this review will first present novel measurement approaches in order to study the ultrafast temporal and optical mode dynamics of individual NW laser devices. Furthermore, these fundamental new insights are reviewed and deeply discussed towards the efficient control and adjustment of the dynamics in semiconductor NW lasers.

  7. Synchronous characterization of semiconductor microcavity laser beam.

    Science.gov (United States)

    Wang, T; Lippi, G L

    2015-06-01

    We report on a high-resolution double-channel imaging method used to synchronously map the intensity- and optical-frequency-distribution of a laser beam in the plane orthogonal to the propagation direction. The synchronous measurement allows us to show that the laser frequency is an inhomogeneous distribution below threshold, but that it becomes homogeneous across the fundamental Gaussian mode above threshold. The beam's tails deviations from the Gaussian shape, however, are accompanied by sizeable fluctuations in the laser wavelength, possibly deriving from manufacturing details and from the influence of spontaneous emission in the very low intensity wings. In addition to the synchronous spatial characterization, a temporal analysis at any given point in the beam cross section is carried out. Using this method, the beam homogeneity and spatial shape, energy density, energy center, and the defects-related spectrum can also be extracted from these high-resolution pictures.

  8. Monolithic integration of a resonant tunneling diode and a quantum well semiconductor laser

    Science.gov (United States)

    Grave, I.; Kan, S. C.; Griffel, G.; Wu, S. W.; Sa'Ar, A.

    1991-01-01

    A monolithic integration of a double barrier AlAs/GaAs resonant tunneling diode and a GaAs/AlGaAs quantum well laser is reported. Negative differential resistance and negative differential optical response are observed at room temperature. The device displays bistable electrical and optical characteristics which are voltage controlled. Operation as a two-state optical memory is demonstrated.

  9. Semiconductor Laser Wind Lidar for Turbine Control

    DEFF Research Database (Denmark)

    Hu, Qi

    This thesis describes an experimentally oriented study of continuous wave (CW) coherent Doppler lidar system design. The main application is remote wind sensing for active wind turbine control using nacelle mounted lidar systems; and the primary focus is to devise an industrial instrument that can...... historical overview within the topic of wind lidar systems. Both the potential and the challenges of an industrialized wind lidar has been addressed here. Furthermore, the basic concept behind the heterodyne detection and a brief overview of the lidar signal processing is explained; and a simple...... investigation of the telescope truncation and lens aberrations is conducted, both numerically and experimentally. It is shown that these parameters dictate the spatial resolution of the lidar system, and have profound impact on the SNR. In this work, an all-semiconductor light source is used in the lidar design...

  10. On increasing the efficiency of a streamer semiconductor laser

    International Nuclear Information System (INIS)

    Rusakov, K I; Parashchuk, V V

    2007-01-01

    The influence of intense electric and optical fields produced by a streamer discharge in wide-gap semiconductors on their spectroscopic properties is studied. The effect is manifested in the reversible change of the luminescence parameters of the active medium. Methods are proposed for increasing the service life and efficiency of a streamer laser in limiting regimes, which are based on the use of semiconductor protective layers of a certain crystallographic orientation and a crystal microrelief with the size of elements of the order of the wavelength of light. Streamer emission was observed and studied in new promising Eu:CaGa 2 S 4 and Eu:Ca 4 Ga 2 S 7 materials. (lasers)

  11. Final Report: High Power Semiconductor Laser Sources,

    Science.gov (United States)

    1989-01-01

    Mittelstein, Yasuhiko Arakawa, ) Anders Larssonb) and Amnon Yariv California Institute of Technology, Pasadena, California 91 125~412 (Received 7 July...Electronics and Commu- nication Engineers of Japan. He is a member of the Institute of Electronics Yasuhiko Arakawa S󈨑-M󈨔) was born in Ai- and...Gain, Modulation Response, and Spectral Linewidth in AlGaAs Quantum Well Lasers YASUHIKO ARAKAWA. MEMBER, IEEE. AND AMNON YARIV. FELLOW. IEEE Abstract

  12. Nonlinear gain suppression in semiconductor lasers due to carrier heating

    International Nuclear Information System (INIS)

    Willatzen, M.; Uskov, A.; Moerk, J.; Olesen, H.; Tromborg, B.; Jauho, A.P.

    1991-01-01

    We present a simple model for carrier heating in semiconductor lasers, from which the temperature dynamics of the electron and hole distributions can be calculated. Analytical expressions for two new contributions to the nonlinear gain coefficient ε are derived, which reflect carrier heating due to stimulated emission and free carrier absorption. In typical cases, carrier heating and spectral holeburning are found to give comparable contributions to nonlinear gain suppression. The results are in good agreement with recent measurements on InGaAsP laser diodes. (orig.)

  13. Semiconductor ring lasers coupled by a single waveguide

    Science.gov (United States)

    Coomans, W.; Gelens, L.; Van der Sande, G.; Mezosi, G.; Sorel, M.; Danckaert, J.; Verschaffelt, G.

    2012-06-01

    We experimentally and theoretically study the characteristics of semiconductor ring lasers bidirectionally coupled by a single bus waveguide. This configuration has, e.g., been suggested for use as an optical memory and as an optical neural network motif. The main results are that the coupling can destabilize the state in which both rings lase in the same direction, and it brings to life a state with equal powers at both outputs. These are both undesirable for optical memory operation. Although the coupling between the rings is bidirectional, the destabilization occurs due to behavior similar to an optically injected laser system.

  14. Field-glass range finder with a semiconductor laser

    Science.gov (United States)

    Iwanejko, Leszek; Jankiewicz, Zdzislaw; Jarocki, Roman; Marczak, Jan

    1995-03-01

    This paper presents the project of a laboratory model of a field-glasses range-finger. The optical transmitter of the device contains a commercial pulse semiconductor laser which generates IR wavelength around 905 nm. Some of the technical parameters of this device are: a maximum range of up to 3 km; an accuracy of +/- 5 m, divergence of a laser beam of 1 mrad; a repetition rate of 1 kHz. Dichroic elements of the receiver ensure a capability of an optimization of a field of view, without the worsening of luminance and size of an observation field.

  15. Modes in light wave propagating in semiconductor laser

    Science.gov (United States)

    Manko, Margarita A.

    1994-01-01

    The study of semiconductor laser based on an analogy of the Schrodinger equation and an equation describing light wave propagation in nonhomogeneous medium is developed. The active region of semiconductor laser is considered as optical waveguide confining the electromagnetic field in the cross-section (x,y) and allowing waveguide propagation along the laser resonator (z). The mode structure is investigated taking into account the transversal and what is the important part of the suggested consideration longitudinal nonhomogeneity of the optical waveguide. It is shown that the Gaussian modes in the case correspond to spatial squeezing and correlation. Spatially squeezed two-mode structure of nonhomogeneous optical waveguide is given explicitly. Distribution of light among the laser discrete modes is presented. Properties of the spatially squeezed two-mode field are described. The analog of Franck-Condon principle for finding the maxima of the distribution function and the analog of Ramsauer effect for control of spatial distribution of laser emission are discussed.

  16. Toward continuous-wave operation of organic semiconductor lasers

    Science.gov (United States)

    Sandanayaka, Atula S. D.; Matsushima, Toshinori; Bencheikh, Fatima; Yoshida, Kou; Inoue, Munetomo; Fujihara, Takashi; Goushi, Kenichi; Ribierre, Jean-Charles; Adachi, Chihaya

    2017-01-01

    The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi–continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold. A simple encapsulation technique greatly reduced the laser-induced thermal degradation and suppressed the ablation of the gain medium otherwise taking place under intense continuous-wave photoexcitation. Overall, this study provides evidence that the development of a continuous-wave organic semiconductor laser technology is possible via the engineering of the gain medium and the device architecture. PMID:28508042

  17. Semiconductor laser diodes and the design of a D.C. powered laser diode drive unit

    OpenAIRE

    Cappuccio, Joseph C., Jr.

    1988-01-01

    Approved for public release; distribution is unlimited This thesis addresses the design, development and operational analysis of a D.C. powered semiconductor laser diode drive unit. A laser diode requires an extremely stable power supply since a picosecond spike of current or power supply switching transient could result in permanent damage. The design offers stability and various features for operational protection of the laser diode. The ability to intensity modulate (analog) and pulse m...

  18. Measurement of the emission spectrum of a semiconductor laser using laser-feedback interferometry.

    Science.gov (United States)

    Keeley, James; Freeman, Joshua; Bertling, Karl; Lim, Yah L; Mohandas, Reshma A; Taimre, Thomas; Li, Lianhe H; Indjin, Dragan; Rakić, Aleksandar D; Linfield, Edmund H; Davies, A Giles; Dean, Paul

    2017-08-03

    The effects of optical feedback (OF) in lasers have been observed since the early days of laser development. While OF can result in undesirable and unpredictable operation in laser systems, it can also cause measurable perturbations to the operating parameters, which can be harnessed for metrological purposes. In this work we exploit this 'self-mixing' effect to infer the emission spectrum of a semiconductor laser using a laser-feedback interferometer, in which the terminal voltage of the laser is used to coherently sample the reinjected field. We demonstrate this approach using a terahertz frequency quantum cascade laser operating in both single- and multiple-longitudinal mode regimes, and are able to resolve spectral features not reliably resolved using traditional Fourier transform spectroscopy. We also investigate quantitatively the frequency perturbation of individual laser modes under OF, and find excellent agreement with predictions of the excess phase equation central to the theory of lasers under OF.

  19. Development of semiconductor laser based Doppler lidars for wind-sensing applications

    DEFF Research Database (Denmark)

    Rodrigo, Peter John; Hu, Qi; Pedersen, Christian

    2015-01-01

    We summarize the progress we have made in the development of semiconductor laser (SL) based Doppler lidar systems for remote wind speed and direction measurements. The SL emitter used in our wind-sensing lidar is an integrated diode laser with a tapered (semiconductor) amplifier. The laser source...

  20. Spherical distribution structure of the semiconductor laser diode stack for pumping

    International Nuclear Information System (INIS)

    Zhao Tianzhuo; Yu Jin; Liu Yang; Zhang Xue; Ma Yunfeng; Fan Zhongwei

    2011-01-01

    A semiconductor laser diode stack is used for pumping and 8 semiconductor laser diode arrays of the stack are put on a sphere, and the output of every bar is specially off-axis compressed to realize high coupling efficiency. The output beam of this semiconductor laser diode stack is shaped by a hollow duct to the laser active medium. The efficiency of the hollow light pipe, which is used for semiconductor laser diode stack coupling, is analyzed by geometric optics and ray tracing. Geometric optics analysis diagnoses the reasons for coupling loss and guides the design of the structure. Ray tracing analyzes the relation between the structural parameters and the output characteristics of this pumping system, and guides parameter optimization. Simulation and analysis results show that putting the semiconductor laser diode arrays on a spherical surface can increase coupling efficiency, reduce the optimum duct length and improve the output energy field distribution. (semiconductor devices)

  1. Delay induced high order locking effects in semiconductor lasers

    Science.gov (United States)

    Kelleher, B.; Wishon, M. J.; Locquet, A.; Goulding, D.; Tykalewicz, B.; Huyet, G.; Viktorov, E. A.

    2017-11-01

    Multiple time scales appear in many nonlinear dynamical systems. Semiconductor lasers, in particular, provide a fertile testing ground for multiple time scale dynamics. For solitary semiconductor lasers, the two fundamental time scales are the cavity repetition rate and the relaxation oscillation frequency which is a characteristic of the field-matter interaction in the cavity. Typically, these two time scales are of very different orders, and mutual resonances do not occur. Optical feedback endows the system with a third time scale: the external cavity repetition rate. This is typically much longer than the device cavity repetition rate and suggests the possibility of resonances with the relaxation oscillations. We show that for lasers with highly damped relaxation oscillations, such resonances can be obtained and lead to spontaneous mode-locking. Two different laser types-—a quantum dot based device and a quantum well based device—are analysed experimentally yielding qualitatively identical dynamics. A rate equation model is also employed showing an excellent agreement with the experimental results.

  2. Transient thermal analysis of semiconductor diode lasers under pulsed operation

    Science.gov (United States)

    Veerabathran, G. K.; Sprengel, S.; Karl, S.; Andrejew, A.; Schmeiduch, H.; Amann, M.-C.

    2017-02-01

    Self-heating in semiconductor lasers is often assumed negligible during pulsed operation, provided the pulses are `short'. However, there is no consensus on the upper limit of pulse width for a given device to avoid-self heating. In this paper, we present an experimental and theoretical analysis of the effect of pulse width on laser characteristics. First, a measurement method is introduced to study thermal transients of edge-emitting lasers during pulsed operation. This method can also be applied to lasers that do not operate in continuous-wave mode. Secondly, an analytical thermal model is presented which is used to fit the experimental data to extract important parameters for thermal analysis. Although commercial numerical tools are available for such transient analyses, this model is more suitable for parameter extraction due to its analytical nature. Thirdly, to validate this approach, it was used to study a GaSb-based inter-band laser and an InP-based quantum cascade laser (QCL). The maximum pulse-width for less than 5% error in the measured threshold currents was determined to be 200 and 25 ns for the GaSb-based laser and QCL, respectively.

  3. Chaos-pass filtering in injection-locked semiconductor lasers

    International Nuclear Information System (INIS)

    Murakami, Atsushi; Shore, K. Alan

    2005-01-01

    Chaos-pass filtering (CPF) of semiconductor lasers has been studied theoretically. CPF is a phenomenon which occurs in laser chaos synchronization by injection locking and is a fundamental technique for the extraction of messages at the receiver laser in chaotic communications systems. We employ a simple theory based on driven damped oscillators to clarify the physical background of CPF. The receiver laser is optically driven by injection from the transmitter laser. We have numerically investigated the response characteristics of the receiver when it is driven by periodic (message) and chaotic (carrier) signals. It is thereby revealed that the response of the receiver laser in the two cases is quite different. For the periodic drive, the receiver exhibits a response depending on the signal frequency, while the chaotic drive provides a frequency-independent synchronous response to the receiver laser. We verify that the periodic and chaotic drives occur independently in the CPF response, and, consequently, CPF can be clearly understood in the difference of the two drives. Message extraction using CPF is also examined, and the validity of our theoretical explanation for the physical mechanism underlying CPF is thus verified

  4. Optical-cell model based on the lasing competition of mode structures with different Q-factors in high-power semiconductor lasers

    Energy Technology Data Exchange (ETDEWEB)

    Podoskin, A. A., E-mail: podoskin@mail.ioffe.ru; Shashkin, I. S.; Slipchenko, S. O.; Pikhtin, N. A.; Tarasov, I. S. [Russian Academy of Sciences, Ioffe Institute (Russian Federation)

    2015-08-15

    A model describing the operation of a completely optical cell, based on the competition of lasing of Fabry-Perot cavity modes and the high-Q closed mode in high-power semiconductor lasers is proposed. Based on rate equations, the conditions of lasing switching between Fabry-Perot modes for ground and excited lasing levels and the closed mode are considered in the case of increasing internal optical loss under conditions of high current pump levels. The optical-cell operation conditions in the mode of a high-power laser radiation switch (reversible mode-structure switching) and in the mode of a memory cell with bistable irreversible lasing switching between mode structures with various Q-factors are considered.

  5. Fast physical random bit generation with chaotic semiconductor lasers

    Science.gov (United States)

    Uchida, Atsushi; Amano, Kazuya; Inoue, Masaki; Hirano, Kunihito; Naito, Sunao; Someya, Hiroyuki; Oowada, Isao; Kurashige, Takayuki; Shiki, Masaru; Yoshimori, Shigeru; Yoshimura, Kazuyuki; Davis, Peter

    2008-12-01

    Random number generators in digital information systems make use of physical entropy sources such as electronic and photonic noise to add unpredictability to deterministically generated pseudo-random sequences. However, there is a large gap between the generation rates achieved with existing physical sources and the high data rates of many computation and communication systems; this is a fundamental weakness of these systems. Here we show that good quality random bit sequences can be generated at very fast bit rates using physical chaos in semiconductor lasers. Streams of bits that pass standard statistical tests for randomness have been generated at rates of up to 1.7 Gbps by sampling the fluctuating optical output of two chaotic lasers. This rate is an order of magnitude faster than that of previously reported devices for physical random bit generators with verified randomness. This means that the performance of random number generators can be greatly improved by using chaotic laser devices as physical entropy sources.

  6. A semiconductor nanowire Josephson junction microwave laser

    Science.gov (United States)

    Cassidy, Maja; Uilhoorn, Willemijn; Kroll, James; de Jong, Damaz; van Woerkom, David; Nygard, Jesper; Krogstrup, Peter; Kouwenhoven, Leo

    We present measurements of microwave lasing from a single Al/InAs/Al nanowire Josephson junction strongly coupled to a high quality factor superconducting cavity. Application of a DC bias voltage to the Josephson junction results in photon emission into the cavity when the bias voltage is equal to a multiple of the cavity frequency. At large voltage biases, the strong non-linearity of the circuit allows for efficient down conversion of high frequency microwave photons down to multiple photons at the fundamental frequency of the cavity. In this regime, the emission linewidth narrows significantly below the bare cavity linewidth to 50%. The junction-cavity coupling and laser emission can be tuned rapidly via an external gate, making it suitable to be integrated into a scalable qubit architecture as a versatile source of coherent microwave radiation. This work has been supported by the Netherlands Organisation for Scientific Research (NWO/OCW), Foundation for Fundamental Research on Matter (FOM), European Research Council (ERC), and Microsoft Corporation Station Q.

  7. COHERENT LIDAR SYSTEM BASED ON A SEMICONDUCTOR LASER AND AMPLIFIER

    DEFF Research Database (Denmark)

    2009-01-01

    The present invention relates to a compact, reliable and low-cost coherent LIDAR (Light Detection And Ranging) system for remote wind-speed determination, determination of particle concentration, and/or temperature based on an all semiconductor light source and related methods. The present...... invention provides a coherent LIDAR system comprising a semiconductor laser for emission of a measurement beam of electromagnetic radiation directed towards a measurement volume for illumination of particles in the measurement volume, a reference beam generator for generation of a reference beam, a detector...... for generation of a detector signal by mixing of the reference beam with light emitted from the particles in the measurement volume illuminated by the measurement beam, and a signal processor for generating a velocity signal corresponding to the velocity of the particles based on the detector signal....

  8. Intrinsic Bistability and Critical Slowing in Tm3+/Yb3+ Codoped Laser Crystal with the Photon Avalanche Mechanism

    International Nuclear Information System (INIS)

    Li, Li; Li-Xue, Chen; Xin-Lu, Zhang

    2009-01-01

    We present theoretically a novel intrinsic optical bistability (IOB) in the Tm 3+ /Yb 3+ codoped system with a photon avalanche mechanism. Numerical simulations based on the rate equation model demonstrate distinct IOB hysteresis and critical slowing dynamics around the avalanche thresholds. Such an IOB characteristic in Tm 3+ /Yb 3+ codoped crystal has potential applications in solid-state bistable optical displays and luminescence switchers in visible-infrared spectra. (fundamental areas of phenomenology (including applications))

  9. Diagnostic studies of molecular plasmas using mid-infrared semiconductor lasers

    NARCIS (Netherlands)

    Röpcke, J.; Welzel, S.; Lang, N.; Hempel, F.; Gatilova, L.; Guaitella, O.; Rousseau, A.; Davies, P.B.

    2008-01-01

    Within the last decade mid-infrared absorption spectroscopy between 3 and 20 µm, known as infrared laser absorption spectroscopy (IRLAS) and based on tuneable semiconductor lasers, namely lead salt diode lasers, often called tuneable diode lasers (TDL), and quantum cascade lasers (QCL) has

  10. Modeling bidirectionally coupled single-mode semiconductor lasers

    International Nuclear Information System (INIS)

    Mulet, Josep; Masoller, Cristina; Mirasso, Claudio R.

    2002-01-01

    We develop a dynamical model suitable for the description of two mutually coupled semiconductor lasers in a face-to-face configuration. Our study considers the propagation of the electric field along the compound system as well as the evolution of the carrier densities within each semiconductor laser. Mutual injection, passive optical feedback, and multiple reflections are accounted for in this framework, although under weak to moderate coupling conditions. We systematically describe the effect of the coupling strength on the spectrum of monochromatic solutions and on the respective dynamical behavior. By assuming single-longitudinal-mode operation, weak mutual coupling and slowly varying approximation, the dynamical model can be reduced to rate equations describing the mutual injection from one laser to its counterpart and vice versa. A good agreement between the complete and simplified models is found for small coupling. For larger coupling, higher-order terms lead to a smaller threshold reduction, reflected itself in the spectrum of the monochromatic solutions and in the dynamics of the optical power

  11. An electrically injected rolled-up semiconductor tube laser

    Energy Technology Data Exchange (ETDEWEB)

    Dastjerdi, M. H. T.; Djavid, M.; Mi, Z., E-mail: zetian.mi@mcgill.ca [Department of Electrical and Computer Engineering, McGill University, 3480 University Street, Montreal, Quebec H3A 0E9 (Canada)

    2015-01-12

    We have demonstrated electrically injected rolled-up semiconductor tube lasers, which are formed when a coherently strained InGaAs/InGaAsP quantum well heterostructure is selectively released from the underlying InP substrate. The device exhibits strong coherent emission in the wavelength range of ∼1.5 μm. A lasing threshold of ∼1.05 mA is measured for a rolled-up tube with a diameter of ∼5 μm and wall thickness of ∼140 nm at 80 K. The Purcell factor is estimated to be ∼4.3.

  12. Effective Linewidth of Semiconductor Lasers for Coherent Optical Data Links

    DEFF Research Database (Denmark)

    Iglesias Olmedo, Miguel; Pang, Xiaodan; Schatz, Richard

    2016-01-01

    name “Effective Linewidth”. We derive this figure of merit analytically, explore it by numerical simulations and experimentally validate our results by transmitting a 28 Gbaud DP-16QAM over an optical link. Our investigations cover the use of semiconductor lasers both in the transmitter side...... and as a local oscillator at the receiver. The obtained results show that our proposed “effective linewidth” is easy to measure and accounts for frequency noise more accurately, and hence the penalties associated to phase noise in the received signal....

  13. Monolithic integration of microfluidic channels and semiconductor lasers

    Science.gov (United States)

    Cran-McGreehin, Simon J.; Dholakia, Kishan; Krauss, Thomas F.

    2006-08-01

    We present a fabrication method for the monolithic integration of microfluidic channels into semiconductor laser material. Lasers are designed to couple directly into the microfluidic channel, allowing submerged particles pass through the output beams of the lasers. The interaction between particles in the channel and the lasers, operated in either forward or reverse bias, allows for particle detection, and the optical forces can be used to trap and move particles. Both interrogation and manipulation are made more amenable for lab-on-a-chip applications through monolithic integration. The devices are very small, they require no external optical components, have perfect intrinsic alignment, and can be created with virtually any planar configuration of lasers in order to perform a variety of tasks. Their operation requires no optical expertise and only low electrical power, thus making them suitable for computer interfacing and automation. Insulating the pn junctions from the fluid is the key challenge, which is overcome by using photo-definable SU8-2000 polymer.

  14. Design and construct of a tunable semiconductor laser

    Directory of Open Access Journals (Sweden)

    J. Sabbaghzadeh

    2000-06-01

    Full Text Available   In this paper we explain in detail the design of a semiconductor laser coupled with the reflected beams from a grating. Since the beams reflected are diffracted at different angles, only one component of them can be resonated in the cavity. This technique reduces the output frequency of the laser and increases its stability.   Since this system has various applications in the spectroscopy, gas concentrations, air pollution measurements, investigation of atomic and molecular structure, and so on, system is believed to be simple and accurate. This design is made for the first time in Iran and its reliability has been tested by the measurement of the rubidium atom, and the result is given.

  15. The dynamical complexity of optically injected semiconductor lasers

    International Nuclear Information System (INIS)

    Wieczorek, S.; Krauskopf, B.; Simpson, T.B.; Lenstra, D.

    2005-01-01

    This report presents a modern approach to the theoretical and experimental study of complex nonlinear behavior of a semiconductor laser with optical injection-an example of a widely applied and technologically relevant forced nonlinear oscillator. We show that the careful bifurcation analysis of a rate equation model yields (i) a deeper understanding of already studied physical phenomena, and (ii) the discovery of new dynamical effects, such as multipulse excitability. Different instabilities, cascades of bifurcations, multistability, and sudden chaotic transitions, which are often viewed as independent, are in fact logically connected into a consistent web of bifurcations via special points called organizing centers. This theoretical bifurcation analysis has predictive power, which manifests itself in good agreement with experimental measurements over a wide range of parameters and diversity of dynamics. While it is dealing with the specific system of an optically injected laser, our work constitutes the state-of-the-art in the understanding and modeling of a nonlinear physical system in general

  16. All-metal coupling and package of semiconductor laser and amplifier with optical fiber

    International Nuclear Information System (INIS)

    Xu Fenglan; Li Lina; Zhang Yueqing

    1992-01-01

    The semiconductor laser and optical amplifier made by Changchun Institute of Physics coupled with optical fiber by use of all-metal coupling are represented. The net gain of semiconductor laser amplifier with optical fiber is 14 ∼18 dB

  17. Controlling the emission wavelength in group III-V semiconductor laser diodes

    KAUST Repository

    Ooi, Boon S.; Majid, Mohammed Abdul; Afandy, Rami; Aljabr, Ahmad

    2016-01-01

    Methods are provided for modifying the emission wavelength of a semiconductor quantum well laser diode, e.g. by blue shifting the emission wavelength. The methods can be applied to a variety of semiconductor quantum well laser diodes, e.g. group III

  18. Nanonewton thrust measurement of photon pressure propulsion using semiconductor laser

    Science.gov (United States)

    Iwami, K.; Akazawa, Taku; Ohtsuka, Tomohiro; Nishida, Hiroyuki; Umeda, Norihiro

    2011-09-01

    To evaluate the thrust produced by photon pressure emitted from a 100 W class continuous-wave semiconductor laser, a torsion-balance precise thrust stand is designed and tested. Photon emission propulsion using semiconductor light sources attract interests as a possible candidate for deep-space propellant-less propulsion and attitude control system. However, the thrust produced by photon emission as large as several ten nanonewtons requires precise thrust stand. A resonant method is adopted to enhance the sensitivity of the biflier torsional-spring thrust stand. The torsional spring constant and the resonant of the stand is 1.245 × 10-3 Nm/rad and 0.118 Hz, respectively. The experimental results showed good agreement with the theoretical estimation. The thrust efficiency for photon propulsion was also defined. A maximum thrust of 499 nN was produced by the laser with 208 W input power (75 W of optical output) corresponding to a thrust efficiency of 36.7%. The minimum detectable thrust of the stand was estimated to be 2.62 nN under oscillation at a frequency close to resonance.

  19. Construction of an optical semiconductor amplifier starting from a Fabry-Perot semiconductor laser; Construccion de un amplificador optico de semiconductor a partir de un laser de semiconductor Fabry-Perot

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, E.; Soto, H.; Marquez, H.; Valles V, N. [Departamento de Electronica y Telecomunicaciones, Centro de Investigacion Cientifica y de Educacion Superior de Ensenada. Km. 107, Carretera Tijuana-Ensenada, 22860 Ensenada, Baja California (Mexico)

    2000-07-01

    A methodology to convert a semiconductor laser Fabry-Perot (SL-FP) in a semiconductor optical amplifier (SOA) is presented. In order to suppress the cavity resonant an optical thin film coating was deposited on the facets of the SL-FP. The experiment was carried out putting on service a new monitoring technique that consist in the observation of the laser power spectrum during the antireflection coatings deposition. This allows to determine the moment were the facets reflectivity is minimum. The SOA obtained was characterized for different polarization currents. (Author)

  20. Semiconductor

    International Nuclear Information System (INIS)

    2000-01-01

    This book deals with process and measurement of semiconductor. It contains 20 chapters, which goes as follows; semiconductor industry, introduction of semiconductor manufacturing, yield of semiconductor process, materials, crystal growth and a wafer forming, PN, control pollution, oxidation, photomasking photoresist chemistry, photomasking technologies, diffusion and ion injection, chemical vapor deposition, metallization, wafer test and way of evaluation, semiconductor elements, integrated circuit and semiconductor circuit technology.

  1. Advanced excimer laser technologies enable green semiconductor manufacturing

    Science.gov (United States)

    Fukuda, Hitomi; Yoo, Youngsun; Minegishi, Yuji; Hisanaga, Naoto; Enami, Tatsuo

    2014-03-01

    "Green" has fast become an important and pervasive topic throughout many industries worldwide. Many companies, especially in the manufacturing industries, have taken steps to integrate green initiatives into their high-level corporate strategies. Governments have also been active in implementing various initiatives designed to increase corporate responsibility and accountability towards environmental issues. In the semiconductor manufacturing industry, there are growing concerns over future environmental impact as enormous fabs expand and new generation of equipments become larger and more powerful. To address these concerns, Gigaphoton has implemented various green initiatives for many years under the EcoPhoton™ program. The objective of this program is to drive innovations in technology and services that enable manufacturers to significantly reduce both the financial and environmental "green cost" of laser operations in high-volume manufacturing environment (HVM) - primarily focusing on electricity, gas and heat management costs. One example of such innovation is Gigaphoton's Injection-Lock system, which reduces electricity and gas utilization costs of the laser by up to 50%. Furthermore, to support the industry's transition from 300mm to the next generation 450mm wafers, technologies are being developed to create lasers that offer double the output power from 60W to 120W, but reducing electricity and gas consumption by another 50%. This means that the efficiency of lasers can be improve by up to 4 times in 450mm wafer production environments. Other future innovations include the introduction of totally Heliumfree Excimer lasers that utilize Nitrogen gas as its replacement for optical module purging. This paper discusses these and other innovations by Gigaphoton to enable green manufacturing.

  2. Deep-red semiconductor monolithic mode-locked lasers

    International Nuclear Information System (INIS)

    Kong, L.; Bajek, D.; White, S. E.; Forrest, A. F.; Cataluna, M. A.; Wang, H. L.; Pan, J. Q.; Wang, X. L.; Cui, B. F.; Ding, Y.

    2014-01-01

    A deep-red semiconductor monolithic mode-locked laser is demonstrated. Multi-section laser diodes based on an AlGaAs multi-quantum-well structure were passively mode-locked, enabling the generation of picosecond optical pulses at 752 nm, at pulse repetition rates of 19.37 GHz. An investigation of the dependence of the pulse duration as a function of reverse bias revealed a predominantly exponential decay trend of the pulse duration, varying from 10.5 ps down to 3.5 ps, which can be associated with the concomitant reduction of absorption recovery time with increasing applied field. A 30-MHz-tunability of the pulse repetition rate with bias conditions is also reported. The demonstration of such a compact, efficient and versatile ultrafast laser in this spectral region paves the way for its deployment in a wide range of applications such as biomedical microscopy, pulsed terahertz generation as well as microwave and millimeter-wave generation, with further impact on sensing, imaging and optical communications

  3. Multiclustered chimeras in large semiconductor laser arrays with nonlocal interactions

    Science.gov (United States)

    Shena, J.; Hizanidis, J.; Hövel, P.; Tsironis, G. P.

    2017-09-01

    The dynamics of a large array of coupled semiconductor lasers is studied numerically for a nonlocal coupling scheme. Our focus is on chimera states, a self-organized spatiotemporal pattern of coexisting coherence and incoherence. In laser systems, such states have been previously found for global and nearest-neighbor coupling, mainly in small networks. The technological advantage of large arrays has motivated us to study a system of 200 nonlocally coupled lasers with respect to the emerging collective dynamics. Moreover, the nonlocal nature of the coupling allows us to obtain robust chimera states with multiple (in)coherent domains. The crucial parameters are the coupling strength, the coupling phase and the range of the nonlocal interaction. We find that multiclustered chimera states exist in a wide region of the parameter space and we provide quantitative characterization for the obtained spatiotemporal patterns. By proposing two different experimental setups for the realization of the nonlocal coupling scheme, we are confident that our results can be confirmed in the laboratory.

  4. Reversibly Bistable Flexible Electronics

    KAUST Repository

    Alfaraj, Nasir

    2015-05-01

    Introducing the notion of transformational silicon electronics has paved the way for integrating various applications with silicon-based, modern, high-performance electronic circuits that are mechanically flexible and optically semitransparent. While maintaining large-scale production and prototyping rapidity, this flexible and translucent scheme demonstrates the potential to transform conventionally stiff electronic devices into thin and foldable ones without compromising long-term performance and reliability. In this work, we report on the fabrication and characterization of reversibly bistable flexible electronic switches that utilize flexible n-channel metal-oxide-semiconductor field-effect transistors. The transistors are fabricated initially on rigid (100) silicon substrates before they are peeled off. They can be used to control flexible batches of light-emitting diodes, demonstrating both the relative ease of scaling at minimum cost and maximum reliability and the feasibility of integration. The peeled-off silicon fabric is about 25 µm thick. The fabricated devices are transferred to a reversibly bistable flexible platform through which, for example, a flexible smartphone can be wrapped around a user’s wrist and can also be set back to its original mechanical position. Buckling and cyclic bending of such host platforms brings a completely new dimension to the development of flexible electronics, especially rollable displays.

  5. Optically pumped semiconductor lasers: Conception and characterization of a single mode source for Cesium atoms manipulation

    International Nuclear Information System (INIS)

    Cocquelin, B.

    2009-02-01

    Lasers currently used in atomic clocks or inertial sensors are suffering from a lack of power, narrow linewidth or compactness for future spatial missions. Optically pumped semiconductor lasers, which combine the approach of classical solid state lasers and the engineering of semiconductor laser, are considered here as a candidate to a metrological laser source dedicated to the manipulation of Cesium atoms in these instruments. These lasers have demonstrated high power laser emission in a circular single transverse mode, as well as single longitudinal mode emission, favoured by the semiconductor structure and the external cavity design. We study the definition and the characterization of a proper semiconductor structure for the cooling and the detection of Cesium atoms at 852 nm. A compact and robust prototype tunable on the Cesium D2 hyperfine structure is built. The laser frequency is locked to an atomic transition thanks to a saturated absorption setup. The emission spectral properties are investigated, with a particular attention to the laser frequency noise and the laser linewidth. Finally, we describe and model the thermal properties of the semiconductor structure, which enables the simulation of the laser power characteristic. The experimental parameters are optimised to obtain the maximum output power with our structure. Thanks to our analysis, we propose several ways to overcome these limitations, by reducing the structure heating. (authors)

  6. Controlling the emission wavelength in group III-V semiconductor laser diodes

    KAUST Repository

    Ooi, Boon S.

    2016-12-29

    Methods are provided for modifying the emission wavelength of a semiconductor quantum well laser diode, e.g. by blue shifting the emission wavelength. The methods can be applied to a variety of semiconductor quantum well laser diodes, e.g. group III-V semiconductor quantum wells. The group III-V semiconductor can include AlSb, AlAs, Aln, AlP, BN, GaSb, GaAs, GaN, GaP, InSb, InAs, InN, and InP, and group III-V ternary semiconductors alloys such as AlxGai.xAs. The methods can results in a blue shifting of about 20 meV to 350 meV, which can be used for example to make group III-V semiconductor quantum well laser diodes with an emission that is orange or yellow. Methods of making semiconductor quantum well laser diodes and semiconductor quantum well laser diodes made therefrom are also provided.

  7. Comprehensive and fully self-consistent modeling of modern semiconductor lasers

    International Nuclear Information System (INIS)

    Nakwaski, W.; Sarzał, R. P.

    2016-01-01

    The fully self-consistent model of modern semiconductor lasers used to design their advanced structures and to understand more deeply their properties is given in the present paper. Operation of semiconductor lasers depends not only on many optical, electrical, thermal, recombination, and sometimes mechanical phenomena taking place within their volumes but also on numerous mutual interactions between these phenomena. Their experimental investigation is quite complex, mostly because of miniature device sizes. Therefore, the most convenient and exact method to analyze expected laser operation and to determine laser optimal structures for various applications is to examine the details of their performance with the aid of a simulation of laser operation in various considered conditions. Such a simulation of an operation of semiconductor lasers is presented in this paper in a full complexity of all mutual interactions between the above individual physical processes. In particular, the hole-burning effect has been discussed. The impacts on laser performance introduced by oxide apertures (their sizes and localization) have been analyzed in detail. Also, some important details concerning the operation of various types of semiconductor lasers are discussed. The results of some applications of semiconductor lasers are shown for successive laser structures. (paper)

  8. Si-Based Germanium Tin Semiconductor Lasers for Optoelectronic Applications

    Science.gov (United States)

    Al-Kabi, Sattar H. Sweilim

    Silicon-based materials and optoelectronic devices are of great interest as they could be monolithically integrated in the current Si complementary metal-oxide-semiconductor (CMOS) processes. The integration of optoelectronic components on the CMOS platform has long been limited due to the unavailability of Si-based laser sources. A Si-based monolithic laser is highly desirable for full integration of Si photonics chip. In this work, Si-based germanium-tin (GeSn) lasers have been demonstrated as direct bandgap group-IV laser sources. This opens a completely new avenue from the traditional III-V integration approach. In this work, the material and optical properties of GeSn alloys were comprehensively studied. The GeSn films were grown on Ge-buffered Si substrates in a reduced pressure chemical vapor deposition system with low-cost SnCl4 and GeH4 precursors. A systematic study was done for thin GeSn films (thickness 400 nm) with Sn composition 5 to 17.5%. The room temperature photoluminescence (PL) spectra were measured that showed a gradual shift of emission peaks towards longer wavelength as Sn composition increases. Strong PL intensity and low defect density indicated high material quality. Moreover, the PL study of n-doped samples showed bandgap narrowing compared to the unintentionally p-doped (boron) thin films with similar Sn compositions. Finally, optically pumped GeSn lasers on Si with broad wavelength coverage from 2 to 3 mum were demonstrated using high-quality GeSn films with Sn compositions up to 17.5%. The achieved maximum Sn composition of 17.5% broke the acknowledged Sn incorporation limit using similar deposition chemistry. The highest lasing temperature was measured at 180 K with an active layer thickness as thin as 270 nm. The unprecedented lasing performance is due to the achievement of high material quality and a robust fabrication process. The results reported in this work show a major advancement towards Si-based electrically pumped mid

  9. Photoacoustic Techniques for Trace Gas Sensing Based on Semiconductor Laser Sources

    Directory of Open Access Journals (Sweden)

    Vincenzo Spagnolo

    2009-12-01

    Full Text Available The paper provides an overview on the use of photoacoustic sensors based on semiconductor laser sources for the detection of trace gases. We review the results obtained using standard, differential and quartz enhanced photoacoustic techniques.

  10. Identification of amplitude and timing jitter in external-cavity mode-locked semiconductor lasers

    DEFF Research Database (Denmark)

    Mulet, Josep; Mørk, Jesper; Kroh, Marcel

    2004-01-01

    We theoretically and experimentally investigate the dynamics of external-cavity mode-locked semiconductor lasers, focusing on stability properties, optimization of pulsewidth and timing jitter. A new numerical approach allows to clearly separate timing and amplitude jitter....

  11. Emergence of resonant mode-locking via delayed feedback in quantum dot semiconductor lasers.

    Science.gov (United States)

    Tykalewicz, B; Goulding, D; Hegarty, S P; Huyet, G; Erneux, T; Kelleher, B; Viktorov, E A

    2016-02-22

    With conventional semiconductor lasers undergoing external optical feedback, a chaotic output is typically observed even for moderate levels of the feedback strength. In this paper we examine single mode quantum dot lasers under strong optical feedback conditions and show that an entirely new dynamical regime is found consisting of spontaneous mode-locking via a resonance between the relaxation oscillation frequency and the external cavity repetition rate. Experimental observations are supported by detailed numerical simulations of rate equations appropriate for this laser type. The phenomenon constitutes an entirely new mode-locking mechanism in semiconductor lasers.

  12. Quantifying Information Flow between Two Chaotic Semiconductor Lasers Using Symbolic Transfer Entropy

    International Nuclear Information System (INIS)

    Li Nian-Qiang; Pan Wei; Yan Lian-Shan; Luo Bin; Xu Ming-Feng; Tang Yi-Long

    2012-01-01

    Symbolic transfer entropy (STE) is employed to quantify the dominant direction of information flow between two chaotic-semiconductor-laser time series. The information flow in unidirectionally and bidirectionally coupled systems was analyzed systematically. Numerical results show that the dependence relationship can be revealed if there exists any coupling between two chaotic semiconductor lasers. More importantly, in both unsynchronized and good synchronization regimes, the STE can be used to quantify the direction of information flow between the lasers, although the former case leads to a better identification. The results thus establish STE as an effective tool for quantifying the direction of information flow between chaotic-laser-based systems

  13. Extracting physical properties of arbitrarily shaped laser-doped micro-scale areas in semiconductors

    International Nuclear Information System (INIS)

    Heinrich, Martin; Kluska, Sven; Hameiri, Ziv; Hoex, Bram; Aberle, Armin G.

    2013-01-01

    We present a method that allows the extraction of relevant physical properties such as sheet resistance and dopant profile from arbitrarily shaped laser-doped micro-scale areas formed in semiconductors with a focused pulsed laser beam. The key feature of the method is to use large laser-doped areas with an identical average number of laser pulses per area (laser pulse density) as the arbitrarily shaped areas. The method is verified using sheet resistance measurements on laser-doped silicon samples. Furthermore, the method is extended to doping with continuous-wave lasers by using the average number of passes per area or density of passes

  14. All-polymer organic semiconductor laser chips: Parallel fabrication and encapsulation

    DEFF Research Database (Denmark)

    Vannahme, Christoph; Klinkhammer, Sönke; Christiansen, Mads Brøkner

    2010-01-01

    Organic semiconductor lasers are of particular interest as tunable visible laser light sources. For bringing those to market encapsulation is needed to ensure practicable lifetimes. Additionally, fabrication technologies suitable for mass production must be used. We introduce all-polymer chips...... comprising encapsulated distributed feedback organic semiconductor lasers. Several chips are fabricated in parallel by thermal nanoimprint of the feedback grating on 4? wafer scale out of poly(methyl methacrylate) (PMMA) and cyclic olefin copolymer (COC). The lasers consisting of the organic semiconductor...... tris(8- hydroxyquinoline) aluminum (Alq3) doped with the laser dye 4-dicyanomethylene-2- methyl-6-(p-dimethylaminostyril)-4H-pyrane (DCM) are hermetically sealed by thermally bonding a polymer lid. The organic thin film is placed in a basin within the substrate and is not in direct contact to the lid...

  15. Quantum theory of the optical and electronic properties of semiconductors

    CERN Document Server

    Haug, Hartmut

    2009-01-01

    This invaluable textbook presents the basic elements needed to understand and research into semiconductor physics. It deals with elementary excitations in bulk and low-dimensional semiconductors, including quantum wells, quantum wires and quantum dots. The basic principles underlying optical nonlinearities are developed, including excitonic and many-body plasma effects. Fundamentals of optical bistability, semiconductor lasers, femtosecond excitation, the optical Stark effect, the semiconductor photon echo, magneto-optic effects, as well as bulk and quantum-confined Franz-Keldysh effects, are covered. The material is presented in sufficient detail for graduate students and researchers with a general background in quantum mechanics.This fifth edition includes an additional chapter on 'Quantum Optical Effects' where the theory of quantum optical effects in semiconductors is detailed. Besides deriving the 'semiconductor luminescence equations' and the expression for the stationary luminescence spectrum, the resu...

  16. Broadband tunability of gain-flattened quantum-well semiconductor lasers with an external grating

    International Nuclear Information System (INIS)

    Mittelstein, M.; Mehuys, D.; Yariv, A.; Sarfaty, R.; Ungar, J.E.

    1989-01-01

    Semiconductor injection lasers are known to be tunable over a range of order kΒ · T. Quantum-well lasers, in particular, are shown to exhibit flattened, broadband gain spectra at a particular pumping condition. The gain requirement for a grating-tuned external cavity configuration is examined and is applied to a semiconductor quantum-well laser with an optimized length of gain region. The coupled-cavity formalism is employed to examine the conditions for continuous tuning. The possible tuning range of double-heterostructure lasers is compared to that of quantum-well lasers. The predicted broadband tunability of quantum-well lasers is confirmed experimentally by grating-tuning of uncoated lasers exceeding 120 nm, with single, longitudinal mode output power exceeding 300 mW

  17. Influence of temperature on the spectral characteristics of semiconductor lasers in the visible range

    Science.gov (United States)

    Adamov, A. A.; Baranov, M. S.; Khramov, V. N.

    2018-04-01

    The results of studies on the effect of temperature on the output spectral characteristics of continuous semiconductor lasers of the visible range are presented. The paper presents the results of studying the spectral-optical radiation parameters of semiconductor lasers, their coherence lengths, and the dependence of the position of the spectral peak of the wavelength on temperature. This is necessary for the selection of the most optimal laser in order to use it for medical ophthalmologic diagnosis. The experiment was carried out using semiconductor laser modules based on a laser diode. The spectra were recorded by using a two-channel automated spectral complex based on the MDR-23 monochromator. Spectral dependences on the temperature of semiconductor lasers are obtained, in the range from 300 to 370 K. The possibility of determining the internal damage to the stabilization of laser modules without opening the case is shown, but only with the use of their spectral characteristics. The obtained data allow taking into account temperature characteristics and further optimization of parameters of such lasers when used in medical practice, in particular, in ophthalmologic diagnostics.

  18. A study on the optical parts for a semiconductor laser module

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Jun-Girl; Lee, Dong-Kil; Kim, Yang-Gyu; Lee, Kwang-Hoon; Park, Young-Sik [Korea Photonics Technology Institute, Gwangju (Korea, Republic of); Jang, Kwang-Ho [Hanvit Optoline, Gwangju (Korea, Republic of); Kang, Seung-Goo [COSET, Gwangju (Korea, Republic of)

    2014-11-15

    A semiconductor laser module consists of a LD (laser diode) chip that generates a laser beam, two cylindrical lenses to collimate the laser beam, a high-reflection mirror to produce a large output by collecting the laser beam, a collimator lens to guide the laser beam to an optical fiber and a protection filter to block reflected laser light that might damage the LD chip. The cylindrical lenses used in a semiconductor laser module are defined as FACs (fast axis collimators) and SACs (slow axis collimators) and are attached to the system module to control the shape of the laser beam. The FAC lens and the SAC lens are made of a glass material to protect the lenses from thermal deformation. In addition, they have aspheric shapes to improve optical performances. This paper presents a mold core grinding process for an asymmetrical aspheric lens and a GMP (glass molding press), what can be used to make aspheric cylindrical lenses for use as FACs or SACs, and a protection filter made by using IAD (ion-beam-assisted deposition). Finally, we developed the aspheric cylindrical lenses and the protection filter for a 10-W semiconductor laser module.

  19. Plastic lab-on-a-chip for fluorescence excitation with integrated organic semiconductor lasers.

    Science.gov (United States)

    Vannahme, Christoph; Klinkhammer, Sönke; Lemmer, Uli; Mappes, Timo

    2011-04-25

    Laser light excitation of fluorescent markers offers highly sensitive and specific analysis for bio-medical or chemical analysis. To profit from these advantages for applications in the field or at the point-of-care, a plastic lab-on-a-chip with integrated organic semiconductor lasers is presented here. First order distributed feedback lasers based on the organic semiconductor tris(8-hydroxyquinoline) aluminum (Alq3) doped with the laser dye 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyril)-4H-pyrane (DCM), deep ultraviolet induced waveguides, and a nanostructured microfluidic channel are integrated into a poly(methyl methacrylate) (PMMA) substrate. A simple and parallel fabrication process is used comprising thermal imprint, DUV exposure, evaporation of the laser material, and sealing by thermal bonding. The excitation of two fluorescent marker model systems including labeled antibodies with light emitted by integrated lasers is demonstrated.

  20. Instability of stationary lasing and self-starting mode locking in external-cavity semiconductor lasers

    International Nuclear Information System (INIS)

    Smetanin, Igor V; Vasil'ev, Petr P

    2009-01-01

    Parameters of external-cavity semiconductor lasers, when the stationary lasing becomes unstable, were analysed within the framework of a theoretical model of self-starting mode locking. In this case, a train of ultrashort pulses can be generated due to intrinsic nonlinearities of the laser medium. A decisive role of the transverse optical field nonuniformity, pump rate, and gain spectral bandwidth in the development of the instability of stationary lasing was demonstrated. (control of laser radiation parameters)

  1. Periodic dark pulse emission induced by delayed feedback in a quantum well semiconductor laser

    Directory of Open Access Journals (Sweden)

    L. Li

    2012-12-01

    Full Text Available We report the experimental observation of periodic dark pulse emission in a quantum-well semiconductor laser with delayed optical feedback. We found that under appropriate operation conditions the laser can also emit a stable train of dark pulses. The repetition frequency of the dark pulse is determined by the external cavity length. Splitting of the dark pulse was also observed. We speculate that the observed dark pulse is a kind of temporal cavity soliton formed in the laser.

  2. Semiconductor lasers with a continuous tuning range above 100 nm in the nearest IR spectral region

    Energy Technology Data Exchange (ETDEWEB)

    Kostin, Yu O; Lobintsov, A A; Shramenko, M V [OOO ' Opton' , Moscow (Russian Federation); Ladugin, M A; Marmalyuk, A A [Open Joint-Stock Company M.F. Stel' makh Polyus Research Institute, Moscow (Russian Federation); Chamorovsky, A Yu [Superlum Ltd., Unit B3, Fota Point Enterprise Park, Carrigtwohill, Co Cork (Ireland); Yakubovich, S D [Moscow State Institute of Radio-Engineering, Electronics and Automation (Technical University), Moscow (Russian Federation)

    2015-08-31

    We have developed two new types of lasers based on quantum-confined semiconductor optical amplifiers with an acousto-optic tunable filter in an external fibre ring cavity. The lasers offer continuous wavelength tuning ranges from 780 to 885 and from 880 to 1010 nm, 20 mW of cw output power, and a tuning rate up to 10{sup 4} nm s{sup -1} at an instantaneous spectral linewidth less than 0.1 nm. (lasers)

  3. Experimental control of power dropouts by current modulation in a semiconductor laser with optical feedback

    International Nuclear Information System (INIS)

    Ticos, Catalin M; Andrei, Ionut R; Pascu, Mihail L; Bulinski, Mircea

    2011-01-01

    The injection current of an external-cavity semiconductor laser working in a regime of low-frequency fluctuations (LFFs) is modulated at several MHz. The rate of power dropouts in the laser emission is correlated with the amplitude and frequency of the modulating signal. The occurrence of dropouts becomes more regular when the laser is driven at 7 MHz, which is close to the dominant frequency of dropouts in the solitary laser. Driving the laser at 10 MHz also induces dropouts with a periodicity of 0.1 μs, resulting in LFFs with two dominant frequencies.

  4. Laser interferometric method for determining the carrier diffusion length in semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Manukhov, V. V. [Saint Petersburg State University (Russian Federation); Fedortsov, A. B.; Ivanov, A. S., E-mail: ivaleks58@gmail.com [Saint Petersburg Mining University (Russian Federation)

    2015-09-15

    A new laser interferometric method for measuring the carrier diffusion length in semiconductors is proposed. The method is based on the interference–absorption interaction of two laser radiations in a semiconductor. Injected radiation generates additional carriers in a semiconductor, which causes a change in the material’s optical constants and modulation of the probing radiation passed through the sample. When changing the distance between carrier generation and probing points, a decrease in the carrier concentration, which depends on the diffusion length, is recorded. The diffusion length is determined by comparing the experimental and theoretical dependences of the probe signal on the divergence of the injector and probe beams. The method is successfully tested on semiconductor samples with different thicknesses and surface states and can be used in scientific research and the electronics industry.

  5. Theory of semiconductor lasers from basis of quantum electronics to analyses of the mode competition phenomena and noise

    CERN Document Server

    Yamada, Minoru

    2014-01-01

    This book provides a unified and complete theory for semiconductor lasers, covering topics ranging from the principles of classical and quantum mechanics to highly advanced levels for readers who need to analyze the complicated operating characteristics generated in the real application of semiconductor lasers.   The author conducts a theoretical analysis especially on the instabilities involved in the operation of semiconductor lasers. A density matrix into the theory for semiconductor lasers is introduced and the formulation of an improved rate equation to help understand the mode competition phenomena which cause the optical external feedback noise is thoroughly described from the basic quantum mechanics. The derivation of the improved rate equation will allow readers to extend the analysis for the different types of semiconductor materials and laser structures they deal with.   This book is intended not only for students and academic researchers but also for engineers who develop lasers for the market, ...

  6. Bistable Reflective Etalon (BRET)

    National Research Council Canada - National Science Library

    Shellenbarger, Zane

    2003-01-01

    This project designed, fabricated, and characterized normal-incidence etalon structures at 1550 nm wavelength operation for application, as bistable elements, to photonic analog-to-digital conversion...

  7. Efficiency of soft tissue incision with a novel 445-nm semiconductor laser.

    Science.gov (United States)

    Braun, Andreas; Kettner, Moritz; Berthold, Michael; Wenzler, Johannes-Simon; Heymann, Paul Günther Baptist; Frankenberger, Roland

    2018-01-01

    Using a 445-nm semiconductor laser for tissue incision, an effective cut is expected due to the special absorption properties of blue laser light in soft tissues. The aim of the present study was the histological evaluation of tissue samples after incision with a 445-nm diode laser. Forty soft tissue specimens were obtained from pork oral mucosa and mounted on a motorized linear translation stage. The handpiece of a high-frequency surgery device, a 970-nm semiconductor laser, and a 445-nm semiconductor laser were connected to the slide, allowing a constant linear movement (2 mm/s) and the same distance of the working tip to the soft tissue's surface. Four incisions were made each: (I) 970-nm laser with conditioned fiber tip, contact mode at 3-W cw; (II-III): 445-nm laser with non-conditioned fiber tip, contact mode at 2-W cw, and non-contact mode (1 mm) at 2 W; and (IV): high-frequency surgery device with straight working tip, 90° angulation, contact mode at 50 W. Histological analysis was performed after H&E staining of the embedded specimens at 35-fold magnification. The comparison of the incision depths showed a significant difference depending on the laser wavelength and the selected laser parameters. The highest incision depth was achieved with the 445-nm laser contact mode (median depth 0.61 mm, min 0.26, max 1.17, interquartile range 0.58) (p laser, a higher cutting efficiency can be expected when compared with a 970-nm diode laser and high-frequency surgery. Even the 445-nm laser application in non-contact mode shows clinically acceptable incision depths without signs of extensive soft tissue denaturation.

  8. Frequency locking, quasiperiodicity, subharmonic bifurcations and chaos in high frequency modulated stripe geometry DH semiconductor lasers

    International Nuclear Information System (INIS)

    Zhao Yiguang

    1991-01-01

    The method of obtaining self-consistent solutions of the field equation and the rate equations of photon density and carrier concentration has been used to study frequecny locking, quasiperiodicity, subharmonic bifurcations and chaos in high frequency modulated stripe geometry DH semiconductor lasers. The results show that the chaotic behavior arises in self-pulsing stripe geometry semiconductor lasers. The route to chaos is not period-double, but quasiperiodicity to chaos. All of the results agree with the experiments. Some obscure points in previous theory about chaos have been cleared up

  9. Mode-Locked Semiconductor Lasers for Optical Communication Systems

    DEFF Research Database (Denmark)

    Yvind, Kresten; Larsson, David; Oxenløwe, Leif Katsuo

    2005-01-01

    We present investigations on 10 and 40 GHz monolithic mode-locked lasers for applications in optical communications systems. New all-active lasers with one to three quantum wells have been designed, fabricated and characterized....

  10. Modification of semiconductor materials using laser-produced ion streams additionally accelerated in the electric fields

    International Nuclear Information System (INIS)

    Rosinski, M.; Badziak, B.; Parys, P.; Wolowski, J.; Pisarek, M.

    2009-01-01

    The laser-produced ion stream may be attractive for direct ultra-low-energy ion implantation in thin layer of semiconductor for modification of electrical and optical properties of semiconductor devices. Application of electrostatic fields for acceleration and formation of laser-generated ion stream enables to control the ion stream parameters in broad energy and current density ranges. It also permits to remove the useless laser-produced ions from the ion stream designed for implantation. For acceleration of ions produced with the use of a low fluence repetitive laser system (Nd:glass: 2 Hz, pulse duration: 3.5 ns, pulse energy:∼0.5 J, power density: 10 10 W/cm 2 ) in IPPLM the special electrostatic system has been prepared. The laser-produced ions passing through the diaphragm (a ring-shaped slit in the HV box) have been accelerated in the system of electrodes. The accelerating voltage up to 40 kV, the distance of the diaphragm from the target, the diaphragm diameter and the gap width were changed for choosing the desired parameters (namely the energy band of the implanted ions) of the ion stream. The characteristics of laser-produced Ge ion streams were determined with the use of precise ion diagnostic methods, namely: electrostatic ion energy analyser and various ion collectors. The laser-produced and post-accelerated Ge ions have been used for implantation into semiconductor materials for nanocrystal fabrication. The characteristics of implanted samples were measured using AES

  11. Theory for passive mode-locking in semiconductor laser structures including the effects of self-phase modulation, dispersion and pulse collisions

    NARCIS (Netherlands)

    Koumans, R.G.M.P.; Roijen, van R.

    1996-01-01

    We present a theory for passive mode-locking in semiconductor laser structures using a semiconductor laser amplifier and absorber. The mode-locking system is described in terms of the different elements in the semiconductor laser structure. We derive mode-locking conditions and show how other

  12. Fiber optical laser spot microscope: A new concept for photoelectrochemical characterization of semiconductor electrodes

    OpenAIRE

    Carlsson, Per; Holmström, Bertil; Uosaki, Kohei; Kita, Hideaki

    1988-01-01

    A fiber optical laser spot microscope, which allows the simultaneous measurements of photocurrent and reflected light intensity or the measurement of laser spot photocurrent under the illumination of other light sources, has been developed to study semiconductor/electrolyte interfaces. The capability of this microscope was demonstrated on as-cleaved and Pt-treated p-InSe. The Pt treatment increased the photocurrent and improved the lateral resolution due to the increase of surface reaction ra...

  13. Mode-Locking in Broad-Area Semiconductor Lasers Enhanced by Picosecond-Pulse Injection

    OpenAIRE

    Kaiser, J; Fischer, I; Elsasser, W; Gehrig, E; Hess, O

    2004-01-01

    We present combined experimental and theoretical investigations of the picosecond emission dynamics of broad-area semiconductor lasers (BALs). We enhance the weak longitudinal self-mode-locking that is inherent to BALs by injecting a single optical 50-ps pulse, which triggers the output of a distinct regular train of 13-ps pulses. Modeling based on multimode Maxwell-Bloch equations illustrates how the dynamic interaction of the injected pulse with the internal laser field efficiently couples ...

  14. Bistable optical response of a nanoparticle heterodimer : Mechanism, phase diagram, and switching time

    NARCIS (Netherlands)

    Nugroho, Bintoro; Iskandar, Alexander; Malyshev, V.A.; Knoester, Jasper

    2013-01-01

    We conduct a theoretical study of the bistable optical response of a nanoparticle heterodimer comprised of a closely spaced semiconductor quantum dot and a metal nanoparticle. The bistable nature of the response results from the interplay between the quantum dot's optical nonlinearity and its

  15. Digitally tunable dual wavelength emission from semiconductor ring lasers with filtered optical feedback

    International Nuclear Information System (INIS)

    Khoder, Mulham; Verschaffelt, Guy; Nguimdo, Romain Modeste; Danckaert, Jan; Leijtens, Xaveer; Bolk, Jeroen

    2013-01-01

    We report on a novel integrated approach to obtain dual wavelength emission from a semiconductor laser based on on-chip filtered optical feedback. Using this approach, we show experiments and numerical simulations of dual wavelength emission of a semiconductor ring laser. The filtered optical feedback is realized on-chip by employing two arrayed waveguide gratings to split/recombine light into different wavelength channels. Semiconductor optical amplifiers are placed in the feedback loop in order to control the feedback strength of each wavelength channel independently. By tuning the current injected into each of the amplifiers, we can effectively cancel the gain difference between the wavelength channels due to fabrication and material dichroism, thus resulting in stable dual wavelength emission. We also explore the accuracy needed in the operational parameters to maintain this dual wavelength emission. (letter)

  16. Laser action on rare earth doped nitride semiconductor thin layers

    International Nuclear Information System (INIS)

    Oussif, A.; Diaf, M.

    2010-01-01

    Complete text of publication follows. The structure, chemical composition, properties, and their relationships in solids lay the foundation of materials science. Recently, great interest in rare-earth (RE)-doped wide-bandgap semiconductors, which combine the electronic properties of semiconductors with the unique luminescence features of RE ions, is from the fundamental standpoint of structure-composition-properties of solids. At first, a significant amount of work has been reported on the study of infrared emissions from Er 3+- doped semiconductors because Er 3+ exhibits luminescence at 1.54 μm, a wavelength used in optical communications. Since Steckl and Birkhahn first reported visible emission associated with Er from GaN:Er films, the RE-doped semiconductors have received considerable interest for possible application in light emitting devices. Molecular-beam epitaxy (MBE) and metalorganic chemical vapour deposition (MOCVD) have been used mainly to grow GaN host films. The RE dopants were typically incorporated into the host films by in situ doping during the growth or by ion implantation after the growth. GaN doped with rare-earth elements (RE) hold significant potential for applications in optical devices, since they show sharp intense luminescence which is only minimally affected by temperature variations. Among the various RE dopants, Eu seems to be the most interesting, since it yields red luminescence 622 nm which has not been realized in commercially available light emitting devices (LEDs) that use InGaN active layers. We have earlier reported single crystalline growth of Eu-doped GaN and nearly temperature independent red luminescence at 622 nm originating from the intra-4f-4f transition of the Eu 3+ ion. The red luminescence was analyzed and determined to be generated through trap-level-mediated energy transfer from the semiconductor host.

  17. Laser Doppler perfusion imaging with a complimentary metal oxide semiconductor image sensor

    NARCIS (Netherlands)

    Serov, Alexander; Steenbergen, Wiendelt; de Mul, F.F.M.

    2002-01-01

    We utilized a complimentary metal oxide semiconductor video camera for fast f low imaging with the laser Doppler technique. A single sensor is used for both observation of the area of interest and measurements of the interference signal caused by dynamic light scattering from moving particles inside

  18. Design and evaluation of modelocked semiconductor lasers for low noise and high stability

    DEFF Research Database (Denmark)

    Yvind, Kresten; Larsson, David; Christiansen, Lotte Jin

    2005-01-01

    We present work on design of monolithic mode-locked semiconductor lasers with focus on the gain medium. The use of highly inverted quantum wells in a low-loss waveguide enables both low quantum noise, low-chirped pulses and a large stability region. Broadband noise measurements are performed...

  19. Numerical investigations on the performance of external-cavity mode-locked semiconductor lasers

    DEFF Research Database (Denmark)

    Mulet, Josep; Mørk, Jesper

    2004-01-01

    The performance of an external-cavity mode-locked semiconductor laser is analyzed theoretically and numerically. Passive mode-locking is described using a fully-distributed time-domain model including fast effects, spectral hole burning and carrier heating. We provide optimization rules in order ...

  20. Analog direct-modulation behavior of semiconductor laser transmitters using optical FM demodulation

    NARCIS (Netherlands)

    Yabre, G.S.

    1998-01-01

    In this paper, we report a theoretical investigation of the analog modulation performance of a semiconductor laser transmitter which employs the direct optical FM demodulation. This analysis is based on the rate equations in which Langevin noise functions are included. The optical FM response has

  1. A theoretical analysis for gigabit/second pulse code modulation of semiconductor lasers

    DEFF Research Database (Denmark)

    Danielsen, Magnus

    1976-01-01

    Investigation of the rate equations of a semiconductor laser suggests that bit rates of 3-4 Gbit/s can be achieved. Delay, ringing transients, and charge-storage effects can be removed by adjusting the dc-bias current and the peak and width of the current pulse to values prescribed by simple...

  2. Single-mode very wide tunability in laterally coupled semiconductor lasers with electrically controlled reflectivities

    Science.gov (United States)

    Griffel, Giora; Chen, Howard Z.; Grave, Ilan; Yariv, Amnon

    1991-04-01

    The operation of a novel multisection structure comprised of laterally coupled gain-guided semiconductor lasers is demonstrated. It is shown that tunable single longitudinal mode operation can be achieved with a high degree of frequency selectivity. The device has a tuning range of 14.5 nm, the widest observed to date in a monolithic device.

  3. Return-map for low-frequency fluctuations in semiconductor lasers with optical feedback

    DEFF Research Database (Denmark)

    Mørk, Jesper; Sabbatier, H.; Sørensen, Mads Peter

    1999-01-01

    We show that the phenomenon of low-frequency fluctuations (LFF) , commonly observed in semiconductor lasers with optical feedback, can be explained by a simple return-map, implying a tremendous simplification in the description of the slow time-scale dynamics of the system. Experimentally observed...

  4. Study on biological effect on mice and use safety of 830 nm semiconductor laser

    International Nuclear Information System (INIS)

    Li Keqiu; Li Jian; Miao Xuhong; Liu Shujuan; Li Guang

    2006-01-01

    Objective: To study biological effect on mice by 830 nm semiconductor laser in different dosage, and determine the optimal irradiating dosage by observing and analyzing the immunoregulation and cytogenetical damage of mice after irradiation. Methods: The spleen and thymus areas of Kunming mice were irradiated in vitro by 830 nm semiconductor laser of 30 mW for 5 min, 10 min and 20 min per day respectively, then the blood samples were collected from orbital vein. Further, the spleen tissue and sternum marrow were collected soon after the mice were killed. Afterwards, IgG, dopamine, serotonin in serum were detected respectively. Besides these, the rate of lymphocyte transformation and the rate of micronuclei in marrow polychromatic erythrocytes were also determined. Results: With the extending of irradiating time, the detected factors changed differently. Statistically, there were differences in IgG concentration and the rate of lymphocyte transformation between 10 min group, 20 min group and control group respectively, but no difference between each experimental group were found. /compare with control group, serotonin concentration in 10 min group increased, and there was statistical difference between these two groups, while there was no difference in dopamine concentration among each group. Besides these, the rate of micronuclei in 20 min group increased. Conclusion: In this study, irradiation by semiconductor laser for appropriate time can improve immuno function of mice, but irradiation in high dosage will result in the damage of genetic material. The optimal time of irradiation by 830 nm semiconductor laser was 10 min. (authors)

  5. High gain semiconductor optical amplifier — Laser diode at visible wavelength

    KAUST Repository

    Shen, Chao; Lee, Changmin; Ng, Tien Khee; Nakamura, Shuji; Speck, James S.; DenBaars, Steven P.; Alyamani, Ahmed Y.; El-Desouki, Munir M.; Ooi, Boon S.

    2017-01-01

    We reported on the first experimental demonstration of a two-section semipolar InGaN-based laser diode with monolithically integrated semiconductor optical amplifier (SOA-LD). The onset of amplification effect was measured at 4V SOA bias (VSOA). The SOA-LD shows a large gain of 5.32 dB at Vsoa = 6 V.

  6. Ultrawideband pulse generation based on overshooting effect in gain-switched semiconductor laser

    DEFF Research Database (Denmark)

    Torres-Company, V.; Prince, Kamau; Tafur Monroy, Idelfonso

    2008-01-01

    We demonstrate an alternative procedure to achieve ultrawideband (UWB) radio-frequency (RF) doublet impulses. It is based on the overshooting effect appearing by biasing a semiconductor laser close to the threshold with a large-amplitude signal. Specifically, with an optical bandpass filter...... a reliable, easy, and low-cost alternative for RF UWB impulse generation....

  7. High gain semiconductor optical amplifier — Laser diode at visible wavelength

    KAUST Repository

    Shen, Chao

    2017-02-07

    We reported on the first experimental demonstration of a two-section semipolar InGaN-based laser diode with monolithically integrated semiconductor optical amplifier (SOA-LD). The onset of amplification effect was measured at 4V SOA bias (VSOA). The SOA-LD shows a large gain of 5.32 dB at Vsoa = 6 V.

  8. Linewidth broadening in a distributed feedback laser integrated with a semiconductor optical amplifier

    DEFF Research Database (Denmark)

    Champagne, A.; Camel, J.; Maciejko, R.

    2002-01-01

    The problem of the linewidth degradation in systems using distributed-feedback lasers together with strained-layer multi-quantum-well semiconductor optical amplifiers (SOAs) is examined. A modified expression for the linewidth in the case of antireflection-coated SOA output facets is derived and ...

  9. Spectral characteristics of DFB lasers in presence of a semiconductor optical amplifier

    DEFF Research Database (Denmark)

    Champagne, A.; Camel, J.; Maciejko, R.

    2002-01-01

    The problem of the linewidth degradation in systems using distributed-feedback lasers together with strained-layer multi-quantum-well semiconductor optical amplifiers (SOAs) is examined. A numerical model combining finite element calculations in the transverse x - y plane and a longitudinal model...

  10. Semiconductor and ceramic microstructure made by single mode fiber laser

    International Nuclear Information System (INIS)

    Pawlak, R; Tomczyk, M; Walczak, M; Domagalski, P

    2014-01-01

    In the paper the results of micromachining of 3D microstructures of microsystems made from silicon and alumina ceramic using a single mode fiber laser (1064 nm) are presented. The quality of obtained structures and its smallest dimensions with acceptable maintained quality were examined. The influence of variable parameters of laser processing with changing of mapping scale on geometrical features of structures was identified.

  11. Interband optical pulse injection locking of quantum dot mode-locked semiconductor laser.

    Science.gov (United States)

    Kim, Jimyung; Delfyett, Peter J

    2008-07-21

    We experimentally demonstrate optical clock recovery from quantum dot mode-locked semiconductor lasers by interband optical pulse injection locking. The passively mode-locked slave laser oscillating on the ground state or the first excited state transition is locked through the injection of optical pulses generated via the opposite transition bands, i.e. the first excited state or the ground state transition from the hybridly mode-locked master laser, respectively. When an optical pulse train generated via the first excited state from the master laser is injected to the slave laser oscillating via ground state, the slave laser shows an asymmetric locking bandwidth around the nominal repetition rate of the slave laser. In the reverse injection case of, i.e. the ground state (master laser) to the first excited state (slave laser), the slave laser does not lock even though both lasers oscillate at the same cavity frequency. In this case, the slave laser only locks to higher injection rates as compared to its own nominal repetition rate, and also shows a large locking bandwidth of 6.7 MHz.

  12. Vibration-tolerant narrow-linewidth semiconductor disk laser using novel frequency-stabilisation schemes

    Science.gov (United States)

    Hunter, Craig R.; Jones, Brynmor E.; Schlosser, Peter; Sørensen, Simon Toft; Strain, Michael J.; McKnight, Loyd J.

    2018-02-01

    This paper will present developments in narrow-linewidth semiconductor-disk-laser systems using novel frequencystabilisation schemes for reduced sensitivity to mechanical vibrations, a critical requirement for mobile applications. Narrow-linewidth single-frequency lasers are required for a range of applications including metrology and highresolution spectroscopy. Stabilisation of the laser was achieved using a monolithic fibre-optic ring resonator with free spectral range of 181 MHz and finesse of 52 to act as passive reference cavity for the laser. Such a cavity can operate over a broad wavelength range and is immune to a wide band of vibrational frequency noise due to its monolithic implementation. The frequency noise of the locked system has been measured and compared to typical Fabry-Perotlocked lasers using vibration equipment to simulate harsh environments, and analysed here. Locked linewidths of portable, narrow-linewidth laser system for harsh environments that can be flexibly designed for a range of applications.

  13. Ultra-Fast All-Optical Self-Aware Protection Switching Based on a Bistable Laser Diode

    DEFF Research Database (Denmark)

    An, Yi; Vukovic, Dragana; Lorences Riesgo, Abel

    2014-01-01

    We propose a novel concept of all-optical protection switching with link failure automatic awareness based on AOWFF. The scheme is experimentally demonstrated using a single MG-Y laser diode with a record switching time ~200 ps....

  14. Semiconductor laser irradiation improves root canal sealing during routine root canal therapy

    Science.gov (United States)

    Hu, Xingxue; Wang, Dashan; Cui, Ting; Yao, Ruyong

    2017-01-01

    Objective To evaluate the effect of semiconductor laser irradiation on root canal sealing after routine root canal therapy (RCT). Methods Sixty freshly extracted single-rooted human teeth were randomly divided into six groups (n = 10). The anatomic crowns were sectioned at the cementoenamel junction and the remaining roots were prepared endodontically with conventional RCT methods. Groups A and B were irradiated with semiconductor laser at 1W for 20 seconds; Groups C and D were ultrasonically rinsed for 60 seconds as positive control groups; Groups E and F without treatment of root canal prior to RCT as negative control groups. Root canal sealing of Groups A, C and E were evaluated by measurements of apical microleakage. The teeth from Groups B, D and F were sectioned, and the micro-structures were examined with scanning electron microscopy (SEM). One way ANOVA and LSD-t test were used for statistical analysis (α = .05). Results The apical sealing of both the laser irradiated group and the ultrasonic irrigated group were significantly different from the control group (pirrigated group (p>0.5). SEM observation showed that most of the dentinal tubules in the laser irradiation group melted, narrowed or closed, while most of the dentinal tubules in the ultrasonic irrigation group were filled with tooth paste. Conclusion The application of semiconductor laser prior to root canal obturation increases the apical sealing of the roots treated. PMID:28957407

  15. A photonic ultra-wideband pulse generator based on relaxation oscillations of a semiconductor laser

    DEFF Research Database (Denmark)

    Yu, Xianbin; Gibbon, Timothy Braidwood; Pawlik, Michal

    2009-01-01

    A photonic ultra-wideband (UWB) pulse generator based on relaxation oscillations of a semiconductor laser is proposed and experimentally demonstrated. We numerically simulate the modulation response of a direct modulation laser (DML) and show that due to the relaxation oscillations of the laser......, the generated signals with complex shape in time domain match the Federal Communications Commission (FCC) mask in the frequency domain. Experimental results using a DML agree well with simulation predictions. Furthermore, we also experimentally demonstrate the generation of FCC compliant UWB signals...

  16. Nanoimprinted organic semiconductor laser pumped by a light-emitting diode.

    Science.gov (United States)

    Tsiminis, Georgios; Wang, Yue; Kanibolotsky, Alexander L; Inigo, Anto R; Skabara, Peter J; Samuel, Ifor D W; Turnbull, Graham A

    2013-05-28

    An organic semiconductor laser, simply fabricated by UV-nanoimprint lithography (UV-NIL), that is pumped with a pulsed InGaN LED is demonstrated. Molecular weight optimization of the polymer gain medium on a nanoimprinted polymer distributed feedback resonator enables the lowest reported UV-NIL laser threshold density of 770 W cm(-2) , establishing the potential for scalable organic laser fabrication compatible with mass-produced LEDs. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Compact 2050 nm Semiconductor Diode Laser Master Oscillator, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase I effort seeks to develop DFB laser master oscillators at the novel wavelength of 12050 nm. Two prototypes will be built, tested, and delivered ....

  18. The theory of laser annealing of disordered semiconductors

    International Nuclear Information System (INIS)

    Noga, M.

    1980-01-01

    A theoretical explanation of the disorder-order phase transition concerning the ion implanted Si pulsed laser annealing is given. The phase transition is related to the Bose condensation of electron-hole plasmons. (author)

  19. Application of laser spot cutting on spring contact probe for semiconductor package inspection

    Science.gov (United States)

    Lee, Dongkyoung; Cho, Jungdon; Kim, Chan Ho; Lee, Seung Hwan

    2017-12-01

    A packaged semiconductor has to be electrically tested to make sure they are free of any manufacturing defects. The test interface, typically employed between a Printed Circuit Board and the semiconductor devices, consists of densely populated Spring Contact Probe (SCP). A standard SCP typically consists of a plunger, a barrel, and an internal spring. Among these components, plungers are manufactured by a stamping process. After stamping, plunger connecting arms need to be cut into pieces. Currently, mechanical cutting has been used. However, it may damage to the body of plungers due to the mechanical force engaged at the cutting point. Therefore, laser spot cutting is considered to solve this problem. The plunger arm is in the shape of a rectangular beam, 50 μm (H) × 90 μm (W). The plunger material used for this research is gold coated beryllium copper. Laser parameters, such as power and elapsed time, have been selected to study laser spot cutting. Laser material interaction characteristics such as a crater size, material removal zone, ablation depth, ablation threshold, and full penetration are observed. Furthermore, a carefully chosen laser parameter (Etotal = 1000mJ) to test feasibility of laser spot cutting are applied. The result show that laser spot cutting can be applied to cut SCP.

  20. Threshold reduction through photon recycling in semiconductor lasers

    Energy Technology Data Exchange (ETDEWEB)

    Gigase, Y.B.; Harder, C.S.; Kesler, M.P.; Meier, H.P. (IBM Research Division, Zurich Research Laboratory, CH-8803 Rueschlikon (Switzerland)); Van Zeghbroeck, B. (University of Colorado, Boulder, CO (USA))

    1990-09-24

    The threshold pump power of an AlGaAs-GaAs ridge quantum well laser diode has been reduced by 42% by recycling the spontaneous emission. An integrated photodiode absorbs the spontaneous radiation emitted by the laser diode and converts it back into electrical power. The recycling of this power results in a reduction of the electrical power required to reach the lasing threshold.

  1. Fabrication of metal/semiconductor nanocomposites by selective laser nano-welding.

    Science.gov (United States)

    Yu, Huiwu; Li, Xiangyou; Hao, Zhongqi; Xiong, Wei; Guo, Lianbo; Lu, Yongfeng; Yi, Rongxing; Li, Jiaming; Yang, Xinyan; Zeng, Xiaoyan

    2017-06-01

    A green and simple method to prepare metal/semiconductor nanocomposites by selective laser nano-welding metal and semiconductor nanoparticles was presented, in which the sizes, phases, and morphologies of the components can be maintained. Many types of nanocomposites (such as Ag/TiO 2 , Ag/SnO 2 , Ag/ZnO 2 , Pt/TiO 2 , Pt/SnO 2 , and Pt/ZnO) can be prepared by this method and their corresponding performances were enhanced.

  2. Pump spot size dependent lasing threshold in organic semiconductor DFB lasers fabricated via nanograting transfer.

    Science.gov (United States)

    Liu, Xin; Klinkhammer, Sönke; Wang, Ziyao; Wienhold, Tobias; Vannahme, Christoph; Jakobs, Peter-Jürgen; Bacher, Andreas; Muslija, Alban; Mappes, Timo; Lemmer, Uli

    2013-11-18

    Optically excited organic semiconductor distributed feedback (DFB) lasers enable efficient lasing in the visible spectrum. Here, we report on the rapid and parallel fabrication of DFB lasers via transferring a nanograting structure from a flexible mold onto an unstructured film of the organic gain material. This geometrically well-defined structure allows for a systematic investigation of the laser threshold behavior. The laser thresholds for these devices show a strong dependence on the pump spot diameter. This experimental finding is in good qualitative agreement with calculations based on coupled-wave theory. With further investigations on various DFB laser geometries prepared by different routes and based on different organic gain materials, we found that these findings are quite general. This is important for the comparison of threshold values of various devices characterized under different excitation areas.

  3. Pump spot size dependent lasing threshold in organic semiconductor DFB lasers fabricated via nanograting transfer

    DEFF Research Database (Denmark)

    Liu, Xin; Klinkhammer, Sönke; Wang, Ziyao

    2013-01-01

    material. This geometrically well-defined structure allows for a systematic investigation of the laser threshold behavior. The laser thresholds for these devices show a strong dependence on the pump spot diameter. This experimental finding is in good qualitative agreement with calculations based on coupled......Optically excited organic semiconductor distributed feedback (DFB) lasers enable efficient lasing in the visible spectrum. Here, we report on the rapid and parallel fabrication of DFB lasers via transferring a nanograting structure from a flexible mold onto an unstructured film of the organic gain......-wave theory. With further investigations on various DFB laser geometries prepared by different routes and based on different organic gain materials, we found that these findings are quite general. This is important for the comparison of threshold values of various devices characterized under different...

  4. Mode structure of delay-coupled semiconductor lasers: influence of the pump current

    International Nuclear Information System (INIS)

    Erzgraeber, Hartmut; Krauskopf, Bernd; Lenstra, Daan

    2005-01-01

    We consider two identical, mutually delay-coupled semiconductor lasers and show that their compound laser modes (CLMs)-the basic continuous wave solutions-depend rather sensitively on the pump current of the lasers. Specifically, we show with figures and accompanying animations how the underlying CLM structure and the associated locking region, where both lasers operate stably with the same frequency, change as a function of the pump current. Our results provide a natural transition between rather different CLM structures that have been reported in the literature. Moreover, we demonstrate how the locking region as well as the different types of instabilities at its boundary depend on the pump current. This is of fundamental interest for the dynamics of coupled lasers and their possible application

  5. Homogeneous spectral spanning of terahertz semiconductor lasers with radio frequency modulation.

    Science.gov (United States)

    Wan, W J; Li, H; Zhou, T; Cao, J C

    2017-03-08

    Homogeneous broadband and electrically pumped semiconductor radiation sources emitting in the terahertz regime are highly desirable for various applications, including spectroscopy, chemical sensing, and gas identification. In the frequency range between 1 and 5 THz, unipolar quantum cascade lasers employing electron inter-subband transitions in multiple-quantum-well structures are the most powerful semiconductor light sources. However, these devices are normally characterized by either a narrow emission spectrum due to the narrow gain bandwidth of the inter-subband optical transitions or an inhomogeneous broad terahertz spectrum from lasers with heterogeneous stacks of active regions. Here, we report the demonstration of homogeneous spectral spanning of long-cavity terahertz semiconductor quantum cascade lasers based on a bound-to-continuum and resonant phonon design under radio frequency modulation. At a single drive current, the terahertz spectrum under radio frequency modulation continuously spans 330 GHz (~8% of the central frequency), which is the record for single plasmon waveguide terahertz lasers with a bound-to-continuum design. The homogeneous broadband terahertz sources can be used for spectroscopic applications, i.e., GaAs etalon transmission measurement and ammonia gas identification.

  6. Multiphoton microscopy in every lab: the promise of ultrafast semiconductor disk lasers

    Science.gov (United States)

    Emaury, Florian; Voigt, Fabian F.; Bethge, Philipp; Waldburger, Dominik; Link, Sandro M.; Carta, Stefano; van der Bourg, Alexander; Helmchen, Fritjof; Keller, Ursula

    2017-07-01

    We use an ultrafast diode-pumped semiconductor disk laser (SDL) to demonstrate several applications in multiphoton microscopy. The ultrafast SDL is based on an optically pumped Vertical External Cavity Surface Emitting Laser (VECSEL) passively mode-locked with a semiconductor saturable absorber mirror (SESAM) and generates 170-fs pulses at a center wavelength of 1027 nm with a repetition rate of 1.63 GHz. We demonstrate the suitability of this laser for structural and functional multiphoton in vivo imaging in both Drosophila larvae and mice for a variety of fluorophores (including mKate2, tdTomato, Texas Red, OGB-1, and R-CaMP1.07) and for endogenous second-harmonic generation in muscle cell sarcomeres. We can demonstrate equivalent signal levels compared to a standard 80-MHz Ti:Sapphire laser when we increase the average power by a factor of 4.5 as predicted by theory. In addition, we compare the bleaching properties of both laser systems in fixed Drosophila larvae and find similar bleaching kinetics despite the large difference in pulse repetition rates. Our results highlight the great potential of ultrafast diode-pumped SDLs for creating a cost-efficient and compact alternative light source compared to standard Ti:Sapphire lasers for multiphoton imaging.

  7. The theoretical and numerical models of the novel and fast tunable semiconductor ring laser

    Science.gov (United States)

    Zhu, Jiangbo; Zhang, Junwen; Chi, Nan; Yu, Siyuan

    2011-01-01

    Fast wavelength-tunable semiconductor lasers will be the key components in future optical packet switching networks. Especially, they are of great importance in the optical network nodes: transmitters, optical wavelength-routers, etc. In this paper, a new scheme of a next-generation fast tunable ring laser was given. Tunable lasers in this design have better wavelength tunability compared with others, for they are switched faster in wavelength and simpler to control with the injecting light from an external distributed Bragg-reflector(DBR). Then some discussion of the waveguide material system and coupler design of the ring laser were given. And we also derived the multimode rate equations corresponding to this scheme by analyzing some characteristics of the semiconductor ring cavity, directionality, nonlinear mode competition, optical injection locking, etc. We did MatLab simulation based on the new rate equations to research the process of mode competition and wavelength switching in the laser, and achieved the basic functions of a tunable laser. Finally some discussion of the impact of several key parameters was given.

  8. Fabrication of laser-target components by semiconductor technology

    International Nuclear Information System (INIS)

    Tindall, W.E.

    1979-01-01

    This paper describes the design and fabrication of a unique silicon substrate with which laser-target components can be mass produced. Different sizes and shapes of gold foils from 50 to 3000 microns in diameter and up to 25 microns thick have been produced with this process since 1976

  9. 1-W quasi-cw near-diffraction-limited semiconductor laser pumped optically by a fibre-coupled diode bar

    OpenAIRE

    Dhanjal, S.; Hoogland, S.; Roberts, J.S.; Hayward, R.A.; Clarkson, W.A.; Tropper, Anne

    2000-01-01

    We describe a diode-bar-pumped vertical-external-cavity surface-emitting semiconductor laser, which in quasi-cw operation emitted a peak power of >1 W at 1020 nm in a circular, near diffraction-limited beam.

  10. Ten years optically pumped semiconductor lasers: review, state-of-the-art, and future developments

    Science.gov (United States)

    Kannengiesser, Christian; Ostroumov, Vasiliy; Pfeufer, Volker; Seelert, Wolf; Simon, Christoph; von Elm, Rüdiger; Zuck, Andreas

    2010-02-01

    Optically Pumped Semiconductor Lasers - OPSLs - have been introduced in 2001. Their unique features such as power scalability and wavelength flexibility, their excellent beam parameters, power stability and reliability opened this pioneering technology access to a wide range of applications such as flow cytometry, confocal microscopy, sequencing, medical diagnosis and therapy, semiconductor inspection, graphic arts, forensic, metrology. This talk will introduce the OPSL principles and compare them with ion, diode and standard solid state lasers. It will revue the first 10 years of this exciting technology, its current state and trends. In particular currently accessible wavelengths and power ranges, frequency doubling, ultra-narrow linewidth possibilities will be discussed. A survey of key applications will be given.

  11. N.G. Basov and early works on semiconductor lasers at P.N. Lebedev Physics Institute

    International Nuclear Information System (INIS)

    Eliseev, P G

    2012-01-01

    A survey is presented of works on creation and investigation of semiconductor lasers during 1957 – 1977 at the P.N. Lebedev Physics Institute. Many of these works were initiated by N.G. Basov, starting from pre-laser time, when N.G. Basov and his coworkers formulated principal conditions of creation of lasers on interband transitions in semiconductors. Main directions of further works were diode lasers based on various materials and structures, their characteristics of output power, high-speed operation and reliability. (special issue devoted to the 90th anniversary of n.g. basov)

  12. Picosecond Laser Pulse Interactions with Metallic and Semiconductor Surfaces.

    Science.gov (United States)

    1984-11-01

    thermometric determination of plasma relaxation is by far more sensitive than direct optical measurements. The solid line in Fig. 4 shows the calculated...passively mode-locked Nd:yttrium aluminum garnet in Si, several researchers have used high picosecond or fem- laser was used to produce single 30-ps, 1.06...these targets to an aluminum backing plate with a silver-epoxy conducting glue (Ablestik). The conductivity of the targets was high enough to make

  13. Preparation of ZnS semiconductor nanocrystals using pulsed laser ablation in aqueous surfactant solutions

    International Nuclear Information System (INIS)

    Choi, S-H; Sasaki, T; Shimizu, Y; Yoon, J-W; Nichols, W T; Sung, Y-E; Koshizaki, N

    2007-01-01

    Cubic ZnS semiconductor nanocrystals with the size of 2 to 5 nm were prepared by pulsed laser ablation in aqueous surfactant solutions of sodium dodecyl sulfate and cetyltrimethylammonium bromide without any further treatments. The obtained suspensions of the nanocrystals have broad photoluminescence emission from 375 to 600 nm. The abundance and emission intensity of the nanocrystals depend on the concentration of the surfactant in solution

  14. Dynamics of modal power distribution in a multimode semiconductor laser with optical feedback

    International Nuclear Information System (INIS)

    Buldu, J M; Trull, J; Torrent, M C; GarcIa-Ojalvo, J; Mirasso, Claudio R

    2002-01-01

    The dynamics of power distribution between longitudinal modes of a multimode semiconductor laser subjected to external optical feedback is experimentally analysed in the low-frequency fluctuation regime. Power dropouts in the total light intensity are invariably accompanied by sudden activations of several longitudinal modes. These activations are seen not to be simultaneous to the dropouts, but to occur after them. The phenomenon is statistically analysed in a systematic way, and the corresponding delay is estimated. (letter to the editor)

  15. Dynamics of modal power distribution in a multimode semiconductor laser with optical feedback

    Energy Technology Data Exchange (ETDEWEB)

    Buldu, J M [Departament de FIsica i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Colom 11, E-08222 Terrassa (Spain); Trull, J [Departament de FIsica i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Colom 11, E-08222 Terrassa (Spain); Torrent, M C [Departament de FIsica i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Colom 11, E-08222 Terrassa (Spain); GarcIa-Ojalvo, J [Departament de FIsica i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Colom 11, E-08222 Terrassa (Spain); Mirasso, Claudio R [Departament de FIsica, Universitat de les Illes Balears, E-07071 Palma de Mallorca (Spain)

    2002-02-01

    The dynamics of power distribution between longitudinal modes of a multimode semiconductor laser subjected to external optical feedback is experimentally analysed in the low-frequency fluctuation regime. Power dropouts in the total light intensity are invariably accompanied by sudden activations of several longitudinal modes. These activations are seen not to be simultaneous to the dropouts, but to occur after them. The phenomenon is statistically analysed in a systematic way, and the corresponding delay is estimated. (letter to the editor)

  16. Semiconductor laser joint study program with Rome Laboratory

    Science.gov (United States)

    Schaff, William J.; Okeefe, Sean S.; Eastman, Lester F.

    1994-09-01

    A program to jointly study vertical-cavity surface emitting lasers (VCSEL) for high speed vertical optical interconnects (VOI) has been conducted under an ES&E between Rome Laboratory and Cornell University. Lasers were designed, grown, and fabricated at Cornell University. A VCSEL measurement laboratory has been designed, built, and utilized at Rome Laboratory. High quality VCSEL material was grown and characterized by fabricating conventional lateral cavity lasers that emitted at the design wavelength of 1.04 microns. The VCSEL's emit at 1.06 microns. Threshold currents of 16 mA at 4.8 volts were obtained for 30 microns diameter devices. Output powers of 5 mW were measured. This is 500 times higher power than from the light emitting diodes employed previously for vertical optical interconnects. A new form of compositional grading using a cosinusoidal function has been developed and is very successful for reducing diode series resistance for high speed interconnection applications. A flip-chip diamond package compatible with high speed operation of 16 VCSEL elements has been designed and characterized. A flip-chip device binding effort at Rome Laboratory was also designed and initiated. This report presents details of the one-year effort, including process recipes and results.

  17. Comprehensive experimental analysis of nonlinear dynamics in an optically-injected semiconductor laser

    Directory of Open Access Journals (Sweden)

    Kevin Schires

    2011-09-01

    Full Text Available We present the first comprehensive experimental study, to our knowledge, of the routes between nonlinear dynamics induced in a semiconductor laser under external optical injection based on an analysis of time-averaged measurements of the optical and RF spectra and phasors of real-time series of the laser output. The different means of analysis are compared for several types of routes and the benefits of each are discussed in terms of the identification and mapping of the nonlinear dynamics. Finally, the results are presented in a novel audio/video format that describes the evolution of the dynamics with the injection parameters.

  18. Electroluminescence Analysis by Tilt Polish Technique of InP-Based Semiconductor Lasers

    Science.gov (United States)

    Ichikawa, Hiroyuki; Sasaki, Kouichi; Hamada, Kotaro; Yamaguchi, Akira

    2010-03-01

    We developed an effective electroluminescence (EL) analysis method to specify the degraded region of InP-based semiconductor lasers. The EL analysis method is one of the most important methods for failure analysis. However, EL observation was difficult because opaque electrodes surround an active layer. A portion of each electrode had to be left intact for wiring to inject the current. Thus, we developed a partial polish technique for the bottom electrode. Tilt polish equipment with a rotating table was introduced; a flat polished surface and a sufficiently wide remaining portion of the bottom electrode were obtained. As a result, clear EL from the back surface of the laser was observed.

  19. Stability diagrams for continuous wide-range control of two mutually delay-coupled semiconductor lasers

    International Nuclear Information System (INIS)

    Junges, Leandro; Gallas, Jason A C

    2015-01-01

    The dynamics of two mutually delay-coupled semiconductor lasers has been frequently studied experimentally, numerically, and analytically either for weak or strong detuning between the lasers. Here, we present a systematic numerical investigation spanning all detuning ranges. We report high-resolution stability diagrams for wide ranges of the main control parameters of the laser, as described by the Lang–Kobayashi model. In particular, we detail the parameter influence on dynamical performance and map the distribution of chaotic pulsations and self-generated periodic spiking with arbitrary periodicity. Special attention is given to the unfolding of regular pulse packages for both symmetric and non-symmetric configurations with respect to detuning. The influence of the delay –time on the self-organization of periodic and chaotic laser phases as a function of the coupling and detuning is also described in detail. (paper)

  20. Gigahertz dual-comb modelocked diode-pumped semiconductor and solid-state lasers

    Science.gov (United States)

    Link, S. M.; Mangold, M.; Golling, M.; Klenner, A.; Keller, U.

    2016-03-01

    We present a simple approach to generate simultaneously two gigahertz mode-locked pulse trains from a single gain element. A bi-refringent crystal in the laser cavity splits the one cavity beam into two cross-polarized and spatially separated beams. This polarization-duplexing is successfully demonstrated for both a semiconductor disk laser (i.e. MIXSEL) and a diode-pumped solid-state Nd:YAG laser. The beat between the two beams results in a microwave frequency comb, which represents a direct link between the terahertz optical frequencies and the electronically accessible microwave regime. This dual-output technique enables compact and cost-efficient dual-comb lasers for spectroscopy applications.

  1. Near infrared laser stimulation of human neural stem cells into neurons on graphene nanomesh semiconductors.

    Science.gov (United States)

    Akhavan, Omid; Ghaderi, Elham; Shirazian, Soheil A

    2015-02-01

    Reduced graphene oxide nanomeshes (rGONMs), as p-type semiconductors with band-gap energy of ∼ 1 eV, were developed and applied in near infrared (NIR) laser stimulation of human neural stem cells (hNSCs) into neurons. The biocompatibility of the rGONMs in growth of hNSCs was found similar to that of the graphene oxide (GO) sheets. Proliferation of the hNSCs on the GONMs was assigned to the excess oxygen functional groups formed on edge defects of the GONMs, resulting in superhydrophilicity of the surface. Under NIR laser stimulation, the graphene layers (especially the rGONMs) exhibited significant cell differentiations, including more elongations of the cells and higher differentiation of neurons than glia. The higher hNSC differentiation on the rGONM than the reduced GO (rGO) was assigned to the stimulation effects of the low-energy photoexcited electrons injected from the rGONM semiconductors into the cells, while the high-energy photoelectrons of the rGO (as a zero band-gap semiconductor) could suppress the cell proliferation and/or even cause cell damages. Using conventional heating of the culture media up to ∼ 43 °C (the temperature typically reached under the laser irradiation), no significant differentiation was observed in dark. This further confirmed the role of photoelectrons in the hNSC differentiation. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Dynamics of InGaN tandem blue-violet semiconductor lasers

    International Nuclear Information System (INIS)

    Antohi, I.; Rusu, S.S.; Tronciu, V.Z.

    2013-01-01

    Full text: Blue-violet semiconductor lasers have received much attention because of their promise for high-density optical storage applications. In particular, blue-violet laser diodes operating at 400 nm are required for BD- systems and for use in medicine, biology, color printers and monitors, etc, In recent years, numerous fabrication methods have been proposed and developed for blue lasers with CW and self-pulsating operations and the lifetime of such lasers has been increased to over 15000 h. Recently, we have reported self-pulsation and excitable behaviour for an InGaN laser with a p-type saturable absorber, and SP in the frequency range from 1.6 to 2.9 GHz has been achieved with such lasers. In this paper, we present an investigation of the dynamics of tandem 400 nm blue-violet lasers with setup presented in Fig.1a. A particular feature of the devices is the connection of the contacts of the SA, to reduce the carrier lifetime in the SA with the intention of producing self-pulsation and excitability. We examine the laser dynamics in terms of bifurcation diagrams. A typical calculation of bifurcation for the periodic solution is shown in Fig. 1b. This figure shows the dependence of the peak of the photon number on the injected.

  3. Dilute ferromagnetic semiconductors prepared by the combination of ion implantation with pulse laser melting

    International Nuclear Information System (INIS)

    Zhou, Shengqiang

    2015-01-01

    Combining semiconducting and ferromagnetic properties, dilute ferromagnetic semiconductors (DFS) have been under intensive investigation for more than two decades. Mn doped III–V compound semiconductors have been regarded as the prototype of DFS from both experimental and theoretic investigations. The magnetic properties of III–V:Mn can be controlled by manipulating free carriers via electrical gating, as for controlling the electrical properties in conventional semiconductors. However, the preparation of DFS presents a big challenge due to the low solubility of Mn in semiconductors. Ion implantation followed by pulsed laser melting (II-PLM) provides an alternative to the widely used low-temperature molecular beam epitaxy (LT-MBE) approach. Both ion implantation and pulsed-laser melting occur far enough from thermodynamic equilibrium conditions. Ion implantation introduces enough dopants and the subsequent laser pulse deposit energy in the near-surface region to drive a rapid liquid-phase epitaxial growth. Here, we review the experimental study on preparation of III–V:Mn using II-PLM. We start with a brief description about the development of DFS and the physics behind II-PLM. Then we show that ferromagnetic GaMnAs and InMnAs films can be prepared by II-PLM and they show the same characteristics of LT-MBE grown samples. Going beyond LT-MBE, II-PLM is successful to bring two new members, GaMnP and InMnP, into the family of III–V:Mn DFS. Both GaMnP and InMnP films show the signature of DFS and an insulating behavior. At the end, we summarize the work done for Ge:Mn and Si:Mn using II-PLM and present suggestions for future investigations. The remarkable advantage of II-PLM approach is its versatility. In general, II-PLM can be utilized to prepare supersaturated alloys with mismatched components. (topical review)

  4. Micromachining of semiconductor by femtosecond laser for integrated circuit defect analysis

    International Nuclear Information System (INIS)

    Halbwax, M.; Sarnet, T.; Hermann, J.; Delaporte, Ph.; Sentis, M.; Fares, L.; Haller, G.

    2007-01-01

    The latest International Technology Roadmap for Semiconductors (ITRS) has highlighted the detection and analysis of defects in Integrated Circuits (IC) as a major challenge faced by the semiconductor industry. Advanced tools used today for defect cross sectioning include dual beams (focused ion- and electron-beam technologies) with resolution down to the sub-Angstrom level. However ion milling an IC with a FIB is time consuming because of the need to open wide cavities in front of the cross-sections that need to be analyzed. Therefore the use of a femtosecond laser as a tool for direct material removal is discussed in this paper. Experiments were performed on IC structures to reveal the different layers of fabrication: selective or total ablation can occur depending on the laser energy density, without delamination of the layers. Different laser irradiation conditions like pressure (air, vacuum), polarization, beam shaping, and scanning parameters have been used to produce different types of cavities. The femtosecond laser engraving of silicon-based structures could be useful for cross-sectioning devices but also for other applications like direct-write lithography, photomask repair, maskless implantation or reverse engineering/restructuring

  5. Micromachining of semiconductor by femtosecond laser for integrated circuit defect analysis

    Energy Technology Data Exchange (ETDEWEB)

    Halbwax, M. [Laboratoire LP3 CNRS UMR 6182, Parc Scientifique et Technologique de Luminy, Case 917, 163 Avenue de Luminy, 13009 Marseille (France); Sarnet, T. [Laboratoire LP3 CNRS UMR 6182, Parc Scientifique et Technologique de Luminy, Case 917, 163 Avenue de Luminy, 13009 Marseille (France)], E-mail: sarnet@lp3.univ-mrs.fr; Hermann, J.; Delaporte, Ph.; Sentis, M. [Laboratoire LP3 CNRS UMR 6182, Parc Scientifique et Technologique de Luminy, Case 917, 163 Avenue de Luminy, 13009 Marseille (France); Fares, L.; Haller, G. [STMicroelectronics, 190 Avenue Celestin Coq, ZI, 13106 Rousset Cedex (France)

    2007-12-15

    The latest International Technology Roadmap for Semiconductors (ITRS) has highlighted the detection and analysis of defects in Integrated Circuits (IC) as a major challenge faced by the semiconductor industry. Advanced tools used today for defect cross sectioning include dual beams (focused ion- and electron-beam technologies) with resolution down to the sub-Angstrom level. However ion milling an IC with a FIB is time consuming because of the need to open wide cavities in front of the cross-sections that need to be analyzed. Therefore the use of a femtosecond laser as a tool for direct material removal is discussed in this paper. Experiments were performed on IC structures to reveal the different layers of fabrication: selective or total ablation can occur depending on the laser energy density, without delamination of the layers. Different laser irradiation conditions like pressure (air, vacuum), polarization, beam shaping, and scanning parameters have been used to produce different types of cavities. The femtosecond laser engraving of silicon-based structures could be useful for cross-sectioning devices but also for other applications like direct-write lithography, photomask repair, maskless implantation or reverse engineering/restructuring.

  6. Laser photo-reflectance characterization of resonant nonlinear electro-refraction in thin semiconductor films

    International Nuclear Information System (INIS)

    Chism, Will; Cartwright, Jason

    2012-01-01

    Photo-reflectance (PR) measurements provide a non-contact means for the precise characterization of semiconductor electronic properties. In this paper, we investigate the use of a laser beam as the probe beam in the PR setup. In this case it is seen that the nonlinear refraction is responsible for the amplitude change of the reflected probe field, whereas the phase change is due to nonlinear absorption. The open aperture condition may then be used to eliminate the spatial phase at the detector, thereby isolating the electro-refractive contribution to the PR signal. This greatly simplifies the PR analysis and allows absolute measurements of electro-refraction in thin semiconductor films. We report the application of the laser PR technique to characterize physical strain in thin silicon on silicon-germanium films. - Highlights: ► We describe the theory of laser photoreflectance. ► Laser photoreflectance is used to independently characterize nonlinear refraction. ► We report the characterization of strain in thin strained silicon films.

  7. Improved performance of high average power semiconductor arrays for applications in diode pumped solid state lasers

    International Nuclear Information System (INIS)

    Beach, R.; Emanuel, M.; Benett, W.; Freitas, B.; Ciarlo, D.; Carlson, N.; Sutton, S.; Skidmore, J.; Solarz, R.

    1994-01-01

    The average power performance capability of semiconductor diode laser arrays has improved dramatically over the past several years. These performance improvements, combined with cost reductions pursued by LLNL and others in the fabrication and packaging of diode lasers, have continued to reduce the price per average watt of laser diode radiation. Presently, we are at the point where the manufacturers of commercial high average power solid state laser systems used in material processing applications can now seriously consider the replacement of their flashlamp pumps with laser diode pump sources. Additionally, a low cost technique developed and demonstrated at LLNL for optically conditioning the output radiation of diode laser arrays has enabled a new and scalable average power diode-end-pumping architecture that can be simply implemented in diode pumped solid state laser systems (DPSSL's). This development allows the high average power DPSSL designer to look beyond the Nd ion for the first time. Along with high average power DPSSL's which are appropriate for material processing applications, low and intermediate average power DPSSL's are now realizable at low enough costs to be attractive for use in many medical, electronic, and lithographic applications

  8. Semiconductor optical amplifier-based heterodyning detection for resolving optical terahertz beat-tone signals from passively mode-locked semiconductor lasers

    International Nuclear Information System (INIS)

    Latkowski, Sylwester; Maldonado-Basilio, Ramon; Carney, Kevin; Parra-Cetina, Josue; Philippe, Severine; Landais, Pascal

    2010-01-01

    An all-optical heterodyne approach based on a room-temperature controlled semiconductor optical amplifier (SOA) for measuring the frequency and linewidth of the terahertz beat-tone signal from a passively mode-locked laser is proposed. Under the injection of two external cavity lasers, the SOA acts as a local oscillator at their detuning frequency and also as an optical frequency mixer whose inputs are the self-modulated spectrum of the device under test and the two laser beams. Frequency and linewidth of the intermediate frequency signal (and therefore, the beat-tone signal) are resolved by using a photodiode and an electrical spectrum analyzer.

  9. Frequency response control of semiconductor laser by using hybrid modulation scheme.

    Science.gov (United States)

    Mieda, Shigeru; Yokota, Nobuhide; Isshiki, Ryuto; Kobayashi, Wataru; Yasaka, Hiroshi

    2016-10-31

    A hybrid modulation scheme that simultaneously applies the direct current modulation and intra-cavity loss modulation to a semiconductor laser is proposed. Both numerical calculations using rate equations and experiments using a fabricated laser show that the hybrid modulation scheme can control the frequency response of the laser by changing a modulation ratio and time delay between the two modulations. The modulation ratio and time delay provide the degree of signal mixing of the two modulations and an optimum condition is found when a non-flat frequency response for the intra-cavity loss modulation is compensated by that for the direct current modulation. We experimentally confirm a 8.64-dB improvement of the modulation sensitivity at 20 GHz compared with the pure direct current modulation with a 0.7-dB relaxation oscillation peak.

  10. High-order diffraction gratings for high-power semiconductor lasers

    International Nuclear Information System (INIS)

    Vasil’eva, V. V.; Vinokurov, D. A.; Zolotarev, V. V.; Leshko, A. Yu.; Petrunov, A. N.; Pikhtin, N. A.; Rastegaeva, M. G.; Sokolova, Z. N.; Shashkin, I. S.; Tarasov, I. S.

    2012-01-01

    A deep diffraction grating with a large period (∼2 μm) within one of the cladding layers is proposed for the implementation of selective feedback in a semiconductor laser. Frequency dependences of reflectance in the 12th diffraction order for rectangular, triangular, and trapezoidal diffraction gratings are calculated. It is shown that the maximum reflectance of the waveguide mode is attained using a rectangular or trapezoidal grating ∼2 μm deep in the laser structure. Deep trapezoidal diffraction gratings with large periods are fabricated in the Al 0.3 Ga 0.7 As cladding layer of a GaAs/AlGaAs laser structure using photolithography and reactive ion etching.

  11. Optical-feedback semiconductor laser Michelson interferometer for displacement measurements with directional discrimination

    International Nuclear Information System (INIS)

    Rodrigo, Peter John; Lim, May; Saloma, Caesar

    2001-01-01

    An optical-feedback semiconductor laser Michelson interferometer (OSMI) is presented for measuring microscopic linear displacements without ambiguity in the direction of motion. The two waves from the interferometer arms, one from the reference mirror and the other from the reflecting moving target, are fed back into the lasing medium (λ=830 nm), causing variations in the laser output power. We model the OSMI into an equivalent Fabry-Perot resonator and derive the dependence of the output power (and the junction voltage) on the path difference between the two interferometer arms. Numerical and experimental results consistently show that the laser output power varies periodically (period, λ/2) with path difference. The output power variation exhibits an asymmetric behavior with the direction of motion, which is used to measure, at subwavelength resolution, the displacement vector (both amplitude and direction) of the moving sample. Two samples are considered in the experiments: (i) a piezoelectric transducer and (ii) an audio speaker

  12. TE-TM dynamics in a semiconductor laser subject to polarization-rotated optical feedback

    International Nuclear Information System (INIS)

    Heil, T.; Uchida, A.; Davis, P.; Aida, T.

    2003-01-01

    We present a comprehensive experimental characterization of the dynamics of semiconductor lasers subject to polarization-rotated optical feedback. We find oscillatory instabilities appearing for large feedback levels and disappearing at large injection currents, which we classify in contrast to the well-known conventional optical-feedback-induced dynamics. In addition, we compare our experiments to theoretical results of a single-mode model assuming incoherence of the optical feedback, and we identify differences concerning the average power of the laser. Hence, we develop an alternative model accounting for both polarizations, where the emission of the dominant TE mode is injected with delay into the TM mode of the laser. Numerical simulations using this model show good qualitative agreement with our experimental results, correctly reproducing the parameter dependences of the dynamics. Finally, we discuss the application of polarization-rotated-feedback induced instabilities in chaotic carrier communication systems

  13. Conversion from non-orthogonally to orthogonally polarized optical single-sideband modulation using optically injected semiconductor lasers.

    Science.gov (United States)

    Hung, Yu-Han; Tseng, Chin-Hao; Hwang, Sheng-Kwang

    2018-06-01

    This Letter investigates an optically injected semiconductor laser for conversion from non-orthogonally to orthogonally polarized optical single-sideband modulation. The underlying mechanism relies solely on nonlinear laser characteristics and, thus, only a typical semiconductor laser is required as the key conversion unit. This conversion can be achieved for a broadly tunable frequency range up to at least 65 GHz. After conversion, the microwave phase quality, including linewidth and phase noise, is mostly preserved, and simultaneous microwave amplification up to 23 dB is feasible.

  14. Observation of modulation speed enhancement, frequency modulation suppression, and phase noise reduction by detuned loading in a coupled-cavity semiconductor laser

    OpenAIRE

    Vahala, Kerry; Paslaski, Joel; Yariv, Amnon

    1985-01-01

    Simultaneous direct modulation response enhancement, phase noise (linewidth) reduction, and frequency modulation suppression are produced in a coupled-cavity semiconductor laser by the detuned loading mechanism.

  15. Stimulated Brillouin scattering of laser in semiconductor plasma embedded with nano-sized grains

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Giriraj, E-mail: grsharma@gmail.com [SRJ Government Girls’ College, Neemuch (M P) (India); Dad, R. C. [Government P G College, Mandsaur (M P) (India); Ghosh, S. [School of Studies in Physics, Vikram University, Ujjain, (M P) (India)

    2015-07-31

    A high power laser propagating through semiconductor plasma undergoes Stimulated Brillouin scattering (SBS) from the electrostrictively generated acoustic perturbations. We have considered that nano-sized grains (NSGs) ions are embedded in semiconductor plasma by means of ion implantation. The NSGs are bombarded by the surrounding plasma particles and collect electrons. By considering a negative charge on the NSGs, we present an analytically study on the effects of NSGs on threshold field for the onset of SBS and Brillouin gain of generated Brillouin scattered mode. It is found that as the charge on the NSGs builds up, the Brillouin gain is significantly raised and the threshold pump field for the onset of SBS process is lowered.

  16. Multipulse dynamics of a passively mode-locked semiconductor laser with delayed optical feedback

    Science.gov (United States)

    Jaurigue, Lina; Krauskopf, Bernd; Lüdge, Kathy

    2017-11-01

    Passively mode-locked semiconductor lasers are compact, inexpensive sources of short light pulses of high repetition rates. In this work, we investigate the dynamics and bifurcations arising in such a device under the influence of time delayed optical feedback. This laser system is modelled by a system of delay differential equations, which includes delay terms associated with the laser cavity and feedback loop. We make use of specialised path continuation software for delay differential equations to analyse the regime of short feedback delays. Specifically, we consider how the dynamics and bifurcations depend on the pump current of the laser, the feedback strength, and the feedback delay time. We show that an important role is played by resonances between the mode-locking frequencies and the feedback delay time. We find feedback-induced harmonic mode locking and show that a mismatch between the fundamental frequency of the laser and that of the feedback cavity can lead to multi-pulse or quasiperiodic dynamics. The quasiperiodic dynamics exhibit a slow modulation, on the time scale of the gain recovery rate, which results from a beating with the frequency introduced in the associated torus bifurcations and leads to gain competition between multiple pulse trains within the laser cavity. Our results also have implications for the case of large feedback delay times, where a complete bifurcation analysis is not practical. Namely, for increasing delay, there is an ever-increasing degree of multistability between mode-locked solutions due to the frequency pulling effect.

  17. Optoelectronic integrated circuits utilising vertical-cavity surface-emitting semiconductor lasers

    International Nuclear Information System (INIS)

    Zakharov, S D; Fyodorov, V B; Tsvetkov, V V

    1999-01-01

    Optoelectronic integrated circuits with additional optical inputs/outputs, in which vertical-cavity surface-emitting (VCSE) lasers perform the data transfer functions, are considered. The mutual relationship and the 'affinity' between optical means for data transfer and processing, on the one hand, and the traditional electronic component base, on the other, are demonstrated in the case of implementation of three-dimensional interconnects with a high transmission capacity. Attention is drawn to the problems encountered when semiconductor injection lasers are used in communication lines. It is shown what role can be played by VCSE lasers in solving these problems. A detailed analysis is made of the topics relating to possible structural and technological solutions in the fabrication of single lasers and of their arrays, and also of the problems hindering integrating of lasers into emitter arrays. Considerable attention is given to integrated circuits with optoelectronic smart pixels. Various technological methods for vertical integration of GaAs VCSE lasers with the silicon substrate of a microcircuit (chip) are discussed. (review)

  18. Theoretical modeling of the dynamics of a semiconductor laser subject to double-reflector optical feedback

    Energy Technology Data Exchange (ETDEWEB)

    Bakry, A. [King Abdulaziz University, 80203, Department of Physics, Faculty of Science (Saudi Arabia); Abdulrhmann, S. [Jazan University, 114, Department of Physics, Faculty of Sciences (Saudi Arabia); Ahmed, M., E-mail: mostafa.farghal@mu.edu.eg [King Abdulaziz University, 80203, Department of Physics, Faculty of Science (Saudi Arabia)

    2016-06-15

    We theoretically model the dynamics of semiconductor lasers subject to the double-reflector feedback. The proposed model is a new modification of the time-delay rate equations of semiconductor lasers under the optical feedback to account for this type of the double-reflector feedback. We examine the influence of adding the second reflector to dynamical states induced by the single-reflector feedback: periodic oscillations, period doubling, and chaos. Regimes of both short and long external cavities are considered. The present analyses are done using the bifurcation diagram, temporal trajectory, phase portrait, and fast Fourier transform of the laser intensity. We show that adding the second reflector attracts the periodic and perioddoubling oscillations, and chaos induced by the first reflector to a route-to-continuous-wave operation. During this operation, the periodic-oscillation frequency increases with strengthening the optical feedback. We show that the chaos induced by the double-reflector feedback is more irregular than that induced by the single-reflector feedback. The power spectrum of this chaos state does not reflect information on the geometry of the optical system, which then has potential for use in chaotic (secure) optical data encryption.

  19. Ring-shaped active mode-locked tunable laser using quantum-dot semiconductor optical amplifier

    Science.gov (United States)

    Zhang, Mingxiao; Wang, Yongjun; Liu, Xinyu

    2018-03-01

    In this paper, a lot of simulations has been done for ring-shaped active mode-locked lasers with quantum-dot semiconductor optical amplifier (QD-SOA). Based on the simulation model of QD-SOA, we discussed about the influence towards mode-locked waveform frequency and pulse caused by QD-SOA maximum mode peak gain, active layer loss coefficient, bias current, incident light pulse, fiber nonlinear coefficient. In the meantime, we also take the tunable performance of the laser into consideration. Results showed QD-SOA a better performance than original semiconductor optical amplifier (SOA) in recovery time, line width, and nonlinear coefficients, which makes it possible to output a locked-mode impulse that has a higher impulse power, narrower impulse width as well as the phase is more easily controlled. After a lot of simulations, this laser can realize a 20GHz better locked-mode output pulse after 200 loops, where the power is above 17.5mW, impulse width is less than 2.7ps, moreover, the tunable wavelength range is between 1540nm-1580nm.

  20. Packaged semiconductor laser optical phase locked loop for photonic generation, processing and transmission of microwave signals

    DEFF Research Database (Denmark)

    Langley, L.N.; Elkin, M.D.; Edege, C.

    1999-01-01

    In this paper, we present the first fully packaged semiconductor laser optical phase-locked loop (OPLL) microwave photonic transmitter. The transmitter is based on semiconductor lasers that are directly phase locked without the use of any other phase noise-reduction mechanisms. In this transmitter......, the lasers have a free-running summed linewidth of 6 MHz and the OPLL has a feedback bandwidth of 70 MHz, A state-of-the-art performance is obtained, with a total phase-error variance of 0.05 rad(2) (1-GHz bandwidth) and a carrier phase-error variance of 7x10(-4) rad(2) in a 15-MHz bandwidth. Carriers...... are generated in the range of 7-14 GHz. The OPLL transmitter has been fully packaged for practical use in field trials. This is the first time this type of transmitter has been fabricated in a packaged state which is a significant advance on the route to practical application....

  1. Effect of Suyuping combined with semiconductor laser irradiation on wound healing after anal fistula surgery

    Institute of Scientific and Technical Information of China (English)

    Min Zhao; Chang-Ye Sang; Zhen-Jun Wang; Yan-Chun Xu

    2016-01-01

    Objective:To explore the effect of Suyuping combined with semiconductor laser irradiation on the wound healing after anal fistula surgery.Methods:A total of 180 patients with anal fistula who were admitted in our hospital from October, 2013 to May, 2015 for surgery were included in the study and randomized into the treatment group and the control group with 90 cases in each group. The patients in the control group were given the conventional surgical debridement dressing, a time a day. On this basis, the patients in the treatment group were given Suyuping smearing on the wound sinus tract combined with semiconductor laser irradiation, a time a day for 10 min, continuous irradiation until wound healing. The postoperative wound swelling fading, wound surface secretion amount, and the clinical efficacy in the two groups were recorded.Results:The wound surface swelling degree and wound pain degree at each timing point after operation in the treatment group were significantly lower than those in the control group (P<0.05). The wound surface area at each timing point after operation in the treatment group was significantly lower than that in the control group (P<0.05). The wound surface secretion amount 6, 9, and 12 days after operation in the treatment group was significantly lower than that in the control group (P<0.05). The total effective rate in the treatment group was significantly higher than that in the control group (P<0.05). The average healing time in the treatment group was significantly faster than that in the control group (P<0.05). Conclusions: Suyuping combined with semiconductor laser irradiation in the treatment of patients after anal fistula can effectively improve the local blood and lymphatic circulation of wound surface, promote the growth of granulation tissues, and contribute the wound healing.

  2. Effect of Suyuping combined with semiconductor laser irradiation on wound healing after anal fistula surgery

    Directory of Open Access Journals (Sweden)

    Min Zhao

    2016-06-01

    Full Text Available Objective: To explore the effect of Suyuping combined with semiconductor laser irradiation on the wound healing after anal fistula surgery. Methods: A total of 180 patients with anal fistula who were admitted in our hospital from October, 2013 to May, 2015 for surgery were included in the study and randomized into the treatment group and the control group with 90 cases in each group. The patients in the control group were given the conventional surgical debridement dressing, a time a day. On this basis, the patients in the treatment group were given Suyuping smearing on the wound sinus tract combined with semiconductor laser irradiation, a time a day for 10 min, continuous irradiation until wound healing. The postoperative wound swelling fading, wound surface secretion amount, and the clinical efficacy in the two groups were recorded. Results: The wound surface swelling degree and wound pain degree at each timing point after operation in the treatment group were significantly lower than those in the control group (P<0.05. The wound surface area at each timing point after operation in the treatment group was significantly lower than that in the control group (P<0.05. The wound surface secretion amount 6, 9, and 12 days after operation in the treatment group was significantly lower than that in the control group (P<0.05. The total effective rate in the treatment group was significantly higher than that in the control group (P<0.05. The average healing time in the treatment group was significantly faster than that in the control group (P<0.05. Conclusions: Suyuping combined with semiconductor laser irradiation in the treatment of patients after anal fistula can effectively improve the local blood and lymphatic circulation of wound surface, promote the growth of granulation tissues, and contribute the wound healing.

  3. Crisis route to chaos in semiconductor lasers subjected to external optical feedback

    Science.gov (United States)

    Wishon, Michael J.; Locquet, Alexandre; Chang, C. Y.; Choi, D.; Citrin, D. S.

    2018-03-01

    Semiconductor lasers subjected to optical feedback have been intensively used as archetypical testbeds for high-speed (sub-ns) and high-dimensional nonlinear dynamics. By simultaneously extracting all the dynamical variables, we demonstrate that for larger current, the commonly named "quasiperiodic" route is in fact based on mixed external-cavity solutions that lock the oscillation frequency of the intensity, voltage, and separation in optical frequency through a mechanism involving successive rejections along the unstable manifold of an antimode. We show that chaos emerges from a crisis resulting from the inability to maintain locking as the unstable manifold becomes inaccessible.

  4. Field performance of an all-semiconductor laser coherent Doppler lidar

    DEFF Research Database (Denmark)

    Rodrigo, Peter John; Pedersen, Christian

    2012-01-01

    We implement and test what, to our knowledge, is the first deployable coherent Doppler lidar (CDL) system based on a compact, inexpensive all-semiconductor laser (SL). To demonstrate the field performance of our SL-CDL remote sensor, we compare a 36 h time series of averaged radial wind speeds...... measured by our instrument at an 80 m distance to those simultaneously obtained from an industry-standard sonic anemometer (SA). An excellent degree of correlation (R2=0.994 and slope=0.996) is achieved from a linear regression analysis of the CDL versus SA wind speed data. The lidar system is capable...

  5. Analysis of timing jitter in external-cavity mode-locked semiconductor lasers

    DEFF Research Database (Denmark)

    Mulet, Josep; Mørk, Jesper

    2006-01-01

    We develop a comprehensive theoretical description of passive mode-locking in external-cavity mode-locked semiconductor lasers based on a fully distributed time-domain approach. The model accounts for the dispersion of both gain and refractive index, nonlinear gain saturation from ultrafast...... processes, self-phase modulation, and spontaneous emission noise. Fluctuations of the mode-locked pulses are characterized from the fully distributed model using direct integration of noise-skirts in the phase-noise spectrum and the soliton perturbations introduced by Haus. We implement the model in order...

  6. Low-frequency fluctuation in multimode semiconductor laser subject to optical feedback

    Institute of Scientific and Technical Information of China (English)

    Xu Zhang; Huiying Ye; Zhaoxin Song

    2008-01-01

    Dynamics of a semiconductor laser subject to moderate optical feedback operating in the low-frequency fluctuation regime is numerically investigated.Multimode Lang-Kobayashi(LK)equations show that the low-frequency intensity dropout including the total intensity and sub-modes intensity is accompanied by sudden dropout simultaneously,which is in good agreement with experimental observation.The power fluctuation is quite annoying in practical applications,therefore it becomes important to study the mechanism of power fluctuation.It is also shown that many factors,such as spontaneous emission noise and feedback parameter,may influence power fluctuation larger than previously expected.

  7. Multi-user bidirectional communication using isochronal synchronisation of array of chaotic directly modulated semiconductor lasers

    International Nuclear Information System (INIS)

    Krishna, Bindu M.; John, Manu P.; Nandakumaran, V.M.

    2010-01-01

    Isochronal synchronisation between the elements of an array of three mutually coupled directly modulated semiconductor lasers is utilized for the purpose of simultaneous bidirectional secure communication. Chaotic synchronisation is achieved by adding the coupling signal to the self feedback signal provided to each element of the array. A symmetric coupling is effective in inducing synchronisation between the elements of the array. This coupling scheme provides a direct link between every pair of elements thus making the method suitable for simultaneous bidirectional communication between them. Both analog and digital messages are successfully encrypted and decrypted simultaneously by each element of the array.

  8. Pulsed laser deposition of II-VI and III-V semiconductor materials

    Energy Technology Data Exchange (ETDEWEB)

    Mele, A.; Di Palma, T.M.; Flamini, C.; Giardini Guidoni, A. [Rome, Univ. `La Sapienza` (Italy). Dep. di Chimica

    1998-12-01

    Pulsed laser irradiation of a solid target involves electronic excitation and heating, followed by expansion from the target of the elliptical gas cloud (plume) which can be eventually condensed on a suitable substrate. Pulsed laser ablation has been found to be a valuable technique to prepare II-VI and III-V thin films of semiconductor materials. Pulsed laser ablation deposition is discussed in the light of the results of an investigation on CdS, CdSe, CdTe and CdSe/CdTe multilayers and AIN, GaN and InN together with Al-Ga-In-N heterostructures. [Italiano] L`irradiazione di un target solido, mediante un fascio laser impulsato, genera una serie di processi che possono essere schematizzati come segue: riscaldamento ed eccitazione elettronica del target, da cui consegue l`espulsione di materiale sotto forma di una nube gassosa di forma ellissoidale (plume), che espande e puo` essere fatta depositare su un opportuno substrato. L`ablazione lasersi e` rivelata una tecnica valida per preparare film sottili di composti di elementi del II-VI e del III-V gruppo della tavola periodica. La deposizione via ablazione laser viene discussa alla luce dei risultati ottenuti nella preparazione di film di CdS, CdSe, CdTe e di film multistrato di CdSe/CdTe, di film di AIN, GaN, InN e di eterostrutture di Al-Ga-In-N.

  9. Frequency doubling of an InGaAs multiple quantum wells semiconductor disk laser

    Science.gov (United States)

    Lidan, Jiang; Renjiang, Zhu; Maohua, Jiang; Dingke, Zhang; Yuting, Cui; Peng, Zhang; Yanrong, Song

    2018-01-01

    We demonstrate a good beam quality 483 nm blue coherent radiation from a frequency doubled InGaAs multiple quantum wells semiconductor disk laser. The gain chip is consisted of 6 repeats of strain uncompensated InGaAs/GaAs quantum wells and 25 pairs of GaAs/AlAs distributed Bragg reflector. A 4 × 4 × 7 mm3 type I phase-matched BBO nonlinear crystal is used in a V-shaped laser cavity for the second harmonic generation, and 210 mW blue output power is obtained when the absorbed pump power is 3.5 W. The M2 factors of the laser beam in x and y directions are about 1.04 and 1.01, respectively. The output power of the blue laser is limited by the relatively small number of the multiple quantum wells, and higher power can be expected by increasing the number of the multiple quantum wells and improving the heat management of the laser.

  10. 1.9 W yellow, CW, high-brightness light from a high efficiency semiconductor laser-based system

    DEFF Research Database (Denmark)

    Hansen, Anders Kragh; Christensen, Mathias; Noordegraaf, Danny

    2017-01-01

    Semiconductor lasers are ideal sources for efficient electrical-to-optical power conversion and for many applications where their small size and potential for low cost are required to meet market demands. Yellow lasers find use in a variety of bio-related applications, such as photocoagulation......, imaging, flow cytometry, and cancer treatment. However, direct generation of yellow light from semiconductors with sufficient beam quality and power has so far eluded researchers. Meanwhile, tapered semiconductor lasers at near-infrared wavelengths have recently become able to provide neardiffraction...... power in just 60 seconds. An advantage of using a single pass configuration, rather than an external cavity configuration, is increased stability towards external perturbations. For example, stability to fluctuating case temperature over a 30 K temperature span has been demonstrated. The combination...

  11. Synchronization and bidirectional communication without delay line using strong mutually coupled semiconductor lasers

    Science.gov (United States)

    Li, Guang-Hui; Wang, An-Bang; Feng, Ye; Wang, Yang

    2010-07-01

    This paper numerically demonstrates synchronization and bidirectional communication without delay line by using two semiconductor lasers with strong mutual injection in a face-to-face configuration. These results show that both of the two lasers' outputs synchronize with their input chaotic carriers. In addition, simulations demonstrate that this kind of synchronization can be used to realize bidirectional communications without delay line. Further studies indicate that within a small deviation in message amplitudes of two sides (±6%), the message can be extracted with signal-noise-ratio more than 10 dB; and the signal-noise-ratio is extremely sensitive to the message rates mismatch of two sides, which may be used as a key of bidirectional communication.

  12. Synchronization and bidirectional communication without delay line using strong mutually coupled semiconductor lasers

    International Nuclear Information System (INIS)

    Guang-Hui, Li; An-Bang, Wang; Ye, Feng; Yang, Wang

    2010-01-01

    This paper numerically demonstrates synchronization and bidirectional communication without delay line by using two semiconductor lasers with strong mutual injection in a face-to-face configuration. These results show that both of the two lasers' outputs synchronize with their input chaotic carriers. In addition, simulations demonstrate that this kind of synchronization can be used to realize bidirectional communications without delay line. Further studies indicate that within a small deviation in message amplitudes of two sides (±6%), the message can be extracted with signal-noise-ratio more than 10 dB; and the signal-noise-ratio is extremely sensitive to the message rates mismatch of two sides, which may be used as a key of bidirectional communication. (general)

  13. Comparative study of the performance of semiconductor laser based coherent Doppler lidars

    DEFF Research Database (Denmark)

    Rodrigo, Peter John; Pedersen, Christian

    2012-01-01

    Coherent Doppler Lidars (CDLs), operating at an eye-safe 1.5-micron wavelength, have found promising applications in the optimization of wind-power production. To meet the wind-energy sector's impending demand for more cost-efficient industrial sensors, we have focused on the development of conti......Coherent Doppler Lidars (CDLs), operating at an eye-safe 1.5-micron wavelength, have found promising applications in the optimization of wind-power production. To meet the wind-energy sector's impending demand for more cost-efficient industrial sensors, we have focused on the development...... of continuous-wave CDL systems using compact, inexpensive semiconductor laser (SL) sources. In this work, we compare the performance of two candidate emitters for an allsemiconductor CDL system: (1) a monolithic master-oscillator-power-amplifier (MOPA) SL and (2) an external-cavity tapered diode laser (ECTDL)....

  14. Dual-comb spectroscopy of water vapor with a free-running semiconductor disk laser.

    Science.gov (United States)

    Link, S M; Maas, D J H C; Waldburger, D; Keller, U

    2017-06-16

    Dual-comb spectroscopy offers the potential for high accuracy combined with fast data acquisition. Applications are often limited, however, by the complexity of optical comb systems. Here we present dual-comb spectroscopy of water vapor using a substantially simplified single-laser system. Very good spectroscopy measurements with fast sampling rates are achieved with a free-running dual-comb mode-locked semiconductor disk laser. The absolute stability of the optical comb modes is characterized both for free-running operation and with simple microwave stabilization. This approach drastically reduces the complexity for dual-comb spectroscopy. Band-gap engineering to tune the center wavelength from the ultraviolet to the mid-infrared could optimize frequency combs for specific gas targets, further enabling dual-comb spectroscopy for a wider range of industrial applications. Copyright © 2017, American Association for the Advancement of Science.

  15. Selection of modes in transverse-mode waveguides for semiconductor lasers based on asymmetric heterostructures

    International Nuclear Information System (INIS)

    Slipchenko, S. O.; Bondarev, A. D.; Vinokurov, D. A.; Nikolaev, D. N.; Fetisova, N. V.; Sokolova, Z. N.; Pikhtin, N. A.; Tarasov, I. S.

    2009-01-01

    Asymmetric Al 0.3 Ga 0.7 As/GaAs/InGaAs heterostructures with a broadened waveguide produced by the method of MOCVD epitaxy are studied. It is established that the precision shift of the active region to one of the cladding layers ensures the generation of the chosen mode of high order in the transverse broadened waveguide. It is experimentally established that this shift brings about an increase in internal optical losses and a decrease in the internal quantum efficiency of stimulated emission. It is shown experimentally that the shift of the active region to the n-type cladding layer governs the sublinear form of the power-current characteristic for semiconductor lasers; in the case of a shift of the active region towards the p-type cladding layer, the laser diodes demonstrated a linear dependence of optical power on the pump current in the entire range of pump currents.

  16. Analytical model of ground-state lasing phenomenon in broadband semiconductor quantum dot lasers

    Science.gov (United States)

    Korenev, Vladimir V.; Savelyev, Artem V.; Zhukov, Alexey E.; Omelchenko, Alexander V.; Maximov, Mikhail V.

    2013-05-01

    We introduce an analytical approach to the description of broadband lasing spectra of semiconductor quantum dot lasers emitting via ground-state optical transitions of quantum dots. The explicit analytical expressions describing the shape and the width of lasing spectra as well as their temperature and injection current dependences are obtained in the case of low homogeneous broadening. It is shown that in this case these dependences are determined by only two dimensionless parameters, which are the dispersion of the distribution of QDs over the energy normalized to the temperature and loss-to-maximum gain ratio. The possibility of optimization of laser's active region size and structure by using the intentionally introduced disorder is also carefully considered.

  17. New semiconductor laser technology for gas sensing applications in the 1650nm range

    Science.gov (United States)

    Morrison, Gordon B.; Sherman, Jes; Estrella, Steven; Moreira, Renan L.; Leisher, Paul O.; Mashanovitch, Milan L.; Stephen, Mark; Numata, Kenji; Wu, Stewart; Riris, Haris

    2017-08-01

    Atmospheric methane (CH4) is the second most important anthropogenic greenhouse gas with approximately 25 times the radiative forcing of carbon dioxide (CO2) per molecule. CH4 also contributes to pollution in the lower atmosphere through chemical reactions leading to ozone production. Recent developments of LIDAR measurement technology for CH4 have been previously reported by Goddard Space Flight Center (GSFC). In this paper, we report on a novel, high-performance tunable semiconductor laser technology developed by Freedom Photonics for the 1650nm wavelength range operation, and for LIDAR detection of CH4. Devices described are monolithic, with simple control, and compatible with low-cost fabrication techniques. We present 3 different types of tunable lasers implemented for this application.

  18. Carrier-envelope offset frequency stabilization of an ultrafast semiconductor laser

    Science.gov (United States)

    Jornod, Nayara; Gürel, Kutan; Wittwer, Valentin J.; Brochard, Pierre; Hakobyan, Sargis; Schilt, Stéphane; Waldburger, Dominik; Keller, Ursula; Südmeyer, Thomas

    2018-02-01

    We present the self-referenced stabilization of the carrier-envelope offset (CEO) frequency of a semiconductor disk laser. The laser is a SESAM-modelocked VECSEL emitting at a wavelength of 1034 nm with a repetition frequency of 1.8 GHz. The 270-fs pulses are amplified to 3 W and compressed to 120 fs for the generation of a coherent octavespanning supercontinuum spectrum. A quasi-common-path f-to-2f interferometer enables the detection of the CEO beat with a signal-to-noise ratio of 30 dB sufficient for its frequency stabilization. The CEO frequency is phase-locked to an external reference with a feedback signal applied to the pump current.

  19. The unsaturated bistable stochastic resonance system.

    Science.gov (United States)

    Zhao, Wenli; Wang, Juan; Wang, Linze

    2013-09-01

    We investigated the characteristics of the output saturation of the classical continuous bistable system (saturation bistable system) and its impact on stochastic resonance (SR). We further proposed a piecewise bistable SR system (unsaturated bistable system) and developed the expression of signal-to-noise ratio (SNR) using the adiabatic approximation theory. Compared with the saturation bistable system, the SNR is significantly improved in our unsaturated bistable SR system. The numerical simulation showed that the unsaturated bistable system performed better in extracting weak signals from strong background noise than the saturation bistable system.

  20. Controlling bistability by linear augmentation

    International Nuclear Information System (INIS)

    Sharma, Pooja Rani; Shrimali, Manish Dev; Prasad, Awadhesh; Feudel, Ulrike

    2013-01-01

    In many bistable oscillating systems only one of the attractors is desired to possessing certain system performance. We present a method to drive a bistable system to a desired target attractor by annihilating the other one. This shift from bistability to monostability is achieved by augmentation of the nonlinear oscillator with a linear control system. For a proper choice of the control function one of the attractors disappears at a critical coupling strength in an control-induced boundary crisis. This transition from bistability to monostability is demonstrated with two paradigmatic examples, the autonomous Chua oscillator and a neuronal system with a periodic input signal.

  1. Bistable Mechanisms for Space Applications.

    Science.gov (United States)

    Zirbel, Shannon A; Tolman, Kyler A; Trease, Brian P; Howell, Larry L

    2016-01-01

    Compliant bistable mechanisms are monolithic devices with two stable equilibrium positions separated by an unstable equilibrium position. They show promise in space applications as nonexplosive release mechanisms in deployment systems, thereby eliminating friction and improving the reliability and precision of those mechanical devices. This paper presents both analytical and numerical models that are used to predict bistable behavior and can be used to create bistable mechanisms in materials not previously feasible for compliant mechanisms. Materials compatible with space applications are evaluated for use as bistable mechanisms and prototypes are fabricated in three different materials. Pin-puller and cutter release mechanisms are proposed as potential space applications.

  2. Bistable microelectromechanical actuator

    Science.gov (United States)

    Fleming, James G.

    1999-01-01

    A bistable microelectromechanical (MEM) actuator is formed on a substrate and includes a stressed membrane of generally rectangular shape that upon release assumes a curvilinear cross-sectional shape due to attachment at a midpoint to a resilient member and at opposing edges to a pair of elongate supports. The stressed membrane can be electrostatically switched between a pair of mechanical states having mirror-image symmetry, with the MEM actuator remaining in a quiescent state after a programming voltage is removed. The bistable MEM actuator according to various embodiments of the present invention can be used to form a nonvolatile memory element, an optical modulator (with a pair of mirrors supported above the membrane and moving in synchronism as the membrane is switched), a switchable mirror (with a single mirror supported above the membrane at the midpoint thereof) and a latching relay (with a pair of contacts that open and close as the membrane is switched). Arrays of bistable MEM actuators can be formed for applications including nonvolatile memories, optical displays and optical computing.

  3. Memory Effect on Adaptive Decision Making with a Chaotic Semiconductor Laser

    Directory of Open Access Journals (Sweden)

    Takatomo Mihana

    2018-01-01

    Full Text Available We investigate the effect of a memory parameter on the performance of adaptive decision making using a tug-of-war method with the chaotic oscillatory dynamics of a semiconductor laser. We experimentally generate chaotic temporal waveforms of the semiconductor laser with optical feedback and apply them for adaptive decision making in solving a multiarmed bandit problem that aims at maximizing the total reward from slot machines whose hit probabilities are dynamically switched. We examine the dependence of making correct decisions on different values of the memory parameter. The degree of adaptivity is found to be enhanced with a smaller memory parameter, whereas the degree of convergence to the correct decision is higher for a larger memory parameter. The relations among the adaptivity, environmental changes, and the difficulties of the problem are also discussed considering the requirement of past decisions. This examination of ultrafast adaptive decision making highlights the importance of memorizing past events and paves the way for future photonic intelligence.

  4. High temperature semiconductor diode laser pumps for high energy laser applications

    Science.gov (United States)

    Campbell, Jenna; Semenic, Tadej; Guinn, Keith; Leisher, Paul O.; Bhunia, Avijit; Mashanovitch, Milan; Renner, Daniel

    2018-02-01

    Existing thermal management technologies for diode laser pumps place a significant load on the size, weight and power consumption of High Power Solid State and Fiber Laser systems, thus making current laser systems very large, heavy, and inefficient in many important practical applications. To mitigate this thermal management burden, it is desirable for diode pumps to operate efficiently at high heat sink temperatures. In this work, we have developed a scalable cooling architecture, based on jet-impingement technology with industrial coolant, for efficient cooling of diode laser bars. We have demonstrated 60% electrical-to-optical efficiency from a 9xx nm two-bar laser stack operating with propylene-glycolwater coolant, at 50 °C coolant temperature. To our knowledge, this is the highest efficiency achieved from a diode stack using 50 °C industrial fluid coolant. The output power is greater than 100 W per bar. Stacks with additional laser bars are currently in development, as this cooler architecture is scalable to a 1 kW system. This work will enable compact and robust fiber-coupled diode pump modules for high energy laser applications.

  5. Photochemistry Aspects of the Laser Pyrolysis Addressing the Preparation of Oxide Semiconductor Photocatalysts

    Directory of Open Access Journals (Sweden)

    R. Alexandrescu

    2008-01-01

    Full Text Available The laser pyrolysis is a powerful and a versatile tool for the gas-phase synthesis of nanoparticles. In this paper, some fundamental and applicative characteristics of this technique are outlined and recent results obtained in the preparation of gamma iron oxide (γ-Fe2O3 and titania (TiO2 semiconductor nanostructures are illustrated. Nanosized iron oxide particles (4 to 9 nm diameter values have been directly synthesized by the laser-induced pyrolysis of a mixture containing iron pentacarbonyl/air (as oxidizer/ethylene (as sensitizer. Temperature-dependent Mossbauer spectroscopy shows that mainly maghemite is present in the sample obtained at higher laser power. The use of selected Fe2O3 samples for the preparation of water-dispersed magnetic nanofluids is also discussed. TiO2 nanoparticles comprising a mixture of anatase and rutile phases were synthesized via the laser pyrolysis of TiCl4- (vapors based gas-phase mixtures. High precursor concentration of the oxidizer was found to favor the prevalent anatase phase (about 90% in the titania nanopowders.

  6. Laser line scan underwater imaging by complementary metal-oxide-semiconductor camera

    Science.gov (United States)

    He, Zhiyi; Luo, Meixing; Song, Xiyu; Wang, Dundong; He, Ning

    2017-12-01

    This work employs the complementary metal-oxide-semiconductor (CMOS) camera to acquire images in a scanning manner for laser line scan (LLS) underwater imaging to alleviate backscatter impact of seawater. Two operating features of the CMOS camera, namely the region of interest (ROI) and rolling shutter, can be utilized to perform image scan without the difficulty of translating the receiver above the target as the traditional LLS imaging systems have. By the dynamically reconfigurable ROI of an industrial CMOS camera, we evenly divided the image into five subareas along the pixel rows and then scanned them by changing the ROI region automatically under the synchronous illumination by the fun beams of the lasers. Another scanning method was explored by the rolling shutter operation of the CMOS camera. The fun beam lasers were turned on/off to illuminate the narrow zones on the target in a good correspondence to the exposure lines during the rolling procedure of the camera's electronic shutter. The frame synchronization between the image scan and the laser beam sweep may be achieved by either the strobe lighting output pulse or the external triggering pulse of the industrial camera. Comparison between the scanning and nonscanning images shows that contrast of the underwater image can be improved by our LLS imaging techniques, with higher stability and feasibility than the mechanically controlled scanning method.

  7. Towards the generation of random bits at terahertz rates based on a chaotic semiconductor laser

    International Nuclear Information System (INIS)

    Kanter, Ido; Aviad, Yaara; Reidler, Igor; Cohen, Elad; Rosenbluh, Michael

    2010-01-01

    Random bit generators (RBGs) are important in many aspects of statistical physics and crucial in Monte-Carlo simulations, stochastic modeling and quantum cryptography. The quality of a RBG is measured by the unpredictability of the bit string it produces and the speed at which the truly random bits can be generated. Deterministic algorithms generate pseudo-random numbers at high data rates as they are only limited by electronic hardware speed, but their unpredictability is limited by the very nature of their deterministic origin. It is widely accepted that the core of any true RBG must be an intrinsically non-deterministic physical process, e.g. measuring thermal noise from a resistor. Owing to low signal levels, such systems are highly susceptible to bias, introduced by amplification, and to small nonrandom external perturbations resulting in a limited generation rate, typically less than 100M bit/s. We present a physical random bit generator, based on a chaotic semiconductor laser, having delayed optical feedback, which operates reliably at rates up to 300Gbit/s. The method uses a high derivative of the digitized chaotic laser intensity and generates the random sequence by retaining a number of the least significant bits of the high derivative value. The method is insensitive to laser operational parameters and eliminates the necessity for all external constraints such as incommensurate sampling rates and laser external cavity round trip time. The randomness of long bit strings is verified by standard statistical tests.

  8. Towards the generation of random bits at terahertz rates based on a chaotic semiconductor laser

    Science.gov (United States)

    Kanter, Ido; Aviad, Yaara; Reidler, Igor; Cohen, Elad; Rosenbluh, Michael

    2010-06-01

    Random bit generators (RBGs) are important in many aspects of statistical physics and crucial in Monte-Carlo simulations, stochastic modeling and quantum cryptography. The quality of a RBG is measured by the unpredictability of the bit string it produces and the speed at which the truly random bits can be generated. Deterministic algorithms generate pseudo-random numbers at high data rates as they are only limited by electronic hardware speed, but their unpredictability is limited by the very nature of their deterministic origin. It is widely accepted that the core of any true RBG must be an intrinsically non-deterministic physical process, e.g. measuring thermal noise from a resistor. Owing to low signal levels, such systems are highly susceptible to bias, introduced by amplification, and to small nonrandom external perturbations resulting in a limited generation rate, typically less than 100M bit/s. We present a physical random bit generator, based on a chaotic semiconductor laser, having delayed optical feedback, which operates reliably at rates up to 300Gbit/s. The method uses a high derivative of the digitized chaotic laser intensity and generates the random sequence by retaining a number of the least significant bits of the high derivative value. The method is insensitive to laser operational parameters and eliminates the necessity for all external constraints such as incommensurate sampling rates and laser external cavity round trip time. The randomness of long bit strings is verified by standard statistical tests.

  9. Quantifying the statistical complexity of low-frequency fluctuations in semiconductor lasers with optical feedback

    International Nuclear Information System (INIS)

    Tiana-Alsina, J.; Torrent, M. C.; Masoller, C.; Garcia-Ojalvo, J.; Rosso, O. A.

    2010-01-01

    Low-frequency fluctuations (LFFs) represent a dynamical instability that occurs in semiconductor lasers when they are operated near the lasing threshold and subject to moderate optical feedback. LFFs consist of sudden power dropouts followed by gradual, stepwise recoveries. We analyze experimental time series of intensity dropouts and quantify the complexity of the underlying dynamics employing two tools from information theory, namely, Shannon's entropy and the Martin, Plastino, and Rosso statistical complexity measure. These measures are computed using a method based on ordinal patterns, by which the relative length and ordering of consecutive interdropout intervals (i.e., the time intervals between consecutive intensity dropouts) are analyzed, disregarding the precise timing of the dropouts and the absolute durations of the interdropout intervals. We show that this methodology is suitable for quantifying subtle characteristics of the LFFs, and in particular the transition to fully developed chaos that takes place when the laser's pump current is increased. Our method shows that the statistical complexity of the laser does not increase continuously with the pump current, but levels off before reaching the coherence collapse regime. This behavior coincides with that of the first- and second-order correlations of the interdropout intervals, suggesting that these correlations, and not the chaotic behavior, are what determine the level of complexity of the laser's dynamics. These results hold for two different dynamical regimes, namely, sustained LFFs and coexistence between LFFs and steady-state emission.

  10. Band Gap Distortion in Semiconductors Strongly Driven by Intense Mid-Infrared Laser Fields

    Science.gov (United States)

    Kono, J.; Chin, A. H.

    2000-03-01

    Crystalline solids non-resonantly driven by intense time-periodic electric fields are predicted to exhibit unusual band-gap distortion.(e.g., Y. Yacoby, Phys. Rev. 169, 610 (1968); L.C.M. Miranda, Solid State Commun. 45, 783 (1983); J.Z. Kaminski, Acta Physica Polonica A 83, 495(1993).) Such non-perturbative effects have not been observed to date because of the unavoidable sample damage due to the very high intensity required using conventional lasers ( 1 eV photon energy). Here, we report the first clear evidence of laser-induced bandgap shrinkage in semiconductors under intense mid-infrared (MIR) laser fields. The use of long-wavelength light reduces the required intensity and prohibits strong interband absorption, thereby avoiding the damage problem. The significant sub-bandgap absorption persists only during the existence of the MIR laser pulse, indicating the virtual nature of the effect. We show that this particular example of non-perturbative behavior, known as the dynamical Franz-Keldysh effect, occurs when the effective ponderomotive potential energy is comparable to the photon energy of the applied field. This work was supported by ONR, NSF, JST and NEDO.

  11. Preparation of antimony sulfide semiconductor nanoparticles by pulsed laser ablation in liquid

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Ren-De, E-mail: son003@sekisui.com [Research & Development Institute, High Performance Plastics Company, Sekisui Chemical Co., Ltd. 2-1 Hyakuyama, Shimamoto-Cho, Mishima-Gun, Osaka, 618-0021 (Japan); Tsuji, Takeshi [Interdisciplinary Graduate School of Science and Engineering, Shimane University, 1060 Nishikawatsu-Cho, Matsue, 690-8504 (Japan)

    2015-09-01

    Highlights: • Pulsed laser ablation in liquid (LAL) was applied to prepare antimony sulfide nanoparticles (Sb{sub 2}S{sub 3} NPs). • Sb{sub 2}S{sub 3} NPs with a stoichiometric composition were successfully prepared by LAL in water without using any surfactants or capping agents. • Thus-prepared Sb{sub 2}S{sub 3} NPs showed low-temperature crystallization and melting at a temperature low as 200 °C. • The NPs-coated Sb{sub 2}S{sub 3} thin film showed comparable semiconductor properties (carrier mobility and carrier density) to the vacuum deposited one. • Byproducts such as CS{sub 2}, CH{sub 4} and CO were detected by GC-MS analysis when LAL was performed in organic solvent. • The LAL-induced decomposition mechanism of Sb{sub 2}S{sub 3} and organic solvents was discussed based on the GC-MS results. - Abstract: In this paper, we report on the synthesis of antimony sulfide (Sb{sub 2}S{sub 3}) semiconductor nanoparticles by pulsed laser ablation in liquid without using any surfactants or capping agents. Different results were obtained in water and organic solvents. In the case of water, Sb{sub 2}S{sub 3} nanoparticles with chemical compositions of stoichiometry were successfully prepared when laser irradiation was performed under the condition with the dissolved oxygen removed by argon gas bubbling. It was shown that thus-obtained Sb{sub 2}S{sub 3} nanoparticles exhibit features of not only low-temperature crystallization but also low-temperature melting at a temperature as low as 200 °C. Nanoparticle-coated Sb{sub 2}S{sub 3} thin films were found to show good visible light absorption and satisfying semiconductor properties (i.e., carrier mobility and density), which are essential for photovoltaic application. On the other hand, in the case of organic solvents (e.g., acetone, ethanol), such unexpected byproducts as CS{sub 2}, CO and CH{sub 4} were detected from the reaction system by GC-MS analysis, which suggests that both Sb{sub 2}S{sub 3} and organic

  12. Distributed processing in bistable perception

    NARCIS (Netherlands)

    Knapen, T.H.J.

    2007-01-01

    A very incisive way of studying visual awareness and the mechanisms that underlie it, it to use bistable perception. In bistable perception, an observer's perceptual state alternates between one interpretation and its mutually exclusive counterpart while the stimulus remains the same. This gives us

  13. Copper vapour laser with an efficient semiconductor pump generator having comparable pump pulse and output pulse durations

    Energy Technology Data Exchange (ETDEWEB)

    Yurkin, A A [P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2016-03-31

    We report the results of experimental studies of a copper vapour laser with a semiconductor pump generator capable of forming virtually optimal pump pulses with a current rise steepness of about 40 A ns{sup -1} in a KULON LT-1.5CU active element. To maintain the operating temperature of the active element's channel, an additional heating pulsed oscillator is used. High efficiency of the pump generator is demonstrated. (lasers)

  14. A full time-domain approach to spatio-temporal dynamics of semiconductor lasers. II. Spatio-temporal dynamics

    Science.gov (United States)

    Böhringer, Klaus; Hess, Ortwin

    The spatio-temporal dynamics of novel semiconductor lasers is discussed on the basis of a space- and momentum-dependent full time-domain approach. To this means the space-, time-, and momentum-dependent Full-Time Domain Maxwell Semiconductor Bloch equations, derived and discussed in our preceding paper I [K. Böhringer, O. Hess, A full time-domain approach to spatio-temporal dynamics of semiconductor lasers. I. Theoretical formulation], are solved by direct numerical integration. Focussing on the device physics of novel semiconductor lasers that profit, in particular, from recent advances in nanoscience and nanotechnology, we discuss the examples of photonic band edge surface emitting lasers (PBE-SEL) and semiconductor disc lasers (SDLs). It is demonstrated that photonic crystal effects can be obtained for finite crystal structures, and leading to a significant improvement in laser performance such as reduced lasing thresholds. In SDLs, a modern device concept designed to increase the power output of surface-emitters in combination with near-diffraction-limited beam quality, we explore the complex interplay between the intracavity optical fields and the quantum well gain material in SDL structures. Our simulations reveal the dynamical balance between carrier generation due to pumping into high energy states, momentum relaxation of carriers, and stimulated recombination from states near the band edge. Our full time-domain approach is shown to also be an excellent framework for the modelling of the interaction of high-intensity femtosecond and picosecond pulses with semiconductor nanostructures. It is demonstrated that group velocity dispersion, dynamical gain saturation and fast self-phase modulation (SPM) are the main causes for the induced changes and asymmetries in the amplified pulse shape and spectrum of an ultrashort high-intensity pulse. We attest that the time constants of the intraband scattering processes are critical to gain recovery. Moreover, we present

  15. Frequency-swept laser light source at 1050 nm with higher bandwidth due to multiple semiconductor optical amplifiers in series

    DEFF Research Database (Denmark)

    Marschall, Sebastian; Thrane, Lars; Andersen, Peter E.

    2009-01-01

    We report on the development of an all-fiber frequency-swept laser light source in the 1050 nm range based on semiconductor optical amplifiers (SOA) with improved bandwidth due to multiple gain media. It is demonstrated that even two SOAs with nearly equal gain spectra can improve the performance...

  16. Ultrafast dynamics of laser-pulse excited semiconductors: non-Markovian quantum kinetic equations with nonequilibrium correlations

    Directory of Open Access Journals (Sweden)

    V.V.Ignatyuk

    2004-01-01

    Full Text Available Non-Markovian kinetic equations in the second Born approximation are derived for a two-zone semiconductor excited by a short laser pulse. Both collision dynamics and running nonequilibrium correlations are taken into consideration. The energy balance and relaxation of the system to equilibrium are discussed. Results of numerical solution of the kinetic equations for carriers and phonons are presented.

  17. Degradation of Side-Mode Suppression Ratio in a DFB Laser Integrated With a Semiconductor Optical Amplifier

    DEFF Research Database (Denmark)

    Champagne, A.; Lestrade, Michel; Camel, Jérôme

    2004-01-01

    The degradation of the side-mode suppression ratio (SMSR) in a monolithically integrated distributed feedback laser and semiconductor optical amplifier (SOA) cavity is investigated. An expression is derived that gives the degradation of the SMSR in the case of a perfectly antireflection-coated SO...

  18. Pulsed laser deposition of semiconductor-ITO composite films on electric-field-applied substrates

    International Nuclear Information System (INIS)

    Narazaki, Aiko; Sato, Tadatake; Kawaguchi, Yoshizo; Niino, Hiroyuki; Yabe, Akira; Sasaki, Takeshi; Koshizaki, Naoto

    2002-01-01

    The DC electric-field effect on the crystallinity of II-VI semiconductor in composite systems has been investigated for CdS-ITO films fabricated via alternative pulsed laser deposition (PLD) of CdS and indium tin oxide (ITO) on electric-field-applied substrates. The alternative laser ablation was performed under irradiation of ArF excimer laser in mixture gas of helium and oxygen. The application of electric-field facilitated the preferential crystal-growth of CdS in nanometer scale at low pressure, whereas all the films grown without the field were amorphous. There is a large difference in the crystallization between the films grown on field-applied and heated substrates; the latter showed the crystal-growth with random orientations. This difference indicates that the existence of electric-field has an influence on the transformation from amorphous to crystalline phase of CdS. The driving force for the field-induced crystallization is also discussed in the light of the Joule heat

  19. Organic semiconductor rubrene thin films deposited by pulsed laser evaporation of solidified solutions

    Science.gov (United States)

    Majewska, N.; Gazda, M.; Jendrzejewski, R.; Majumdar, S.; Sawczak, M.; Śliwiński, G.

    2017-08-01

    Organic semiconductor rubrene (C42H28) belongs to most preferred spintronic materials because of the high charge carrier mobility up to 40 cm2(V·s)-1. However, the fabrication of a defect-free, polycrystalline rubrene for spintronic applications represents a difficult task. We report preparation and properties of rubrene thin films deposited by pulsed laser evaporation of solidified solutions. Samples of rubrene dissolved in aromatic solvents toluene, xylene, dichloromethane and 1,1-dichloroethane (0.23-1% wt) were cooled to temperatures in the range of 16.5-163 K and served as targets. The target ablation was provided by a pulsed 1064 nm or 266 nm laser. For films of thickness up to 100 nm deposited on Si, glass and ITO glass substrates, the Raman and AFM data show presence of the mixed crystalline and amorphous rubrene phases. Agglomerates of rubrene crystals are revealed by SEM observation too, and presence of oxide/peroxide (C42H28O2) in the films is concluded from matrix-assisted laser desorption/ionization time-of-flight spectroscopic analysis.

  20. Evolution of the Novalux extended cavity surface-emitting semiconductor laser (NECSEL)

    Science.gov (United States)

    McInerney, John G.

    2016-03-01

    Novalux Inc was an enterprise founded by Aram Mooradian in 1998 to commercialise a novel electrically pumped vertical extended cavity semiconductor laser platform, initially aiming to produce pump lasers for optical fiber telecommunication networks. Following successful major investment in 2000, the company developed a range of single- and multi-mode 980 nm pump lasers emitting from 100-500 mW with excellent beam quality and efficiency. This rapid development required solution of several significant problems in chip and external cavity design, substrate and DBR mirror optimization, thermal engineering and mode selection. Output coupling to single mode fiber was exceptional. Following the collapse of the long haul telecom market in late 2001, a major reorientation of effort was undertaken, initially to develop compact 60-100 mW hybrid monolithically integrated pumplets for metro/local amplified networks, then to frequency-doubled blue light emitters for biotech, reprographics and general scientific applications. During 2001-3 I worked at Novalux on a career break from University College Cork, first as R&D Director managing a small group tasked with producing new capabilities and product options based on the NECSEL platform, including high power, pulsed and frequency doubled versions, then in 2002 as Director of New Product Realization managing the full engineering team, leading the transition to frequency doubled products.

  1. Narrow-band modulation of semiconductor lasers at millimeter wave frequencies (7100 GHz) by mode locking

    International Nuclear Information System (INIS)

    Lau, K.Y.

    1990-01-01

    This paper reports on the possibility of mode locking a semiconductor laser at millimeter wave frequencies approaching and beyond 100 GHz which was investigated theoretically and experimentally. It is found that there are no fundamental theoretical limitations in mode locking at frequencies below 100 GHz. AT these high frequencies, only a few modes are locked and the output usually takes the form of a deep sinusoidal modulation which is synchronized in phase with the externally applied modulation at the intermodal heat frequency. This can be regarded for practical purposes as a highly efficient means of directly modulating an optical carrier over a narrow band at millimeter wave frequencies. Both active and passive mode locking are theoretically possible. Experimentally, predictions on active mode locking have been verified in prior publications up to 40 GHz. For passive mode locking, evidence consistent with passive mode locking was observed in an inhomogeneously pumped GaAIAs laser at a frequency of approximately 70 GHz. A large differential gain-absorption ratio such as that present in an inhomogeneously pumped single quantum well laser is necessary for pushing the passive mode-locking frequency beyond 100 GHz

  2. Continuously tunable solution-processed organic semiconductor DFB lasers pumped by laser diode

    DEFF Research Database (Denmark)

    Klinkhammer, Sönke; Liu, Xin; Huska, Klaus

    2012-01-01

    The fabrication and characterization of continuously tunable, solution-processed distributed feedback (DFB) lasers in the visible regime is reported. Continuous thin film thickness gradients were achieved by means of horizontal dipping of several conjugated polymer and blended small molecule solu...

  3. FY1995 ultra-high performance semiconductor lasers for advanced optical information network; 1995 nendo kodo hikari joho tsushinmo e muketa kyokugen seino handotai laser

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    The purpose of this research was to study and develop ultra-high performance semiconductor light source devices that should facilitate construction of advanced optical information networks. The semiconductor devices mentioned above are enhanced and integrated versions of distributed feedback (DFB) lasers based on 'gain coupling', which the group of the research coordinator has been investigating as a pioneer in the world. This research aimed at development of ultra-high performance semiconductor lasers that surpass the first generation conventional DFB lasers in any respect, by strengthening important device characteristics for system applications of the gain-coupled DFB lasers. The achievements of this research are listed below : 1. In-situ characterization of As-P exchange in MOVPE 2. Development of 1.55 {mu}m gain-coupled DFB lasers of absorptive grating type 3. Establishment of measurement technique for gain-coupling coefficients 4. Enlargement of small signal modulation response by the absorptive grating 5. Prediction of lower analog modulation distortion 6. Characterization of reflection-induced noise 7. Proposal and Demonstration of wavelength trimming 8. Proposal and Fabrication of GC DFB laser triode (NEDO)

  4. Chaos-based communications using semiconductor lasers subject to feedback from an integrated double cavity

    International Nuclear Information System (INIS)

    Tronciu, V Z; Mirasso, Claudio R; Colet, Pere

    2008-01-01

    We report the results of numerical investigations of the dynamical behaviour of an integrated device composed of a semiconductor laser and a double cavity that provides optical feedback. Due to the influence of the feedback, under the appropriate conditions, the system displays chaotic behaviour appropriate for chaos-based communications. The optimal conditions for chaos generation are identified. It is found that the double cavity feedback requires lower feedback strengths for developing high complexity chaos when compared with a single cavity. The synchronization of two unidirectional coupled (master-slave) systems and the influence of parameters mismatch on the synchronization quality are also studied. Finally, examples of message encoding and decoding are presented and discussed

  5. Switchable semiconductor optical fiber laser incorporating AWG and broadband FBG with high SMSR

    International Nuclear Information System (INIS)

    Ahmad, H; Zulkifli, M Z; Thambiratnam, K; Latiff, A A; Harun, S W

    2009-01-01

    In this paper we propose and demonstrate a switchable wavelength fiber laser (SWFL) using a semiconductor optical amplifier (SOA) together with an arrayed waveguide grating (AWG). The proposed SOA-based SWFL is capable of generating up to 14 lasing channels from 1530.1 nm to 1534.9 nm at a channel spacing of 0.8 nm (100 GHz) and a bandwidth of 11.8 and 10.2 nm respectively. The EDFA-based SWFL has a higher peak power at –5 dBm, while to SOA-based SWFL has a peak power of only –10 dBm. However, the SOA-based SWFL exhibits a much better SMSR of between 10 to 20 dB as compared to the SMSR of the EDFA-based SWFL due to the inhomogeneous broadening properties of the SOA

  6. ABC-model analysis of gain-switched pulse characteristics in low-dimensional semiconductor lasers

    Science.gov (United States)

    Bao, Xumin; Liu, Yuejun; Weng, Guoen; Hu, Xiaobo; Chen, Shaoqiang

    2018-01-01

    The gain-switching dynamics of low-dimensional semiconductor lasers is simulated numerically by using a two-dimensional rate-equation model. Use is also made of the ABC model, where the carrier recombination rate is described by a function of carrier densities including Shockley - Read - Hall (SRH) recombination coefficient A, spontaneous emission coefficient B and Auger recombination coefficient C. Effects of the ABC parameters on the ultrafast gain-switched pulse characteristics with high-density pulse excitation are analysed. It is found that while the parameter A has almost no obvious effects, the parameters B and C have distinctly different effects: B influences significantly the delay time of the gain-switched pulse, while C affects mainly the pulse intensity.

  7. Ultrasensitive detection of cell lysing in an microfabricated semiconductor laser cavity

    Energy Technology Data Exchange (ETDEWEB)

    Gourley, P.L.; French, T.; McDonald, A.E.; Shields, E.A. [Sandia National Labs., Albuquerque, NM (United States); Gourley, M.F. [Washington Hospital Center, Washington, DC (United States)

    1998-01-01

    In this paper the authors report investigations of semiconductor laser microcavities for use in detecting changes of human blood cells during lysing. By studying the spectra before and during mixing of blood fluids with de-ionized water, they are able to quantify the cell shape and concentration of hemoglobin in real time during the dynamical process of lysing. The authors find that the spectra can detect subtle changes that are orders of magnitude smaller than can be observed by standard optical microscopy. Such sensitivity in observing cell structural changes has implications for measuring cell fragility, monitoring apoptotic events in real time, development of photosensitizers for photodynamic therapy, and in-vitro cell micromanipulation techniques.

  8. Four distributed feedback laser array integrated with multimode-interference and semiconductor optical amplifier

    International Nuclear Information System (INIS)

    Ma Li; Zhu Hong-Liang; Liang Song; Zhao Ling-Juan; Chen Ming-Hua

    2013-01-01

    Monolithic integration of four 1.55-μm-range InGaAsP/InP distributed feedback (DFB) lasers using varied ridge width with a 4 × 1-multimode-interference (MMI) optical combiner and a semiconductor optical amplifier (SOA) is demonstrated. The average output power and the threshold current are 1.8 mW and 35 mA, respectively, when the injection current of the SOA is 100 mA, with a side mode suppression ratio (SMSR) exceeding 40 dB. The four channels have a 1-nm average channel spacing and can operate separately or simultaneously. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  9. Coherent Optical Generation of a 6 GHz Microwave Signal with Directly Phase Locked Semiconductor DFB Lasers

    DEFF Research Database (Denmark)

    Gliese, Ulrik Bo; Nielsen, Torben Nørskov; Bruun, Marlene

    1992-01-01

    Experimental results of a wideband heterodyne second order optical phase locked loop with 1.5 ¿m semiconductor lasers are presented. The loop has a bandwidth of 180 MHz, a gain of 181 dBHz and a propagation delay of only 400 ps. A beat signal of 8 MHz linewidth is phase locked to become a replica...... of a microwave reference source close to carrier with a noise level of ¿125 dBc/Hz. The total phase variance of the locked carrier is 0.04 rad2 and carriers can be generated in a continuous range from 3 to 18 GHz. The loop reliability is excellent with an average time to cycle slip of 1011 seconds...

  10. Optimization of Bistable Viscoelastic Systems

    DEFF Research Database (Denmark)

    Jensen, Kristian Ejlebjærg; Szabo, Peter; Okkels, Fridolin

    2014-01-01

    driving pressure corresponding to the point of bistability, such that the effect is enhanced. The point of bistability is, however, not explicitly contained in the solution, so we opt for a heuristic approach based on the dissipation ratio between the asymmetric and unstable symmetric flow solutions. We...... find a design that significantly reduces the driving pressure required for bistability, and furthermore is in agreement with the approach followed by experimental researchers. Furthermore, by comparing the two asymmetric solutions, we succesfully apply the same approach to a problem with two fluids...

  11. Optimisation of 1.3 μm strained-layer semiconductor lasers

    International Nuclear Information System (INIS)

    Pacey, C.

    1999-03-01

    The objectives of the research undertaken have been to investigate the properties of semiconductor lasers operating at around 1.3 μm. The aim of the investigation is to suggest modifications which give rise to improved operating characteristics especially in the high temperature (approaching 85 deg. C) range. The investigation can be divided into 2 sections: a theoretical approach and an experimental section. The theoretical study examined the performance of compressively strained InGaAsP/InP multiple quantum-well lasers emitting at 1.3 μm. in order to investigate the important factors and trends in the threshold current density and differential gain with strain, well width and well number. Structures with a fixed compressive strain of 1% but variable well width, and also with a fixed well width but variable strain from 0% to 1.4% have been considered. It has been found that there is little benefit to having compressive strains greater than 1%. For structures with a fixed 1% compressive strain and unstrained barriers, an optimum structure for lowest threshold current density and a high differential gain has been found to consist of six 35 A quantum-wells. In addition, compensated strain (CS) structures with compressive wells and tensile barriers have been examined. It is shown that the conduction band offset can be significantly increased and the valence band offset reduced in such structures, to give band-offset ratios comparable with aluminium based 1.3 μm devices. The gain calculations performed suggest that there is little degradation in the threshold carrier density or differential gain due to these alterations in the band offsets; and hence a better laser performance is expected due to a reduction in thermal leakage currents due to the improved electron confinement. The experimental study concentrates on looking at certain key design parameters to investigate their effect on the laser performance. These design parameters range from the number of quantum

  12. Rate equation analysis and non-Hermiticity in coupled semiconductor laser arrays

    Science.gov (United States)

    Gao, Zihe; Johnson, Matthew T.; Choquette, Kent D.

    2018-05-01

    Optically coupled semiconductor laser arrays are described by coupled rate equations. The coupled mode equations and carrier densities are included in the analysis, which inherently incorporate the carrier-induced nonlinearities including gain saturation and amplitude-phase coupling. We solve the steady-state coupled rate equations and consider the cavity frequency detuning and the individual laser pump rates as the experimentally controlled variables. We show that the carrier-induced nonlinearities play a critical role in the mode control, and we identify gain contrast induced by cavity frequency detuning as a unique mechanism for mode control. Photon-mediated energy transfer between cavities is also discussed. Parity-time symmetry and exceptional points in this system are studied. Unbroken parity-time symmetry can be achieved by judiciously combining cavity detuning and unequal pump rates, while broken symmetry lies on the boundary of the optical locking region. Exceptional points are identified at the intersection between broken symmetry and unbroken parity-time symmetry.

  13. Key Topics in Producing New Ultraviolet Led and Laser Devices Based on Transparent Semiconductor Zinc Oxide

    International Nuclear Information System (INIS)

    Tuezemen, S.

    2004-01-01

    Recently, it has been introduced that ZnO as II-VI semiconductor is promising various technological applications, especially for optoelectronic short wavelength light emitting devices due to its wide and direct band gap profile. The most important advantage of ZnO over the other currently used wide band gap semiconductors such as GaN is that its nearly 3 times higher exciton binding energy (60 meV), which permits efficient excitonic emission at room temperature and above. As-grown ZnO is normally n-type because of the Zn-rich defects such as zinc interstitials (Zn i ) oxygen vacancies (Vo), natively acting as shallow donors and main source of n-type conductivity in as-grown material. Therefore, making p-type ZnO has been more difficult due to unintentional compensation of possible acceptors by these residual donors. In order to develop electro luminescent and laser devices based on the ultraviolet (UV) exciton emission of ZnO, it will be important to fabricate good p-n junctions. Attempts to observe p-type conductivity in ours and our collaborators' laboratories in USA, either by co-doping with N or tuning O pressure have been first successful achievements, resulting in hole concentrations up to 10 1 9 cm - 3 in reactively sputtered thin layers of ZnO. Moreover, in order to produce ZnO based quantum well lasers similar to the previously introduced n-AlGaAs/GaAs/p-AlGaAs structures; we have attempted to grow Zn 1 -xSn x O thin films to enlarge the band gap energy. An increase up to 170 meV has been observed in Zn 1 -xSn x O thin films and this is enough barrier to be able to trap electron-hole pairs in quantum well structures. As a result, two important key issues; p-type conductivity and enhancement of the band gap energy in order to step forward towards the production of electro luminescent UV LEDs and quantum well lasers have been investigated and will be presented in this study

  14. A Miniature Coupled Bistable Vibration Energy Harvester

    International Nuclear Information System (INIS)

    Zhu, D; Arthur, D C; Beeby, S P

    2014-01-01

    This paper reports the design and test of a miniature coupled bistable vibration energy harvester. Operation of a bistable structure largely depends on vibration amplitude rather than frequency, which makes it very promising for wideband vibration energy harvesting applications. A coupled bistable structure consists of a pair of mobile magnets that create two potential wells and thus the bistable phenomenon. It requires lower excitation to trigger bistable operation compared to conventional bistable structures. Based on previous research, this work focused on miniaturisation of the coupled bistable structure for energy harvesting application. The proposed bistable energy harvester is a combination of a Duffing's nonlinear structure and a linear assisting resonator. Experimental results show that the output spectrum of the miniature coupled bistable vibration energy harvester was the superposition of several spectra. It had a higher maximum output power and a much greater bandwidth compared to simply the Duffing's structure without the assisting resonator

  15. Bistability of Cavity Magnon Polaritons

    Science.gov (United States)

    Wang, Yi-Pu; Zhang, Guo-Qiang; Zhang, Dengke; Li, Tie-Fu; Hu, C.-M.; You, J. Q.

    2018-01-01

    We report the first observation of the magnon-polariton bistability in a cavity magnonics system consisting of cavity photons strongly interacting with the magnons in a small yttrium iron garnet (YIG) sphere. The bistable behaviors emerged as sharp frequency switchings of the cavity magnon polaritons (CMPs) and related to the transition between states with large and small numbers of polaritons. In our experiment, we align, respectively, the [100] and [110] crystallographic axes of the YIG sphere parallel to the static magnetic field and find very different bistable behaviors (e.g., clockwise and counter-clockwise hysteresis loops) in these two cases. The experimental results are well fitted and explained as being due to the Kerr nonlinearity with either a positive or negative coefficient. Moreover, when the magnetic field is tuned away from the anticrossing point of CMPs, we observe simultaneous bistability of both magnons and cavity photons by applying a drive field on the lower branch.

  16. 1.9 W yellow, CW, high-brightness light from a high efficiency semiconductor laser-based system

    Science.gov (United States)

    Hansen, A. K.; Christensen, M.; Noordegraaf, D.; Heist, P.; Papastathopoulos, E.; Loyo-Maldonado, V.; Jensen, O. B.; Stock, M. L.; Skovgaard, P. M. W.

    2017-02-01

    Semiconductor lasers are ideal sources for efficient electrical-to-optical power conversion and for many applications where their small size and potential for low cost are required to meet market demands. Yellow lasers find use in a variety of bio-related applications, such as photocoagulation, imaging, flow cytometry, and cancer treatment. However, direct generation of yellow light from semiconductors with sufficient beam quality and power has so far eluded researchers. Meanwhile, tapered semiconductor lasers at near-infrared wavelengths have recently become able to provide neardiffraction- limited, single frequency operation with output powers up to 8 W near 1120 nm. We present a 1.9 W single frequency laser system at 562 nm, based on single pass cascaded frequency doubling of such a tapered laser diode. The laser diode is a monolithic device consisting of two sections: a ridge waveguide with a distributed Bragg reflector, and a tapered amplifier. Using single-pass cascaded frequency doubling in two periodically poled lithium niobate crystals, 1.93 W of diffraction-limited light at 562 nm is generated from 5.8 W continuous-wave infrared light. When turned on from cold, the laser system reaches full power in just 60 seconds. An advantage of using a single pass configuration, rather than an external cavity configuration, is increased stability towards external perturbations. For example, stability to fluctuating case temperature over a 30 K temperature span has been demonstrated. The combination of high stability, compactness and watt-level power range means this technology is of great interest for a wide range of biological and biomedical applications.

  17. Temporal nonlocality in bistable perception

    Science.gov (United States)

    Atmanspacher, Harald; Filk, Thomas

    2012-12-01

    A novel conceptual framework for theoretical psychology is presented and illustrated for the example of bistable perception. A basic formal feature of this framework is the non-commutativity of operations acting on mental states. A corresponding model for the bistable perception of ambiguous stimuli, the Necker-Zeno model, is sketched and some empirical evidence for it so far is described. It is discussed how a temporal nonlocality of mental states, predicted by the model, can be understood and tested.

  18. Stability of optically injected two-state quantum-dot lasers

    Energy Technology Data Exchange (ETDEWEB)

    Meinecke, Stefan; Lingnau, Benjamin; Roehm, Andre; Luedge, Kathy [Institut fuer Theoretische Physik, Technische Universitaet Berlin (Germany)

    2017-12-15

    Simultaneous two-state lasing is a unique property of semiconductor quantum-dot (QD) lasers. This not only changes steady-state characteristics of the laser device but also its dynamic response to perturbations. In this paper we investigate the dynamic stability of QD lasers in an external optical injection setup. Compared to conventional single-state laser devices, we find a strong suppression of dynamical instabilities in two-state lasers. Furthermore, depending on the frequency and intensity of the injected light, pronounced areas of bistability between both lasing frequencies appear, which can be employed for fast optical switching in all-optical photonic computing applications. These results emphasize the suitability of QD semiconductor lasers in future integrated optoelectronic systems where a high level of stability is required. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  19. Stability of optically injected two-state quantum-dot lasers

    International Nuclear Information System (INIS)

    Meinecke, Stefan; Lingnau, Benjamin; Roehm, Andre; Luedge, Kathy

    2017-01-01

    Simultaneous two-state lasing is a unique property of semiconductor quantum-dot (QD) lasers. This not only changes steady-state characteristics of the laser device but also its dynamic response to perturbations. In this paper we investigate the dynamic stability of QD lasers in an external optical injection setup. Compared to conventional single-state laser devices, we find a strong suppression of dynamical instabilities in two-state lasers. Furthermore, depending on the frequency and intensity of the injected light, pronounced areas of bistability between both lasing frequencies appear, which can be employed for fast optical switching in all-optical photonic computing applications. These results emphasize the suitability of QD semiconductor lasers in future integrated optoelectronic systems where a high level of stability is required. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Silicon photonics WDM transmitter with single section semiconductor mode-locked laser

    Science.gov (United States)

    Müller, Juliana; Hauck, Johannes; Shen, Bin; Romero-García, Sebastian; Islamova, Elmira; Azadeh, Saeed Sharif; Joshi, Siddharth; Chimot, Nicolas; Moscoso-Mártir, Alvaro; Merget, Florian; Lelarge, François; Witzens, Jeremy

    2015-04-01

    We demonstrate a wavelength domain-multiplexed (WDM) optical link relying on a single section semiconductor mode-locked laser (SS-MLL) with quantum dash (Q-Dash) gain material to generate 25 optical carriers spaced by 60.8 GHz, as well as silicon photonics (SiP) resonant ring modulators (RRMs) to modulate individual optical channels. The link requires optical reamplification provided by an erbium-doped fiber amplifier (EDFA) in the system experiments reported here. Open eye diagrams with signal quality factors (Q-factors) above 7 are measured with a commercial receiver (Rx). For higher compactness and cost effectiveness, reamplification of the modulated channels with a semiconductor optical amplifier (SOA) operated in the linear regime is highly desirable. System and device characterization indicate compatibility with the latter. While we expect channel counts to be primarily limited by the saturation output power level of the SOA, we estimate a single SOA to support more than eight channels. Prior to describing the system experiments, component design and detailed characterization results are reported including design and characterization of RRMs, ring-based resonant optical add-drop multiplexers (RR-OADMs) and thermal tuners, S-parameters resulting from the interoperation of RRMs and RR-OADMs, and characterization of Q-Dash SS-MLLs reamplified with a commercial SOA. Particular emphasis is placed on peaking effects in the transfer functions of RRMs and RR-OADMs resulting from transient effects in the optical domain, as well as on the characterization of SS-MLLs in regard to relative intensity noise (RIN), stability of the modes of operation, and excess noise after reamplification.

  1. Controlling the unstable emission of a semiconductor laser subject to conventional optical feedback with a filtered feedback branch.

    Science.gov (United States)

    Ermakov, I V; Tronciu, V Z; Colet, Pere; Mirasso, Claudio R

    2009-05-25

    We show the advantages of controlling the unstable dynamics of a semiconductor laser subject to conventional optical feedback by means of a second filtered feedback branch. We give an overview of the analytical solutions of the double cavity feedback and show numerically that the region of stabilization is much larger when using a second branch with filtered feedback than when using a conventional feedback one.

  2. Controlling the unstable emission of a semiconductor laser subject to conventional optical feedback with a filtered feedback branch

    OpenAIRE

    Ermakov, Ilya; Tronciu, Vasile; Colet, Pere; Mirasso, Claudio R.

    2009-01-01

    We show the advantages of controlling the unstable dynamics of a semiconductor laser subject to conventional optical feedback by means of a second filtered feedback branch. We give an overview of the analytical solutions of the double cavity feedback and show numerically that the region of stabilization is much larger when using a second branch with filtered feedback than when using a conventional feedback one.

  3. Field test of an all-semiconductor laser-based coherent continuous-wave Doppler lidar for wind energy applications

    DEFF Research Database (Denmark)

    Sjöholm, Mikael; Dellwik, Ebba; Hu, Qi

    -produced all-semiconductor laser. The instrument is a coherent continuous-wave lidar with two fixed-focus telescopes for launching laser beams in two different directions. The alternation between the telescopes is achieved by a novel switching technique without any moving parts. Here, we report results from...... signal strength from external atmospheric parameters such as relative humidity and concentrations of atmospheric particles is discussed. This novel lidar instrument design seems to offer a promising low-cost alternative for prevision remote sensing of wind turbine inflow....

  4. Simulation of the Optimized Structure of a Laterally Coupled Distributed Feedback (LC-DFB Semiconductor Laser Above Threshold

    Directory of Open Access Journals (Sweden)

    M. Seifouri

    2013-10-01

    Full Text Available In this paper, the laterally coupled distributed feedback semiconductor laser is studied. In the simulations performed, variations of structural parameters such as the grating amplitude a, the ridge width W, the thickness of the active region d, and other structural properties are considered. It is concluded that for certain values ​​of structural parameters, the laser maintains the highest output power, the lowest distortion Bragg frequency δL and the smallest changes in the wavelength λ. Above threshold, output power more than 40mW and SMSR values greater than 50 dB were achieved.

  5. High-Power Hybrid Mode-Locked External Cavity Semiconductor Laser Using Tapered Amplifier with Large Tunability

    Directory of Open Access Journals (Sweden)

    Andreas Schmitt-Sody

    2008-01-01

    Full Text Available We report on hybrid mode-locked laser operation of a tapered semiconductor amplifier in an external ring cavity, generating pulses as short as 0.5 ps at 88.1 MHz with an average power of 60 mW. The mode locking is achieved through a combination of a multiple quantum well saturable absorber (>10% modulation depth and an RF current modulation. This designed laser has 20 nm tuning bandwidth in continuous wave and 10 nm tuning bandwidth in mode locking around 786 nm center wavelength at constant temperature.

  6. Improvement in semiconductor laser printing using a sacrificial protecting layer for organic thin-film transistors fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Rapp, Ludovic, E-mail: rapp@lp3.univ-mrs.fr [Laboratoire LP3 (Lasers, Plasma et Procedes Photoniques) - UMR 6182 CNRS - Universite de la Mediterranee - Campus de Luminy C917, 13288 Marseille Cedex 09 (France); Cibert, Christophe [Laboratoire LP3 (Lasers, Plasma et Procedes Photoniques) - UMR 6182 CNRS - Universite de la Mediterranee - Campus de Luminy C917, 13288 Marseille Cedex 09 (France); Nenon, Sebastien [CINaM (Centre Interdisciplinaire de Nanoscience de Marseille) - UPR 3118 CNRS - Universite Aix Marseille, Case 913, Campus de Luminy, 13288 Marseille Cedex 09 (France); Alloncle, Anne Patricia [Laboratoire LP3 (Lasers, Plasma et Procedes Photoniques) - UMR 6182 CNRS - Universite de la Mediterranee - Campus de Luminy C917, 13288 Marseille Cedex 09 (France); Nagel, Matthias [Empa, Swiss Federal Laboratories for Materials Testing and Reasearch, Laboratory for Functional Polymers, Uberlandstrasse 129, 8600 Duebendorf (Switzerland); Lippert, Thomas [Paul Scherrer Institut, General Energy Research Department, 5232 Villigen PSI (Switzerland); Videlot-Ackermann, Christine; Fages, Frederic [CINaM (Centre Interdisciplinaire de Nanoscience de Marseille) - UPR 3118 CNRS - Universite Aix Marseille, Case 913, Campus de Luminy, 13288 Marseille Cedex 09 (France); Delaporte, Philippe [Laboratoire LP3 (Lasers, Plasma et Procedes Photoniques) - UMR 6182 CNRS - Universite de la Mediterranee - Campus de Luminy C917, 13288 Marseille Cedex 09 (France)

    2011-04-01

    Laser-induced forward transfer (LIFT) has been used to deposit pixels of an organic semiconductor, distyryl-quaterthiophenes (DS4T). The dynamics of the process have been investigated by shadowgraphic imaging for the nanosecond (ns) and picosecond (ps) regime on a time-scale from the laser iradiation to 1.5 {mu}s. The morphology of the deposit has been studied for different conditions. Intermediate sacrificial layer of gold or triazene polymer has been used to trap the incident radiation. Its role is to protect the layer to be transferred from direct irradiation and to provide a mechanical impulse strong enough to eject the material.

  7. Selective injection locking of a multi-mode semiconductor laser to a multi-frequency reference beam

    Science.gov (United States)

    Pramod, Mysore Srinivas; Yang, Tao; Pandey, Kanhaiya; Giudici, Massimo; Wilkowski, David

    2014-07-01

    Injection locking is a well known and commonly used method for coherent light amplification. Usually injection locking is obtained on a single-mode laser injected by a single-frequency seeding beam. In this work we show that selective injection locking of a single-frequency may also be achieved on a multi-mode semiconductor laser injected by a multi-frequency seeding beam, if the slave laser provides sufficient frequency filtering. This selective injection locking condition depends critically on the frequency detuning between the free-running slave emission frequency and each injected frequency component. Stable selective injection locking to a set of three seeding components separated by 1.2 GHz is obtained. This system provides an amplification up to 37 dB of each component. This result suggests that, using distinct slave lasers for each frequency line, a set of mutually coherent high-power radiation modes can be tuned in the GHz frequency domain.

  8. THE DETERMINATION OF A CRITICAL VALUE FOR DYNAMIC STABILITY OF SEMICONDUCTOR LASER DIODE WITH EXTERNAL OPTICAL FEEDBACK

    Directory of Open Access Journals (Sweden)

    Remzi YILDIRIM

    1998-01-01

    Full Text Available In this study, dynamic stability analysis of semiconductor laser diodes with external optical feedback has been realized. In the analysis the frequency response of the transfer function of laser diode H jw( , the transfer m function of laser diode with external optical feedback TF jw( , and optical feedback transfer function m K jw( obtained from small signal equations has been m accomplished using Nyquist stability analysis in complex domain. The effect of optical feedback on the stability of the system has been introduced and to bring the laser diode to stable condition the working critical boundary range of dampig frequency and reflection power constant (R has been determined. In the study the reflection power has been taken as ( .

  9. Piezo activated mode tracking system for widely tunable mode-hop-free external cavity mid-IR semiconductor lasers

    Science.gov (United States)

    Wysocki, Gerard (Inventor); Tittel, Frank K. (Inventor); Curl, Robert F. (Inventor)

    2010-01-01

    A widely tunable, mode-hop-free semiconductor laser operating in the mid-IR comprises a QCL laser chip having an effective QCL cavity length, a diffraction grating defining a grating angle and an external cavity length with respect to said chip, and means for controlling the QCL cavity length, the external cavity length, and the grating angle. The laser of claim 1 wherein said chip may be tuned over a range of frequencies even in the absence of an anti-reflective coating. The diffraction grating is controllably pivotable and translatable relative to said chip and the effective QCL cavity length can be adjusted by varying the injection current to the chip. The laser can be used for high resolution spectroscopic applications and multi species trace-gas detection. Mode-hopping is avoided by controlling the effective QCL cavity length, the external cavity length, and the grating angle so as to replicate a virtual pivot point.

  10. Rapid supersensitive laser-semiconductor monitoring system. Time period covered: Dec. 15, 1993 - Dec. 15, 1994

    International Nuclear Information System (INIS)

    Pugatch, V.M.

    2001-01-01

    The creation of the rapid and sensitive system for the determination of the Alpha-radioactivity in the Environmental samples has been determined as the main goal of the Research Contract No. 7200RO/RB. As a result of the first stage of the research accomplished in the year 1993, the prototype of the system based on the combination of the laser photoionization mass spectrometry and many-channel alpha-spectrometer has been built and tested. To improve the sensitivity it was proposed to add one more stage to the laser photoionization mass-spectrometer. To develop the high position sensitivity of the system it was proposed to include into the alpha-radiometer SI strip-detector with submicron position sensitivity. Hardware and software for the laser-semiconductor monitoring system of alpha-radionuclides in the environment have been further developed and tested in frames of the IAEA Research Contract No. 7200/R1/RB. Optimization of the sample evaporation with one more stage of photoionization has been successfully performed in the laser photoionization mass-spectrometer. The automatization of the measurement procedure is under way by means of the IBM PC-386 and specially designed electronic units. The evaluated sensitivity of the new set-up is in the range of 1.0 Bq/kg. A bulk measurement of the alpha-radioactivity concentration in soil samples from the Chernobyl region (100 km) have been performed by means of thick samples method and built under this contract alpha-radiometer with large area SI semiconductor detectors. The lowest detectable level was in the range 100 Bq/kg without any radiochemical separation. Comparison with the data obtained for the same probes by means of the thin sample (with radiochemical separation) has shown higher Pu-concentration values obtained by means of the thick samples. For the first time the Sl-strip-detector with 128 channels has been applied for the alpha-radiometry purposes. Different read-out electronics (including the most

  11. Perceptual incongruence influences bistability and cortical activation

    NARCIS (Netherlands)

    Brouwer, G.J.; Tong, F.; Hagoort, P.; van Ee, R.

    2009-01-01

    We employed a parametric psychophysical design in combination with functional imaging to examine the influence of metric changes in perceptual incongruence on perceptual alternation rates and cortical responses. Subjects viewed a bistable stimulus defined by incongruent depth cues; bistability

  12. GABA shapes the dynamics of bistable perception

    NARCIS (Netherlands)

    van Loon, A.M.; Knapen, T.; Scholte, H.S.; St. John-Saaltink, E.; Donner, T.H.; Lamme, V.A.F.

    2013-01-01

    Sometimes, perception fluctuates spontaneously between two distinct interpretations of a constant sensory input. These bistable perceptual phenomena provide a unique window into the neural mechanisms that create the contents of conscious perception. Models of bistable perception posit that mutual

  13. Semiconductor Nanomaterials-Based Fluorescence Spectroscopic and Matrix-Assisted Laser Desorption/Ionization (MALDI Mass Spectrometric Approaches to Proteome Analysis

    Directory of Open Access Journals (Sweden)

    Suresh Kumar Kailasa

    2013-12-01

    Full Text Available Semiconductor quantum dots (QDs or nanoparticles (NPs exhibit very unusual physico-chemcial and optical properties. This review article introduces the applications of semiconductor nanomaterials (NMs in fluorescence spectroscopy and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS for biomolecule analysis. Due to their unique physico-chemical and optical properties, semiconductors NMs have created many new platforms for investigating biomolecular structures and information in modern biology. These semiconductor NMs served as effective fluorescent probes for sensing proteins and cells and acted as affinity or concentrating probes for enriching peptides, proteins and bacteria proteins prior to MALDI-MS analysis.

  14. Network connectivity enhancement by exploiting all optical multicast in semiconductor ring laser

    Science.gov (United States)

    Siraj, M.; Memon, M. I.; Shoaib, M.; Alshebeili, S.

    2015-03-01

    The use of smart phone and tablet applications will provide the troops for executing, controlling and analyzing sophisticated operations with the commanders providing crucial documents directly to troops wherever and whenever needed. Wireless mesh networks (WMNs) is a cutting edge networking technology which is capable of supporting Joint Tactical radio System (JTRS).WMNs are capable of providing the much needed bandwidth for applications like hand held radios and communication for airborne and ground vehicles. Routing management tasks can be efficiently handled through WMNs through a central command control center. As the spectrum space is congested, cognitive radios are a much welcome technology that will provide much needed bandwidth. They can self-configure themselves, can adapt themselves to the user requirement, provide dynamic spectrum access for minimizing interference and also deliver optimal power output. Sometimes in the indoor environment, there are poor signal issues and reduced coverage. In this paper, a solution utilizing (CR WMNs) over optical network is presented by creating nanocells (PCs) inside the indoor environment. The phenomenon of four-wave mixing (FWM) is exploited to generate all-optical multicast using semiconductor ring laser (SRL). As a result same signal is transmitted at different wavelengths. Every PC is assigned a unique wavelength. By using CR technology in conjunction with PC will not only solve network coverage issue but will provide a good bandwidth to the secondary users.

  15. Electrical addressing and temporal tweezing of localized pulses in passively mode-locked semiconductor lasers

    Science.gov (United States)

    Javaloyes, J.; Camelin, P.; Marconi, M.; Giudici, M.

    2017-08-01

    This work presents an overview of a combined experimental and theoretical analysis on the manipulation of temporal localized structures (LSs) found in passively Vertical-Cavity Surface-Emitting Lasers coupled to resonant saturable absorber mirrors. We show that the pumping current is a convenient parameter for manipulating the temporal Localized Structures, also called localized pulses. While short electrical pulses can be used for writing and erasing individual LSs, we demonstrate that a current modulation introduces a temporally evolving parameter landscape allowing to control the position and the dynamics of LSs. We show that the localized pulses drifting speed in this landscape depends almost exclusively on the local parameter value instead of depending on the landscape gradient, as shown in quasi-instantaneous media. This experimental observation is theoretically explained by the causal response time of the semiconductor carriers that occurs on an finite timescale and breaks the parity invariance along the cavity, thus leading to a new paradigm for temporal tweezing of localized pulses. Different modulation waveforms are applied for describing exhaustively this paradigm. Starting from a generic model of passive mode-locking based upon delay differential equations, we deduce the effective equations of motion for these LSs in a time-dependent current landscape.

  16. Tunable and broadband microwave frequency combs based on a semiconductor laser with incoherent optical feedback

    International Nuclear Information System (INIS)

    Zhao Mao-Rong; Wu Zheng-Mao; Deng Tao; Zhou Zhen-Li; Xia Guang-Qiong

    2015-01-01

    Based on a semiconductor laser (SL) with incoherent optical feedback, a novel all-optical scheme for generating tunable and broadband microwave frequency combs (MFCs) is proposed and investigated numerically. The results show that, under suitable operation parameters, the SL with incoherent optical feedback can be driven to operate at a regular pulsing state, and the generated MFCs have bandwidths broader than 40 GHz within a 10 dB amplitude variation. For a fixed bias current, the line spacing (or repetition frequency) of the MFCs can be easily tuned by varying the feedback delay time and the feedback strength, and the tuning range of the line spacing increases with the increase in the bias current. The linewidth of the MFCs is sensitive to the variation of the feedback delay time and the feedback strength, and a linewidth of tens of KHz can be achieved through finely adjusting the feedback delay time and the feedback strength. In addition, mappings of amplitude variation, repetition frequency, and linewidth of MFCs in the parameter space of the feedback delay time and the feedback strength are presented. (paper)

  17. Dynamics of temporally localized states in passively mode-locked semiconductor lasers

    Science.gov (United States)

    Schelte, C.; Javaloyes, J.; Gurevich, S. V.

    2018-05-01

    We study the emergence and the stability of temporally localized structures in the output of a semiconductor laser passively mode locked by a saturable absorber in the long-cavity regime. For large yet realistic values of the linewidth enhancement factor, we disclose the existence of secondary dynamical instabilities where the pulses develop regular and subsequent irregular temporal oscillations. By a detailed bifurcation analysis we show that additional solution branches that consist of multipulse (molecules) solutions exist. We demonstrate that the various solution curves for the single and multipeak pulses can splice and intersect each other via transcritical bifurcations, leading to a complex web of solutions. Our analysis is based on a generic model of mode locking that consists of a time-delayed dynamical system, but also on a much more numerically efficient, yet approximate, partial differential equation. We compare the results of the bifurcation analysis of both models in order to assess up to which point the two approaches are equivalent. We conclude our analysis by the study of the influence of group velocity dispersion, which is only possible in the framework of the partial differential equation model, and we show that it may have a profound impact on the dynamics of the localized states.

  18. Discretely tunable micromachined injection-locked lasers

    International Nuclear Information System (INIS)

    Cai, H; Yu, M B; Lo, G Q; Kwong, D L; Zhang, X M; Liu, A Q; Liu, B

    2010-01-01

    This paper reports a micromachined injection-locked laser (ILL) to provide tunable discrete wavelengths. It utilizes a non-continuously tunable laser as the master to lock a Fabry–Pérot semiconductor laser chip. Both lasers are integrated into a deep-etched silicon chip with dimensions of 3 mm × 3 mm × 0.8 mm. Based on the experimental results, significant improvements in the optical power and spectral purity have been achieved in the fully locked state, and optical hysteresis and bistability have also been observed in response to the changes of the output wavelength and optical power of the master laser. As a whole system, the micromachined ILL is able to provide single mode, discrete wavelength tuning, high power and direct modulation with small size and single-chip solution, making it promising for advanced optical communications such as wavelength division multiplexing optical access networks.

  19. Wafer-scale laser pantography: Fabrication of n-metal-oxide-semiconductor transistors and small-scale integrated circuits by direct-write laser-induced pyrolytic reactions

    International Nuclear Information System (INIS)

    McWilliams, B.M.; Herman, I.P.; Mitlitsky, F.; Hyde, R.A.; Wood, L.L.

    1983-01-01

    A complete set of processes sufficient for manufacture of n-metal-oxide-semiconductor (n-MOS) transistors by a laser-induced direct-write process has been demonstrated separately, and integrated to yield functional transistors. Gates and interconnects were fabricated of various combinations of n-doped and intrinsic polysilicon, tungsten, and tungsten silicide compounds. Both 0.1-μm and 1-μm-thick gate oxides were micromachined with and without etchant gas, and the exposed p-Si [100] substrate was cleaned and, at times, etched. Diffusion regions were doped by laser-induced pyrolytic decomposition of phosphine followed by laser annealing. Along with the successful manufacture of working n-MOS transistors and a set of elementary digital logic gates, this letter reports the successful use of several laser-induced surface reactions that have not been reported previously

  20. Optical bistability without the rotating wave approximation

    Energy Technology Data Exchange (ETDEWEB)

    Sharaby, Yasser A., E-mail: Yasser_Sharaby@hotmail.co [Physics Department, Faculty of Applied Sciences, Suez Canal University, Suez (Egypt); Joshi, Amitabh, E-mail: ajoshi@eiu.ed [Department of Physics, Eastern Illinois University, Charleston, IL 61920 (United States); Hassan, Shoukry S., E-mail: Shoukryhassan@hotmail.co [Mathematics Department, College of Science, University of Bahrain, P.O. Box 32038 (Bahrain)

    2010-04-26

    Optical bistability for two-level atomic system in a ring cavity is investigated outside the rotating wave approximation (RWA) using non-autonomous Maxwell-Bloch equations with Fourier decomposition up to first harmonic. The first harmonic output field component exhibits reversed or closed loop bistability simultaneously with the usual (anti-clockwise) bistability in the fundamental field component.

  1. Optical bistability without the rotating wave approximation

    International Nuclear Information System (INIS)

    Sharaby, Yasser A.; Joshi, Amitabh; Hassan, Shoukry S.

    2010-01-01

    Optical bistability for two-level atomic system in a ring cavity is investigated outside the rotating wave approximation (RWA) using non-autonomous Maxwell-Bloch equations with Fourier decomposition up to first harmonic. The first harmonic output field component exhibits reversed or closed loop bistability simultaneously with the usual (anti-clockwise) bistability in the fundamental field component.

  2. Development and characterization of a semi-conductor laser sensor for real time measurement and identification of atmospheric pollutants

    International Nuclear Information System (INIS)

    Boulos, F.; Zaatar, Y.; Atanas, J.P.; Bechara, J.

    2004-01-01

    Full text.Tunable diode laser absorption spectroscopy (TDLAS) in the near infrared (NIR) using semiconductor lasers of compounds between elements of group III (Ga, Al and In) and group V (P, As and Sb) is being increasingly used in various environmental and industrial process control applications. This technique exploits the unique properties of these laser materials i.e., high coherence, high monochromaticity, low divergence and high brightness to permit rapid sensitive detection with high selectivity and spectral resolution. A computer-interfaced near infrared semiconductor laser sensor has been developed in our laboratory for spectroscopic applications in air pollution monitoring. The sensor can be operated in two configurations: open path free beam coupled to a multiple pass White cell and fiber optic guided beam coupled to an evanescent wave sensor. This paper will present an overview of the system's modulation, sensing and data acquisition methods and some recent measurement results, together with a description of ongoing research and development for the improvement of the system's performance and sensitivity

  3. Dynamic optical bistability in resonantly enhanced Raman generation

    International Nuclear Information System (INIS)

    Novikova, I.; Phillips, D.F.; Zibrov, A.S.; Andre, A.; Walsworth, R.L.

    2004-01-01

    We report observations of novel dynamic behavior in resonantly enhanced stimulated Raman scattering in Rb vapor. In particular, we demonstrate a dynamic hysteresis of the Raman scattered optical field in response to changes of the drive laser field intensity and/or frequency. This effect may be described as a dynamic form of optical bistability resulting from the formation and decay of atomic coherence. We have applied this phenomenon to the realization of an all-optical switch

  4. Bistable microvalve and microcatheter system

    Science.gov (United States)

    Seward, Kirk Patrick

    2003-05-20

    A bistable microvalve of shape memory material is operatively connected to a microcatheter. The bistable microvalve includes a tip that can be closed off until it is in the desired position. Once it is in position it can opened and closed. The system uses heat and pressure to open and close the microvalve. The shape memory material will change stiffness and shape when heated above a transition temperature. The shape memory material is adapted to move from a first shape to a second shape, either open or closed, where it can perform a desired function.

  5. Laser-based irradiation apparatus and method to measure the functional dose-rate response of semiconductor devices

    Science.gov (United States)

    Horn, Kevin M [Albuquerque, NM

    2008-05-20

    A broad-beam laser irradiation apparatus can measure the parametric or functional response of a semiconductor device to exposure to dose-rate equivalent infrared laser light. Comparisons of dose-rate response from before, during, and after accelerated aging of a device, or from periodic sampling of devices from fielded operational systems can determine if aging has affected the device's overall functionality. The dependence of these changes on equivalent dose-rate pulse intensity and/or duration can be measured with the apparatus. The synchronized introduction of external electrical transients into the device under test can be used to simulate the electrical effects of the surrounding circuitry's response to a radiation exposure while exposing the device to dose-rate equivalent infrared laser light.

  6. Optical dynamics in low-dimensional semiconductor heterostructures. Quantum dots and quantum cascade lasers

    Energy Technology Data Exchange (ETDEWEB)

    Weber, Carsten

    2008-07-01

    This work is focused on the optical dynamics of mesoscopic semiconductor heterostructures, using as prototypes zero-dimensional quantum dots and quantum cascade lasers which consist of quasitwo- dimensional quantum wells. Within a density matrix theory, a microscopic many-particle theory is applied to study scattering effects in these structures: the coupling to external as well as local fields, electron-phonon coupling, coupling to impurities, and Coulomb coupling. For both systems, the investigated effects are compared to experimentally observed results obtained during the past years. In quantum dots, the three-dimensional spatial confinement leads to the necessity to consider a quantum kinetic description of the dynamics, resulting in non-Markovian electron-phonon effects. This can be seen in the spectral phonon sidebands due to interaction with acoustic phonons as well as a damping of nonlinear Rabi oscillations which shows a nonmonotonous intensity and pulse duration dependence. An analysis of the inclusion of the self-interaction of the quantum dot shows that no dynamical local field terms appear for the simple two-level model. Considering local fields which have their origin in many quantum dots, consequences for a two-level quantum dot such as a zero-phonon line broadening and an increasing signal in photon echo experiments are found. For the use of quantum dots in an optical spin control scheme, it is found that the dephasing due to the electron-phonon interaction can be dominant in certain regimes. Furthermore, soliton and breather solutions are studied analytically in nonlinear quantum dot ensembles. Generalizing to quasi-two-dimensional structures, the intersubband dynamics of quantum cascade laser structures is investigated. A dynamical theory is considered in which the temporal evolution of the subband populations and the current density as well as the influence of scattering effects is studied. In the nonlinear regime, the scattering dependence and

  7. Molecular beam epitaxy growth and characterization of two-six materials for visible semiconductor lasers

    Science.gov (United States)

    Zeng, Linfei

    This thesis proposes the molecular beam epitaxy (MBE) growth and characterization of a new Znsb{x}Cdsb{y}Mgsb{(1-x-y)}Se based semiconductor materials system on InP substrates for visible light emitting diodes (LED) and lasers. The growth conditions for lattice-matched Znsb{x}Cdsb{y}Mgsb{(1-x-y)}Se layers with the desired bandgap have been established and optimized. A chemical etching technique to measure the defect density of Znsb{x}Cdsb{y}Mgsb{(1-x-y)}Se materials has been established. The accuracy of this method for revealing stacking faults and dislocations was verified by plan-view TEM. Using the techniques such as III-V buffer layer, Zn-irradiation, low-temperature growth, ZnCdSe interfacial layer and growth interruption to improve the quality of the interface of III-V and II-VI, the material quality of Znsb{x}Cdsb{y}Mgsb{(1-x-y)}Se has been improved dramatically. Defect density has been reduced from 10sp{10}\\ cmsp{-2} to {˜}5×10sp4\\ cmsp{-2}. The properties of this material system such as the quality and strain state in the epilayer, the dependence of bandgap on temperature, and the band offset have been studied by using double crystal x-ray diffraction, photoluminescence and capacitance voltage measurements. The ZnCdSe/ZnCdMgSe based quantum well (QW) structures have been grown and studied. Optically pumped lasing with emission range from red to blue has been obtained from ZnCdSe/ZnCdMgSe based separate-confinement single QW laser structures. The results demonstrate the potential for these materials as integrated full color display devices. Preliminary studies of the degradation behavior of ZnCdSe/ZnCdMgSe QW were performed. No dark line defects (DLDs) were observed during the degradation. A very strong room temperature differential negative resistance behavior was observed from Al/Znsb{0.61}Cdsb{0.39}Se/nsp+-InP devices, which is useful in millimeter-wave applications. We also found that these devices can be set to either in highly conductive or

  8. Applications of confocal laser scanning microscopy in research into organic semiconductor thin films

    DEFF Research Database (Denmark)

    Schiek, Manuela; Balzer, Frank

    2014-01-01

    At the center of opto-electronic devices are thin layers of organic semiconductors, which need to be sandwiched between planar electrodes. With the growing demand for opto-electronic devices now and in the future, new electrode materials are needed to meet the requirements of organic semiconductors...

  9. Bistable Helmholtz solitons in cubic-quintic materials

    International Nuclear Information System (INIS)

    Christian, J. M.; McDonald, G. S.; Chamorro-Posada, P.

    2007-01-01

    We propose a nonlinear Helmholtz equation for modeling the evolution of broad optical beams in media with a cubic-quintic intensity-dependent refractive index. This type of nonlinearity is appropriate for some semiconductor materials, glasses, and polymers. Exact analytical soliton solutions are presented that describe self-trapped nonparaxial beams propagating at any angle with respect to the reference direction. These spatially symmetric solutions are, to the best of our knowledge, the first bistable Helmholtz solitons to be derived. Accompanying conservation laws (both integral and particular forms) are also reported. Numerical simulations investigate the stability of the solitons, which appear to be remarkably robust against perturbations

  10. Flexible Bistable Cholesteric Reflective Displays

    Science.gov (United States)

    Yang, Deng-Ke

    2006-03-01

    Cholesteric liquid crystals (ChLCs) exhibit two stable states at zero field condition-the reflecting planar state and the nonreflecting focal conic state. ChLCs are an excellent candidate for inexpensive and rugged electronic books and papers. This paper will review the display cell structure,materials and drive schemes for flexible bistable cholesteric (Ch) reflective displays.

  11. Bi-stable optical actuator

    Science.gov (United States)

    Holdener, Fred R.; Boyd, Robert D.

    2000-01-01

    The present invention is a bi-stable optical actuator device that is depowered in both stable positions. A bearing is used to transfer motion and smoothly transition from one state to another. The optical actuator device may be maintained in a stable position either by gravity or a restraining device.

  12. Multistate intermittency on the route to chaos of a semiconductor laser subjected to optical feedback from a long external cavity.

    Science.gov (United States)

    Choi, Daeyoung; Wishon, Michael J; Chang, C Y; Citrin, D S; Locquet, A

    2018-01-01

    We observe experimentally two regimes of intermittency on the route to chaos of a semiconductor laser subjected to optical feedback from a long external cavity as the feedback level is increased. The first regime encountered corresponds to multistate intermittency involving two or three states composed of several combinations of periodic, quasiperiodic, and subharmonic dynamics. The second regime is observed for larger feedback levels and involves intermittency between period-doubled and chaotic regimes. This latter type of intermittency displays statistical properties similar to those of on-off intermittency.

  13. Multichannel, time-resolved picosecond laser ultrasound imaging and spectroscopy with custom complementary metal-oxide-semiconductor detector

    International Nuclear Information System (INIS)

    Smith, Richard J.; Light, Roger A.; Johnston, Nicholas S.; Pitter, Mark C.; Somekh, Mike G.; Sharples, Steve D.

    2010-01-01

    This paper presents a multichannel, time-resolved picosecond laser ultrasound system that uses a custom complementary metal-oxide-semiconductor linear array detector. This novel sensor allows parallel phase-sensitive detection of very low contrast modulated signals with performance in each channel comparable to that of a discrete photodiode and a lock-in amplifier. Application of the instrument is demonstrated by parallelizing spatial measurements to produce two-dimensional thickness maps on a layered sample, and spectroscopic parallelization is demonstrated by presenting the measured Brillouin oscillations from a gallium arsenide wafer. This paper demonstrates the significant advantages of our approach to pump probe systems, especially picosecond ultrasonics.

  14. Multichannel, time-resolved picosecond laser ultrasound imaging and spectroscopy with custom complementary metal-oxide-semiconductor detector

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Richard J.; Light, Roger A.; Johnston, Nicholas S.; Pitter, Mark C.; Somekh, Mike G. [Institute of Biophysics, Imaging and Optical Science, University of Nottingham, Nottinghamshire NG7 2RD (United Kingdom); Sharples, Steve D. [Applied Optics Group, Electrical Systems and Optics Research Division, University of Nottingham, Nottinghamshire NG7 2RD (United Kingdom)

    2010-02-15

    This paper presents a multichannel, time-resolved picosecond laser ultrasound system that uses a custom complementary metal-oxide-semiconductor linear array detector. This novel sensor allows parallel phase-sensitive detection of very low contrast modulated signals with performance in each channel comparable to that of a discrete photodiode and a lock-in amplifier. Application of the instrument is demonstrated by parallelizing spatial measurements to produce two-dimensional thickness maps on a layered sample, and spectroscopic parallelization is demonstrated by presenting the measured Brillouin oscillations from a gallium arsenide wafer. This paper demonstrates the significant advantages of our approach to pump probe systems, especially picosecond ultrasonics.

  15. The dynamics of the laser-induced metal-semiconductor phase transition of samarium sulfide (SmS)

    International Nuclear Information System (INIS)

    Kaempfer, Tino

    2009-01-01

    The present thesis is dedicated to the experimental study of the metal-semiconductor phase transition of samarium sulfide (SmS): Temperature- and time-resolved experiments on the characterization of the phase transition of mixed-valence SmS samples (M-SmS) are presented. The measurement of the dynamics of the laser-induced phase transition pursues via time-resolved ultrashort-time microscopy and by X-ray diffraction with sub-picosecond time resolution. The electronic and structural processes, which follow an excitation of M-SmS with infrared femtosecond laser pulses, are physically interpreted on the base of the results obtained in this thesis and model imaginations. [de

  16. Advanced materials for the optical delay line of frequency pulse modulator on the basis of semiconductor laser

    International Nuclear Information System (INIS)

    Abrarov, S.M.

    1999-01-01

    In the paper some materials which can be sued as an optical delay line of the pulse frequency modulator are considered. The structure and the principle are described as a modulator consisting of a laser diode with two Fabry Perot resonators and an optical wave guide providing a feedback loop. The optical wave guide fulfills the function of delay line and links the two resonators. The pulse sequence of the radiation of the semiconductor laser arises due to failure and recovery of optical generation. The pulse frequency modulation can be carried out by the action of electrical tension field on the electro optic martial of the wave guide. The selection of three electro-optic crystals for making of the optical wave guide of the considered modulator is justified. (author)

  17. Energy levels and far-infrared optical absorption of impurity doped semiconductor nanorings: Intense laser and electric fields effects

    Energy Technology Data Exchange (ETDEWEB)

    Barseghyan, M.G., E-mail: mbarsegh@ysu.am

    2016-11-10

    Highlights: • The electron-impurity interaction on energy levels in nanoring have been investigated. • The electron-impurity interaction on far-infrared absorption have been investigated. • The energy levels are more stable for higher values of electric field. - Abstract: The effects of electron-impurity interaction on energy levels and far-infrared absorption in semiconductor nanoring under the action of intense laser and lateral electric fields have been investigated. Numerical calculations are performed using exact diagonalization technique. It is found that the electron-impurity interaction and external fields change the energy spectrum dramatically, and also have significant influence on the absorption spectrum. Strong dependence on laser field intensity and electric field of lowest energy levels, also supported by the Coulomb interaction with impurity, is clearly revealed.

  18. Control of optical bistability and third-order nonlinearity via tunneling induced quantum interference in triangular quantum dot molecules

    International Nuclear Information System (INIS)

    Tian, Si-Cong; Tong, Cun-Zhu; Zhang, Jin-Long; Shan, Xiao-Nan; Fu, Xi-Hong; Zeng, Yu-Gang; Qin, Li; Ning, Yong-Qiang; Wan, Ren-Gang

    2015-01-01

    The optical bistability of a triangular quantum dot molecules embedded inside a unidirectional ring cavity is studied. The type, the threshold and the hysteresis loop of the optical bistability curves can be modified by the tunneling parameters, as well as the probe laser field. The linear and nonlinear susceptibilities of the medium are also studied to interpret the corresponding results. The physical interpretation is that the tunneling can induce the quantum interference, which modifies the linear and the nonlinear response of the medium. As a consequence, the characteristics of the optical bistability are changed. The scheme proposed here can be utilized for optimizing and controlling the optical switching process

  19. Laser Raman and resonance Raman spectroscopies of natural semiconductor mineral cinnabar, α-HgS, from various mines

    International Nuclear Information System (INIS)

    Gotoshia, Sergo V; Gotoshia, Lamara V

    2008-01-01

    Natural minerals α-HgS from various mines have been studied by laser Raman spectroscopy and resonance Raman spectroscopy. The crystals differ from each other in the content of selenium impurity, included in samples from some mines. Based on the Raman spectra and the factor-group analysis the classification of the first order phonons and then the comparison of the results with the results from other works were carried out. The Raman spectra analysis of minerals from various mines show the selenium impurity gap vibration at 203 cm -1 and 226 cm -1 frequencies, respectively. On the basis of statistical measurements of the Raman spectra one can conclude that impurity frequencies of α-HgS may be generally used for the identification of the mine. Resonance Raman scattering for pure minerals has been studied by a dye laser. Phonon resonance in the indirect semiconductor α-HgS is found to be far more intense than the indirect resonance detected until now in various semiconductors in the proximity of the first indirect band E g , for instance, in GaP. In our opinion, this may be conditioned by cinnabar band structure peculiarities. Low resonance has also been fixed in 'dirty' minerals at the spectral band frequency of 203 cm -1 characterizing gap vibration of isomorphic impurity Se in cinnabar

  20. A novel image encryption algorithm based on synchronized random bit generated in cascade-coupled chaotic semiconductor ring lasers

    Science.gov (United States)

    Li, Jiafu; Xiang, Shuiying; Wang, Haoning; Gong, Junkai; Wen, Aijun

    2018-03-01

    In this paper, a novel image encryption algorithm based on synchronization of physical random bit generated in a cascade-coupled semiconductor ring lasers (CCSRL) system is proposed, and the security analysis is performed. In both transmitter and receiver parts, the CCSRL system is a master-slave configuration consisting of a master semiconductor ring laser (M-SRL) with cross-feedback and a solitary SRL (S-SRL). The proposed image encryption algorithm includes image preprocessing based on conventional chaotic maps, pixel confusion based on control matrix extracted from physical random bit, and pixel diffusion based on random bit stream extracted from physical random bit. Firstly, the preprocessing method is used to eliminate the correlation between adjacent pixels. Secondly, physical random bit with verified randomness is generated based on chaos in the CCSRL system, and is used to simultaneously generate the control matrix and random bit stream. Finally, the control matrix and random bit stream are used for the encryption algorithm in order to change the position and the values of pixels, respectively. Simulation results and security analysis demonstrate that the proposed algorithm is effective and able to resist various typical attacks, and thus is an excellent candidate for secure image communication application.

  1. A broadband electromagnetic energy harvester with a coupled bistable structure

    International Nuclear Information System (INIS)

    Zhu, D; Beeby, S P

    2013-01-01

    This paper investigates a broadband electromagnetic energy harvester with a coupled bistable structure. Both analytical model and experimental results showed that the coupled bistable structure requires lower excitation force to trigger bistable operation than conventional bistable structures. A compact electromagnetic vibration energy harvester with a coupled bistable structure was implemented and tested. It was excited under white noise vibrations. Experimental results showed that the coupled bistable energy harvester can achieve bistable operation with lower excitation amplitude and generate more output power than both conventional bistable and linear energy harvesters under white noise excitation

  2. A bistable mechanism for directional sensing

    International Nuclear Information System (INIS)

    Beta, C; Amselem, G; Bodenschatz, E

    2008-01-01

    We present a generic mechanism for directional sensing in eukaryotic cells that is based on bistable dynamics. As the key feature of this modeling approach, the velocity of trigger waves in the bistable sensing system changes its sign across cells that are exposed to an external chemoattractant gradient. This is achieved by combining a two-component activator/inhibitor system with a bistable switch that induces an identical symmetry breaking for arbitrary gradient input signals. A simple kinetic example is designed to illustrate the dynamics of a bistable directional sensing mechanism in numerical simulations

  3. High-Speed Semiconductor Vertical-Cavity Surface-Emitting Lasers for Optical Data-Transmission Systems (Review)

    Science.gov (United States)

    Blokhin, S. A.; Maleev, N. A.; Bobrov, M. A.; Kuzmenkov, A. G.; Sakharov, A. V.; Ustinov, V. M.

    2018-01-01

    The main problems of providing a high-speed operation semiconductor lasers with a vertical microcavity (so-called "vertical-cavity surface-emitting lasers") under amplitude modulation and ways to solve them have been considered. The influence of the internal properties of the radiating active region and the electrical parasitic elements of the equivalent circuit of lasers are discussed. An overview of approaches that lead to an increase of the cutoff parasitic frequency, an increase of the differential gain of the active region, the possibility of the management of mode emission composition and the lifetime of photons in the optical microcavities, and reduction of the influence of thermal effects have been presented. The achieved level of modulation bandwidth of ˜30 GHz is close to the maximum achievable for the classical scheme of the direct-current modulation, which makes it necessary to use a multilevel modulation format to further increase the information capacity of optical channels constructed on the basis of vertical-cavity surface-emitting lasers.

  4. Stabilization in laser wavelength semiconductor with fiber optical amplifier application doped with erbium

    International Nuclear Information System (INIS)

    Camas, J.; Anzueto, G.; Mendoza, S.; Hernandez, H.; Garcia, C.; Vazquez, R.

    2009-01-01

    In this work, we present a novel electronic design of a DC source, which automatically controls the temperature of a tunable laser. The temperature change in the laser is carried out by the control of DC that circulates through a cooling stage where the laser is set. The laser can be tuned in a wavelength around 1550 nm. Its application is in Erbium Doped Fiber Amplifier (EDFA) in reflective configuration. (Author)

  5. Bistable diverter valve in microfluidics

    Czech Academy of Sciences Publication Activity Database

    Tesař, Václav; Bandulasena, H.C.H.

    2011-01-01

    Roč. 50, č. 5 (2011), s. 1225-1233 ISSN 0723-4864 R&D Projects: GA ČR GA101/07/1499; GA AV ČR IAA200760705 Institutional research plan: CEZ:AV0Z20760514 Keywords : fluidics * bistable diverter valves * pressure-driven microfluidics Subject RIV: BK - Fluid Dynamics Impact factor: 1.735, year: 2011 http://www.springerlink.com/content/x4907p1908151522/

  6. Brain networks underlying bistable perception.

    Science.gov (United States)

    Baker, Daniel H; Karapanagiotidis, Theodoros; Coggan, David D; Wailes-Newson, Kirstie; Smallwood, Jonathan

    2015-10-01

    Bistable stimuli, such as the Necker Cube, demonstrate that experience can change in the absence of changes in the environment. Such phenomena can be used to assess stimulus-independent aspects of conscious experience. The current study used resting state functional magnetic resonance imaging (rs-fMRI) to index stimulus-independent changes in neural activity to understand the neural architecture that determines dominance durations during bistable perception (using binocular rivalry and Necker cube stimuli). Anterior regions of the Superior Parietal Lobule (SPL) exhibited robust connectivity with regions of primary sensorimotor cortex. The strength of this region's connectivity with the striatum predicted shorter dominance durations during binocular rivalry, whereas its connectivity to pre-motor cortex predicted longer dominance durations for the Necker Cube. Posterior regions of the SPL, on the other hand, were coupled to associative cortex in the temporal and frontal lobes. The posterior SPL's connectivity to the temporal lobe predicted longer dominance during binocular rivalry. In conjunction with prior work, these data suggest that the anterior SPL contributes to perceptual rivalry through the inhibition of incongruent bottom up information, whereas the posterior SPL influences rivalry by supporting the current interpretation of a bistable stimulus. Our data suggests that the functional connectivity of the SPL with regions of sensory, motor, and associative cortex allows it to regulate the interpretation of the environment that forms the focus of conscious attention at a specific moment in time. Copyright © 2015. Published by Elsevier Inc.

  7. Lasers

    CERN Document Server

    Milonni, Peter W

    1988-01-01

    A comprehensive introduction to the operating principles and applications of lasers. Explains basic principles, including the necessary elements of classical and quantum physics. Provides concise discussions of various laser types including gas, solid state, semiconductor, and free electron lasers, as well as of laser resonators, diffraction, optical coherence, and many applications including holography, phase conjugation, wave mixing, and nonlinear optics. Incorporates many intuitive explanations and practical examples. Discussions are self-contained in a consistent notation and in a style that should appeal to physicists, chemists, optical scientists and engineers.

  8. Semiconductor laser engineering, reliability and diagnostics a practical approach to high power and single mode devices

    CERN Document Server

    Epperlein, Peter W

    2013-01-01

    This reference book provides a fully integrated novel approach to the development of high-power, single-transverse mode, edge-emitting diode lasers by addressing the complementary topics of device engineering, reliability engineering and device diagnostics in the same book, and thus closes the gap in the current book literature. Diode laser fundamentals are discussed, followed by an elaborate discussion of problem-oriented design guidelines and techniques, and by a systematic treatment of the origins of laser degradation and a thorough exploration of the engineering means to enhance the optical strength of the laser. Stability criteria of critical laser characteristics and key laser robustness factors are discussed along with clear design considerations in the context of reliability engineering approaches and models, and typical programs for reliability tests and laser product qualifications. Novel, advanced diagnostic methods are reviewed to discuss, for the first time in detail in book literature, performa...

  9. Bistable dynamics of a levitated nanoparticle (Presentation Recording)

    Science.gov (United States)

    Ricci, Francesco; Spasenovic, M.; Rica, Raúl A.; Novotny, Lukas; Quidant, Romain

    2015-08-01

    resonance and sensory information processing: a tutorial and review of application" Clinical neurophysiology 115 (2004) 267 [3] M. Platkov, and M. Gruebele, "Periodic and stochastic thermal modulation of protein folding kinetics" J. Chem. Phys. 141 (2014) 035103 [4] T. Tanabe, M. Notomi, S. Mitsugi, A. Shinya and E. Kuramochi. "Fast bistable all-optical switch and memory on a silicon photonic crystal on-chip". Opt. Lett., 30 (2005) 2575 [5] R. L. Badzey and P. Mohanty. "Coherent signal amplification in bistable nanomechanical oscillators by stochastic resonance" Nature, 437 (2005) 995 [6] W. J. Venstra, H. J. R. Westra, and H. S. J. van der Zant. "Stochastic switching of cantilever motion," Nature Communications, 4 (2013) 3624 [7] J. Gieseler, B. Deutsch, R. Quidant, and L. Novotny "Subkelvin parametric feedback cooling of a Laser-Trapped nanoparticle" Phys. Rev. Lett. 109 (2012) 103603 [8] J. Gieseler, M. Spasenović, L. Novotny, and R. Quidant, "Nonlinear Mode Coupling and Synchronization of a Vacuum-Trapped Nanoparticle," Phys. Rev. Lett. 112 (2014) 103603

  10. Study of the spectral width of intermode beats and optical spectrum of an actively mode-locked three-mirror semiconductor laser

    International Nuclear Information System (INIS)

    Zakharyash, Valerii F; Kashirsky, Aleksandr V; Klementyev, Vasilii M; Kuznetsov, Sergei A; Pivtsov, V S

    2005-01-01

    Various oscillation regimes of an actively mode-locked semiconductor laser are studied experimentally. Two types of regimes are found in which the minimal spectral width (∼3.5 kHz) of intermode beats is achieved. The width of the optical spectrum of modes is studied as a function of their locking and the feedback coefficients. The maximum width of the spectrum is ∼3.7 THz. (control of laser radiation parameters)

  11. Conductors, semiconductors and insulators irradiated with short-wavelength free-electron laser

    Czech Academy of Sciences Publication Activity Database

    Krzywinski, J.; Sobierajski, R.; Jurek, M.; Nietubyc, R.; Pelka, J. B.; Juha, Libor; Bittner, Michal; Létal, V.; Vorlíček, Vladimír; Andrejczuk, A.; Feldhaus, J.; Keitel, B.; Saldin, E.; Schneidmiller, E.A.; Treusch, R.; Yurkov, M. V.

    2007-01-01

    Roč. 101, č. 4 (2007), 043107/1-043107/4 ISSN 0021-8979 R&D Projects: GA MŠk 1P04LA235; GA MŠk LC510; GA MŠk(CZ) LC528 Institutional research plan: CEZ:AV0Z10100523 Keywords : free-electron laser * extreme ultraviolet * ablation * laser-matter interaction Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.171, year: 2007

  12. A novel bistable energy harvesting concept

    International Nuclear Information System (INIS)

    Scarselli, G; Nicassio, F; Pinto, F; Ciampa, F; Iervolino, O; Meo, M

    2016-01-01

    Bistable energy harvesting has become a major field of research due to some unique features for converting mechanical energy into electrical power. When properly loaded, bistable structures snap-through from one stable configuration to another, causing large strains and consequently power generation. Moreover, bistable structures can harvest energy across a broad-frequency bandwidth due to their nonlinear characteristics. Despite the fact that snap-through may be triggered regardless of the form or frequency of exciting vibration, the external force must reach a specific snap-through activation threshold value to trigger the transition from one stable state to another. This aspect is a limiting factor for realistic vibration energy harvesting application with bistable devices. This paper presents a novel power harvesting concept for bistable composites based on a ‘lever effect’ aimed at minimising the activation force to cause the snap through by choosing properly the bistable structures’ constraints. The concept was demonstrated with the help of numerical simulation and experimental testing. The results showed that the actuation force is one order of magnitude smaller (3%–6%) than the activation force of conventionally constrained bistable devices. In addition, it was shown that the output voltage was higher than the conventional configuration, leading to a significant increase in power generation. This novel concept could lead to a new generation of more efficient bistable energy harvesters for realistic vibration environments. (paper)

  13. Diversity and functional properties of bistable pigments.

    Science.gov (United States)

    Tsukamoto, Hisao; Terakita, Akihisa

    2010-11-01

    Rhodopsin and related opsin-based pigments, which are photosensitive membrane proteins, have been extensively studied using a wide variety of techniques, with rhodopsin being the most understood G protein-coupled receptor (GPCR). Animals use various opsin-based pigments for vision and a wide variety of non-visual functions. Many functionally varied pigments are roughly divided into two kinds, based on their photoreaction: bistable and monostable pigments. Bistable pigments are thermally stable before and after photo-activation, but monostable pigments are stable only before activation. Here, we review the diversity of bistable pigments and their molecular characteristics. We also discuss the mechanisms underlying different molecular characteristics of bistable and monostable pigments. In addition, the potential of bistable pigments as a GPCR model is proposed.

  14. Phase noise reduction by self-phase locking in semiconductor lasers using phase conjugate feedback

    DEFF Research Database (Denmark)

    Petersen, Lykke; Gliese, Ulrik Bo; Nielsen, Torben Nørskov

    1994-01-01

    noise takes a finite-low value corresponding to a state of first-order self-phase locking of the laser. As a result, the spectral shape of the laser signal does not remain Lorentzian but collapses around the carrier to a delta function with a close to carrier noise level of less than -137 d...

  15. Self-induced frequency scanning and distributed Bragg reflection in semiconductor lasers with phase-conjugate feedback

    Energy Technology Data Exchange (ETDEWEB)

    Cronin-Golomb; Yariv

    1986-07-01

    A GaA1As semiconductor laser with feedback from a barium titanate photorefractive ring passive phase-conjugate mirror can be made to perform repeating or nonrepeating frequency scans over a 10-nm range toward either the blue or the red. The direction of scanning and whether the scans repeat may be controlled by adjusting the overlap of the interaction beams in the crystal. This overlap region may be adjusted so that the diode frequency spectrum, originally occupying about 10 longitudinal modes, scans and narrows as the conjugate signal builds up, coming to rest often in one, but sometimes two or three, longitudinal modes as a result of self-generated distributed-feedback effects. Also reported similar effects caused by feedback from the total-internal-reflection passive phase-conjugate mirror. The alignment-control mechanism of the ring mirror is, however, not available in this case.

  16. Self-induced frequency scanning and distributed Bragg reflection in semiconductor lasers with phase-conjugate feedback

    Energy Technology Data Exchange (ETDEWEB)

    Cronin-Golomb, M.; Yariv, A.

    1986-07-01

    A GaAlAs semiconductor laser with feedback from a barium titanate photorefractive ring passive phase-conjugate mirror can be made to perform repeating or nonrepeating frequency scans over a 10-nm range toward either the blue or the red. The direction of scanning and whether the scans repeat may be controlled by adjusting the overlap of the interaction beams in the crystal. This overlap region may be adjusted so that the diode frequency spectrum, originally occupying about 10 longitudinal modes, scans and narrows as the conjugate signal builds up, coming to rest often in one, but sometimes two or three, longitudinal modes as a result of self-generated distributed-feedback effects. We also report similar effects caused by feedback from the total-internal-reflection passive phase-conjugate mirror. The alignment-control mechanism of the ring mirror is, however, not available in this case.

  17. Self-induced frequency scanning and distributed bragg reflection in semiconductor lasers with phase-conjugate feedback

    Science.gov (United States)

    Cronin-Golomb, Mark; Yariv, Amnon

    1986-07-01

    A GaAlAs semiconductor laser with feedback from a barium titanate photorefractive ring passive phase-conjugate mirror can be made to perform repeating or nonrepeating frequency scans over a 10-nm range toward either the blue or the red. The direction of scanning and whether the scans repeat may be controlled by adjusting the overlap of the interaction beams in the crystal. This overlap region may be adjusted so that the diode frequency spectrum, originally occupying about 10 longitudinal modes, scans and narrows as the conjugate signal builds up, coming to rest often in one, but sometimes two or three, longitudinal modes as a result of self-generated distributed-feedback effects. We also report similar effects caused by feedback from the total-internal-reflection passive phase-conjugate mirror. The alignment-control mechanism of the ring mirror is, however, not available in this case.

  18. Measurement of laser activated electron tunneling from semiconductor zinc oxide to adsorbed organic molecules by a matrix assisted laser desorption ionization mass spectrometer

    International Nuclear Information System (INIS)

    Zhong Hongying; Fu Jieying; Wang Xiaoli; Zheng Shi

    2012-01-01

    Highlights: ► Irradiation of photons with energies more than the band gap generates electron–hole pairs. ► Electron tunneling probability is dependent on the electron mobility. ► Tunneling electrons are captured by charge deficient atoms. ► Unpaired electrons induce cleavages of chemical bonds. - Abstract: Measurement of light induced heterogeneous electron transfer is important for understanding of fundamental processes involved in chemistry, physics and biology, which is still challenging by current techniques. Laser activated electron tunneling (LAET) from semiconductor metal oxides was observed and characterized by a MALDI (matrix assisted laser desorption ionization) mass spectrometer in this work. Nanoparticles of ZnO were placed on a MALDI sample plate. Free fatty acids and derivatives were used as models of organic compounds and directly deposited on the surface of ZnO nanoparticles. Irradiation of UV laser (λ = 355 nm) with energy more than the band gap of ZnO produces ions that can be detected in negative mode. When TiO 2 nanoparticles with similar band gap but much lower electron mobility were used, these ions were not observed unless the voltage on the sample plate was increased. The experimental results indicate that laser induced electron tunneling is dependent on the electron mobility and the strength of the electric field. Capture of low energy electrons by charge-deficient atoms of adsorbed organic molecules causes unpaired electron-directed cleavages of chemical bonds in a nonergodic pathway. In positive detection mode, electron tunneling cannot be observed due to the reverse moving direction of electrons. It should be able to expect that laser desorption ionization mass spectrometry is a new technique capable of probing the dynamics of electron tunneling. LAET offers advantages as a new ionization dissociation method for mass spectrometry.

  19. Controlling steady-state and dynamical properties of atomic optical bistability

    CERN Document Server

    Joshi, Amitabh

    2012-01-01

    This book provides a comprehensive introduction to the theoretical and experimental studies of atomic optical bistability and multistability, and their dynamical properties in systems with two- and three-level inhomogeneously-broadened atoms inside an optical cavity. By making use of the modified linear absorption and dispersion, as well as the greatly enhanced nonlinearity in the three-level electromagnetically induced transparency system, the optical bistablity and efficient all-optical switching can be achieved at relatively low laser powers, which can be well controlled and manipulated. Un

  20. Bistability By Self-Reflection In A Saturable Absorber

    Science.gov (United States)

    Roso-Franco, Luis

    1987-01-01

    Propagation of laser light through a saturable absorber is theoretically studied. Computed steady state solutions of the Maxwell equations describing the unidimensional propagation of a plane monochromatic wave without introducing the slowly-varying envelope approximation are presented showing how saturation effects can influence the absorption of the field. At a certain range of refractive index and extintion coefficients, computed solutions display a very susprising behaviour, and a self-reflected wave appears inside the absorber. This can be useful for a new kind of biestable device, similar to a standard bistable cavity but with the back mirror self-induced by the light.

  1. Low SWaP Semiconductor Laser Transmitter Modules For ASCENDS Mission Applications

    Science.gov (United States)

    Prasad, Narasimha S.; Rosiewicz, Alex; Coleman, Steven M.

    2012-01-01

    The National Research Council's (NRC) Decadal Survey (DS) of Earth Science and Applications from Space has identified the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) as an important atmospheric science mission. NASA Langley Research Center, working with its partners, is developing fiber laser architecture based intensity modulated CW laser absorption spectrometer for measuring XCO2 in the 1571 nm spectral band. In support of this measurement, remote sensing of O2 in the 1260 nm spectral band for surface pressure measurements is also being developed. In this paper, we will present recent progress made in the development of advanced transmitter modules for CO2 and O2 sensing. Advanced DFB seed laser modules incorporating low-noise variable laser bias current supply and low-noise variable temperature control circuit have been developed. The 1571 nm modules operate at >80 mW and could be tuned continuously over the wavelength range of 1569-1574nm at a rate of 2 pm/mV. Fine tuning was demonstrated by adjusting the laser drive at a rate of 0.7 pm/mV. Heterodyne linewidth measurements have been performed showing linewidth 200 kHz and frequency jitter 75 MHz. In the case of 1260 nm DFB laser modules, we have shown continuous tuning over a range of 1261.4 - 1262.6 nm by changing chip operating temperature and 1261.0 - 1262.0 nm by changing the laser diode drive level. In addition, we have created a new laser package configuration which has been shown to improve the TEC coefficient of performance by a factor of 5 and improved the overall efficiency of the laser module by a factor of 2.

  2. Stability of period-one (P1) oscillations generated by semiconductor lasers subject to optical injection or optical feedback.

    Science.gov (United States)

    Lin, Lyu-Chih; Liu, Ssu-Hsin; Lin, Fan-Yi

    2017-10-16

    We study the stability of period-one (P1) oscillations experimentally generated by semiconductor lasers subject to optical injection (OI) and by those subject to optical feedback (OF). With unique advantages of broad frequency tuning range and large sideband rejection ratio, P1 oscillations can be useful in applications such as photonic microwave generation, radio-over-fiber communication, and laser Doppler velocimeter. The stability of the P1 oscillations is critical for these applications, which can be affected by spontaneous emission and fluctuations in both temperature and injection current. Although linewidths of P1 oscillations generated by various schemes have been reported, the mechanisms and roles which each of the OI and the OF play have however not been investigated in detail. To characterize the stability of the P1 oscillations generated by the OI and the OF schemes, we measure the linewidths and linewidth reduction ratios (LRRs) of the P1 oscillations. The OF scheme has a narrowest linewidth of 0.21 ± 0.03 MHz compared to 4.7 ± 0.6 MHz in the OI scheme. In the OF scheme, a much larger region of LRRs higher than 90% is also found. The superior stability of the OF scheme is benefited by the fact that the P1 oscillations in the OF scheme are originated from the undamped relaxation oscillation of a single laser and can be phase-locked to one of its external cavity modes, whereas those in the OI scheme come from two independent lasers which bear no phase relation. Moreover, excess P1 linewidth broadening in the OI scheme caused by fluctuation in injection parameters associated with frequency jitter and relative intensity noise (RIN) is also minimized in the OF scheme.

  3. A broadband electromagnetic energy harvester with a coupled bistable structure

    OpenAIRE

    Zhu, Dibin; Beeby, Steve

    2013-01-01

    This paper investigates a broadband electromagnetic energy harvester with a coupled bistable structure. Both analytical model and experimental results showed that the coupled bistable structure requires lower excitation force to trigger bistable operation than conventional bistable structures. A compact electromagnetic vibration energy harvester with a coupled bistable structure was implemented and tested. It was excited under white noise vibrations. Experimental results showed that the coupl...

  4. Electronic defect levels in continuous wave laser annealed silicon metal oxide semiconductor devices

    Science.gov (United States)

    Cervera, M.; Garcia, B. J.; Martinez, J.; Garrido, J.; Piqueras, J.

    1988-09-01

    The effect of laser treatment on the bulk and interface states of the Si-SiO2 structure has been investigated. The annealing was performed prior to the gate metallization using a continuous wave Ar+ laser. For low laser powers the interface state density seems to decrease slightly in comparison with untreated samples. However, for the highest irradiating laser powers a new bulk level at 0.41 eV above the valence band with concentrations up to 1015 cm-3 arises probably due to the electrical activation of the oxygen diluted in the Czochralski silicon. Later postmetallization annealings reduce the interface state density to values in the 1010 cm-2 eV-1 range but leave the concentration of the 0.41-eV center nearly unchanged.

  5. Theoretical Modeling of Intensity Noise in InGaN Semiconductor Lasers

    Directory of Open Access Journals (Sweden)

    Moustafa Ahmed

    2014-01-01

    Full Text Available This paper introduces modeling and simulation of the noise properties of the blue-violet InGaN laser diodes. The noise is described in terms of the spectral properties of the relative intensity noise (RIN. We examine the validity of the present noise modeling by comparing the simulated results with the experimental measurements available in literature. We also compare the obtained noise results with those of AlGaAs lasers. Also, we examine the influence of gain suppression on the quantum RIN. In addition, we examine the changes in the RIN level when describing the gain suppression by the case of inhomogeneous spectral broadening. The results show that RIN of the InGaN laser is nearly 9 dB higher than that of the AlGaAs laser.

  6. Optimal operating conditions for external cavity semiconductor laser optical chaos communication system

    International Nuclear Information System (INIS)

    Priyadarshi, S; Pierce, I; Hong, Y; Shore, K A

    2012-01-01

    In optical chaos communications a message is masked in the noise-like broadband output of a chaotic transmitter laser, and message recovery is enabled through the synchronization of the transmitter and the (chaotic) receiver laser. Key issues are to identify the laser operating conditions which provide the highest quality synchronization conditions and those which provide optimized message extraction. In general such operating conditions are not coincident. In this paper numerical simulations are performed with the aim of identifying a regime of operation where the highest quality synchronization and optimizing message extraction efficiency are achieved simultaneously. Use of such an operating regime will facilitate practical deployment of optical chaos communications systems without the need for re-adjustment of laser operating conditions in the field. (paper)

  7. On the mechanisms governing the repetition rate of mode-locked semiconductor lasers

    DEFF Research Database (Denmark)

    Mulet, Josep; Mørk, Jesper

    2004-01-01

    We investigate the mechanisms influencing the synchronization locking range of mode-locked lasers. We find that changes in repetition rates can be accomodated through a joint interplay of dispersion and pulse shaping effects....

  8. Packaging-induced failure of semiconductor lasers and optical telecommunications components

    Energy Technology Data Exchange (ETDEWEB)

    Sharps, J.A. [Corning Inc., NY (United States)

    1996-12-31

    Telecommunications equipment for field deployment generally have specified lifetimes of > 100,000 hr. To achieve this high reliability, it is common practice to package sensitive components in hermetic, inert gas environments. The intent is to protect components from particulate and organic contamination, oxidation, and moisture. However, for high power density 980 nm diode lasers used in optical amplifiers, the authors found that hermetic, inert gas packaging induced a failure mode not observed in similar, unpackaged lasers. They refer to this failure mode as packaging-induced failure, or PIF. PIF is caused by nanomole amounts of organic contamination which interact with high intensity 980 nm light to form solid deposits over the emitting regions of the lasers. These deposits absorb 980 nm light, causing heating of the laser, narrowing of the band gap, and eventual thermal runaway. The authors have found PIF is averted by packaging with free O{sub 2} and/or a getter material that sequesters organics.

  9. Short pulse generation in a passively mode-locked photonic crystal semiconductor laser

    DEFF Research Database (Denmark)

    Heuck, Mikkel; Blaaberg, Søren; Mørk, Jesper

    2010-01-01

    We present a new type of passively mode-locked laser with quantum wells embedded in photonic crystal waveguides operating in the slow light regime, which is capable of emitting sub picosecond pulses with widely controllable properties......We present a new type of passively mode-locked laser with quantum wells embedded in photonic crystal waveguides operating in the slow light regime, which is capable of emitting sub picosecond pulses with widely controllable properties...

  10. Phosphorus-free mode-locked semiconductor laser with emission wavelength 1550 nm

    Science.gov (United States)

    Kolodeznyi, E. S.; Novikov, I. I.; Babichev, A. V.; Kurochkin, A. S.; Gladyshev, A. G.; Karachinsky, L. Ya; Gadzhiev, I. M.; Buyalo, M. S.; Usikova, A. A.; Ilynskaya, N. D.; Bougrov, V. E.; Egorov, A. Yu

    2017-11-01

    We have fabricated passive mode-locked laser diodes based on strained InGaAlAs/InGaAs/InP heterostructures with crystal lattice mismatch parameter of +1.0 % between quantum well and barrier. The laser with temperature stabilization at 18 °C was demonstrated 10.027 GHz optical pulse repetition rate with 6 ps pulse duration time. Timing jitter of optical pulses in mode-locked regime was 0.145 ps.

  11. High-resolution bistable nematic liquid crystal device realized on orientational surface patterns

    International Nuclear Information System (INIS)

    Kim, Jong-Hyun; Yoneya, Makoto; Yokoyama, Hiroshi

    2003-01-01

    The four-fold symmetry of a checkerboard-like surface alignment consisted of square domains arrived at the macroscopic orientational bistability of nematic liquid crystals. Switching between the two orientations took place with an appropriate electric field. Here the threshold field of bistable switching decreased as temperature increased, and the light could heat only the selected region in the cell including a light-absorbing medium. Irradiating the laser concurrently with an electric field, we addressed a selected region in the alignment pattern without the disturbance of neighboring regions. Extending this process, we realized an extremely fine bistable device of nematic liquid crystal with a pixel size down to about 2 μm

  12. Effect of semiconductor GaAs laser irradiation on pain perception in mice

    Energy Technology Data Exchange (ETDEWEB)

    Zarkovic, N.; Manev, H.; Pericic, D.; Skala, K.; Jurin, M.; Persin, A.; Kubovic, M.

    1989-01-01

    The influence of subacute exposure (11 exposures within 16 days) of mice to the low power (GaAs) semiconductive laser-stimulated irradiation on pain perception was investigated. The pain perception was determined by the latency of foot-licking or jumping from the surface of a 53 degrees C hot plate. Repeated hot-plate testing resulted in shortening of latencies in both sham- and laser-irradiated mice. Laser treatment (wavelength, 905 nm; frequency, 256 Hz; irradiation time, 50 sec; pulse duration, 100 nsec; distance, 3 cm; peak irradiance, 50 W/cm2 in irradiated area; and total exposure, 0.41 mJ/cm2) induced further shortening of latencies, suggesting its stimulatory influence on pain perception. Administration of morphine (20 mg/kg) prolonged the latency of response to the hot plate in both sham- and laser-irradiated mice. This prolongation tended to be lesser in laser-irradiated animals. Further investigations are required to elucidate the mechanism of the observed effect of laser.

  13. Phase dependence of optical bistability and multistability in a four-level quantum system near a plasmonic nanostructure

    International Nuclear Information System (INIS)

    Asadpour, Seyyed Hossein; Rahimpour Soleimani, H.

    2016-01-01

    The optical bistability and multistability properties of a four-level quantum system near a plasmonic nanostructure embedded in a unidirectional ring cavity are studied theoretically. Two orthogonal circularly polarized laser fields with the same frequency, different phases and electric fields amplitude are interacted by four-level quantum system. It is found that in the presence of the plasmonic nanostructure, the bistable behaviors related to one of the laser fields propagating through the unidirectional ring cavity can be modified by relative phase and amplitude control of another laser fields. Our obtained results show that the optical bistability can be converted into the optical multistability by varying the value of distance between the quantum system and the surface of the plasmonic nanostructure. Moreover, it is shown that under specific condition related to the distance, the lasing without population inversion can be obtained

  14. Phase dependence of optical bistability and multistability in a four-level quantum system near a plasmonic nanostructure

    Energy Technology Data Exchange (ETDEWEB)

    Asadpour, Seyyed Hossein; Rahimpour Soleimani, H., E-mail: Rahimpour@guilan.ac.ir [Computational Nanophysics Laboratory (CNL), Department of Physics, University of Guilan, Rasht (Iran, Islamic Republic of)

    2016-01-14

    The optical bistability and multistability properties of a four-level quantum system near a plasmonic nanostructure embedded in a unidirectional ring cavity are studied theoretically. Two orthogonal circularly polarized laser fields with the same frequency, different phases and electric fields amplitude are interacted by four-level quantum system. It is found that in the presence of the plasmonic nanostructure, the bistable behaviors related to one of the laser fields propagating through the unidirectional ring cavity can be modified by relative phase and amplitude control of another laser fields. Our obtained results show that the optical bistability can be converted into the optical multistability by varying the value of distance between the quantum system and the surface of the plasmonic nanostructure. Moreover, it is shown that under specific condition related to the distance, the lasing without population inversion can be obtained.

  15. Layer-by-layer modification of thin-film metal-semiconductor multilayers with ultrashort laser pulses

    Science.gov (United States)

    Romashevskiy, S. A.; Tsygankov, P. A.; Ashitkov, S. I.; Agranat, M. B.

    2018-05-01

    The surface modifications in a multilayer thin-film structure (50-nm alternating layers of Si and Al) induced by a single Gaussian-shaped femtosecond laser pulse (350 fs, 1028 nm) in the air are investigated by means of atomic-force microscopy (AFM), scanning electron microscopy (SEM), and optical microscopy (OM). Depending on the laser fluence, various modifications of nanometer-scale metal and semiconductor layers, including localized formation of silicon/aluminum nanofoams and layer-by-layer removal, are found. While the nanofoams with cell sizes in the range of tens to hundreds of nanometers are produced only in the two top layers, layer-by-layer removal is observed for the four top layers under single pulse irradiation. The 50-nm films of the multilayer structure are found to be separated at their interfaces, resulting in a selective removal of several top layers (up to 4) in the form of step-like (concentric) craters. The observed phenomenon is associated with a thermo-mechanical ablation mechanism that results in splitting off at film-film interface, where the adhesion force is less than the bulk strength of the used materials, revealing linear dependence of threshold fluences on the film thickness.

  16. Nonvolatile memory characteristics in metal-oxide-semiconductors containing metal nanoparticles fabricated by using a unique laser irradiation method

    International Nuclear Information System (INIS)

    Yang, JungYup; Yoon, KapSoo; Kim, JuHyung; Choi, WonJun; Do, YoungHo; Kim, ChaeOk; Hong, JinPyo

    2006-01-01

    Metal-oxide-semiconductor (MOS) capacitors with metal nanoparticles (Co NP) were successfully fabricated by utilizing an external laser exposure technique for application of non-volatile memories. Images of high-resolution transmission electron microscopy reveal that the spherically shaped Co NP are clearly embedded in the gate oxide layer. Capacitance-voltage measurements exhibit typical charging and discharging effects with a large flat-band shift. The effects of the tunnel oxide thickness and the different tunnel materials are analyzed using capacitance-voltage and retention characteristics. In addition, the memory characteristics of the NP embedded in a high-permittivity material are investigated because the thickness of conventionally available SiO 2 gates is approaching the quantum tunneling limit as devices are scaled down. Finally, the suitability of NP memory devices for nonvolatile memory applications is also discussed. The present results suggest that our unique laser exposure technique holds promise for the NP formation as floating gate elements in nonvolatile NP memories and that the quality of the tunnel oxide is very important for enhancing the retention properties of nonvolatile memory.

  17. Transcriptional delay stabilizes bistable gene networks.

    Science.gov (United States)

    Gupta, Chinmaya; López, José Manuel; Ott, William; Josić, Krešimir; Bennett, Matthew R

    2013-08-02

    Transcriptional delay can significantly impact the dynamics of gene networks. Here we examine how such delay affects bistable systems. We investigate several stochastic models of bistable gene networks and find that increasing delay dramatically increases the mean residence times near stable states. To explain this, we introduce a non-Markovian, analytically tractable reduced model. The model shows that stabilization is the consequence of an increased number of failed transitions between stable states. Each of the bistable systems that we simulate behaves in this manner.

  18. All-optical NRZ-to-RZ data format conversion with optically injected laser diode or semiconductor optical amplifier

    Science.gov (United States)

    Lin, Gong-Ru; Chang, Yung-Cheng; Yu, Kun-Chieh

    2006-09-01

    By injecting the optical NRZ data into a Fabry-Perot laser diode (FPLD) synchronously modulated at below threshold condition or a semiconductor optical amplifier (SOA) gain-depleted with a backward injected clock stream, the all-optical non-return to zero (NRZ) to return-to-zero (RZ) format conversion of a STM-64 date-stream for synchronous digital hierarchy (SDH) or an OC-192 data stream for synchronous optical network (SONET) in high-speed fiber-optic communication link can be performed. Without the assistance of any complicated RF electronic circuitry, the output RZ data-stream at bit rate of up to 10 Gbit/s is successfully transformed in the optically NRZ injection-locked FPLD, in which the incoming NRZ data induces gain-switching of the FPLD without DC driving current or at below threshold condition. A power penalty of 1.2 dB is measured after NRZ-to-RZ transformation in the FPLD. Alternatively, the all-optical 10Gbits/s NRZ-to-RZ format conversion can also be demonstrated in a semiconductor optical amplifier under a backward dark-optical-comb injection with its duty-cycle 70%, which is obtained by reshaping from the received data clock at 10 GHz. The incoming optical NRZ data-stream is transformed into a pulsed RZ data-stream with its duty-cycle, rms timing jitter, and conversion gain of 15%, 4ps, and 3dB, respectively. In contrast to the FPLD, the SOA based NRZ-to-RZ converter exhibits an enhanced extinction ratio from 7 to 13 dB, and BER of 10 -13 at -18.5 dBm. In particular, the power penalty of the received RZ data-stream has greatly improved by 5 dB as compared to that obtained from FPLD.

  19. UV laser drilling of SiC for semiconductor device fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Krueger, Olaf; Schoene, Gerd; Wernicke, Tim; John, Wilfred; Wuerfl, Joachim; Traenkle, Guenther [Ferdinand-Braun-Institut fuer Hoechstfrequenztechnik, Gustav-Kirchhoff-Str. 4, 12489 Berlin (Germany)

    2007-04-15

    Pulsed UV laser processing is used to drill micro holes in silicon carbide (SiC) wafers supporting AlGaN/GaN transistor structures. Direct laser ablation using nanosecond pulses has been proven to provide an efficient way to create through and blind holes in 400 {mu}m thick SiC. When drilling through, openings in the front pads are formed, while blind holes stop {approx}40 {mu}m before the backside and were advanced to the electrical contact pad by subsequent plasma etching without an additional mask. Low induction connections (vias) between the transistor's source pads and the ground on the backside were formed by metallization of the holes. Micro vias having aspect ratios of 5-6 have been processed in 400 {mu}m SiC. The process flow from wafer layout to laser drilling is available including an automated beam alignment that allows a positioning accuracy of {+-}1 {mu}m with respect to existing patterns on the wafer. As proven by electrical dc and rf measurements the laser-assisted via technologies have successfully been implemented into fabrication of AlGaN/GaN high-power transistors.

  20. Semiconductor Deposition and Etching Interactions of Laser-Generated Translationally Hot Atoms and Radicals

    Science.gov (United States)

    1991-05-01

    fluorescence," J. Chem. Phys. 86, 6731 (1987). J. E. Smedley , H. K. Haugen and S. R. Leone, "Collision-induced dissociation of laser- excited Br 2 [B3Fl(Ou... Robert J. Levis, postdoc, presently Assistant Professor of Chemistry, Wayne State University. Lisa M. Cousins, graduate student, Ph.D. 1989, presently

  1. Theory and experiment of laterally coupled multi-longitudinal-mode semiconductor lasers

    NARCIS (Netherlands)

    Lenstra, D.; Yousefi, M.; Barsella, A.; Morthier, G.; Baets, R.G.F.; McMurtry, S.; Vilcot, J.-P.

    2003-01-01

    This report presents simulations and measurements of multimode dynamics in the twin-stripe laser resulting from complicated gain competition effects. The theory is based on a novel multi-longitudinal rate equations model, while accounting for both coherent and incoherent lateral coupling between the

  2. Photo-Machining of Semiconductor Related Materials with Femtosecond Laser Ablation and Characterization of Its Properties

    Science.gov (United States)

    Yokotani, Atushi; Mizuno, Toshio; Mukumoto, Toru; Kawahara, Kousuke; Ninomiya, Takahumi; Sawada, Hiroshi; Kurosawa, Kou

    We have analyzed the drilling process with femtosecond laser on the silicon surface in order to investigate a degree of thermal effect during the dicing process of the very thin silicon substrate. A regenerative amplified Ti:Al2O3 laser (E= 30˜500 μJ/pulse, τ= 200 fs, λ= 780 nm, f= 10 Hz) was used and focused onto a 50 μm-thick silicon sample. ICCD (Intensified Charge coupled Device) camera with a high-speed gate of 5 ns was utilized to take images of processing hole. First, we investigated the dependence of laser energy on the speed of the formation of the drilled hole. As a result, it was found that the lager the energy, the slower the speed of the formation under the minimum hole was obtained. Consequently, in the case of defocused condition, even when the smaller the energy density was used, the very slow speed of formation and the much lager thermal effects are simultaneously observed. So we can say that the degree of the thermal effects is not simply related to energy density of the laser but strongly related to the speed of the formation, which can be measured by the ICCD camera. The similar tendency was also obtained for other materials, which are important for the fabrication of ICs (Al, Cu, SiO2 and acrylic resin).

  3. Transient changes of optical properties in semiconductors in response to femtosecond laser pulses

    Czech Academy of Sciences Publication Activity Database

    Tkachenko, V.; Medvedev, Nikita; Ziaja, B.

    2016-01-01

    Roč. 6, č. 9 (2016), 1-12, č. článku 238. ISSN 2076-3417 Institutional support: RVO:68378271 Keywords : free-electron lasers * transient optical properties Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.679, year: 2016

  4. Stabilization of the Absolute Frequency and Phase of a Compact, Low Jitter Modelocked Semiconductor Diode Laser

    National Research Council Canada - National Science Library

    Delfyett, Peter J., Jr

    2005-01-01

    .... This work represents, to our knowledge, the first stabilized modelocked diode laser using PDH that achieves both supermode elimination and optical frequency comb stabilization. The resulting optical comb source may be useful for advanced RF imaging radar for optical sampling in ADC or in novel waveform generation (DAC's).

  5. Fabrication and characterization of semiconductor lasers of Pb1-x Snx Te

    International Nuclear Information System (INIS)

    Abramof, E.; Ferreira, S.O.; Bandeira, I.N.

    1987-07-01

    The fabrication and characterization of PbTe homostructure diode-lasers are described. The threshold current density is in the range between 2.5 and 10 KA/cm 2 and the factors that lead to the device degradation are discussed. (author) [pt

  6. Optical bistability and multistability driven by external magnetic field in a dielectric slab doped with nanodiamond nitrogen vacancy centres

    Science.gov (United States)

    Nasehi, R.; Norouzi, F.

    2016-08-01

    The theoretical investigation of controlling the optical bistability (OB) and optical multistability (OM) in a dielectric medium doped with nanodiamond nitrogen vacancy centres under optical excitation are reported. The shape of the OB curve from dielectric slab can be tuned by changing the external magnetic field and polarization of the control beam. The effect of the intensity of the control laser field and the frequency detuning of probe laser field on the OB and OM behaviour are also discussed in this paper. The results obtained can be used for realizing an all-optical bistable switching or development of nanoelectronic devices.

  7. Possible hysteresis loops of resonatorless optical bistability

    International Nuclear Information System (INIS)

    Nguyen Ba An; Le Thi Cat Tuong.

    1990-05-01

    We qualitatively show that hysteresis loops of intrinsic optical bistability phenomena without any additional feedback may be of various shapes including those of a butterfly and a three-winged bow. (author). 15 refs, 4 figs

  8. Space charge effects and electronic bistability

    International Nuclear Information System (INIS)

    Ruffini, A.; Strumia, F.; Tommasi, O.

    1996-01-01

    The excitation of metastable states in an atomic beam apparatus by means of electron collision is a widespread technique. The authors have observed a large bistable behaviour in apparatus designed to provide an intense and collimated beam of metastable helium by excitation with orthogonally impinging electrons. This bistable behaviour largely affects the efficiency of the apparatus and is therefore worth of being carefully investigated. The apparatus has an electrode configuration equivalent to that of a tetrode valve with large intergrid distances. The bistability consists in a hysteresis cycle in the curve of the anode current vs. grid voltage. Experimental measurements, supported by a simple theoretical model and by numerical simulation, stress out the crucial role played by space charge effects for the onset of bistability. A comparison with previous observations of this phenomenon is given. Spontaneous current oscillations with various shapes have been recorded in one of the two curves of the hysteresis cycle

  9. Bistable fluidic valve is electrically switched

    Science.gov (United States)

    Fiet, O.; Salvinski, R. J.

    1970-01-01

    Bistable control valve is selectively switched by direct application of an electrical field to divert fluid from one output channel to another. Valve is inexpensive, has no moving parts, and operates on fluids which are relatively poor electrical conductors.

  10. Selective laser-induced photochemical dry etching of semiconductors controlled by ion-bombardment-induced damage

    International Nuclear Information System (INIS)

    Ashby, C.I.H.; Myers, D.R.; Vook, F.L.

    1987-01-01

    When a photochemical dry etching process requires direct participation of photogenerated carriers in the chemical reaction, it is sensitive to the electronic properties of the semiconductor. For such solid-excitation-based dry etching processes, the balance between reaction and carrier recombination rates determines the practical utility of a particular reaction for device fabrication. The distance from the surface at which the photocarriers are generated by light adsorption is determined by the absorption coefficient. In the absence of an external bias potential, only those carriers formed within a diffusion length of the surface space-charge region will have an opportunity to drive the dry etching reaction. When the absorption coefficient is high, most of the photons generate carriers within a diffusion length from the surface space-charge region, and the etching rate is largely determined by the balance between the rate of the carrier-driven reaction and the surface recombination velocity. When the recombination rate of free carriers in the bulk of the semiconductor is high, the effective diffusion length is reduced and fewer of the carriers generated in the subsurface region ever reach the surface. An important effect of ion bombardment is the creation of many lattice defects that increase the rate of recombination of electrons and holes. When a sufficient number of defects, which act as recombination sites, are formed during ion implantation, the recombination of photogenerated carriers at these defects in the subsurface region can greatly reduce the number of carriers which can reach the surface and drive a photochemical etching reaction

  11. Origami Mechanics: Bistability and Isometries

    Science.gov (United States)

    Adda-Bedia, Mokhtar; Lechenault, Frederic; Morphogenesis; multiscale phenomena Team

    2015-03-01

    Origami structures are usually seen as assemblies of rigid faces articulated around creases with hinge-like behaviour. Their deployment and degrees of freedom are purely kinematic, resulting only from the geometry of the crease network. However, in real folded structures, the base material can deform outside the creases. In such situations, face bending competes with crease actuation in a morphogenetic way. In order to rationalise this interplay, we investigate the mechanical behaviour of an infinite sheet on which one or more straight creases meet at a single vertex. We find that these structures generically exhibit bistability, in the sense that they can snap through from one metastable configuration to another. Furthermore, we uncover a new class of isometry of the plane, which corresponds to metastable states of a creased sheet for which the hoop stress vanishes, an instability mechanism that is also responsible for the wrinkling of thin plates.

  12. GABA shapes the dynamics of bistable perception.

    Science.gov (United States)

    van Loon, Anouk M; Knapen, Tomas; Scholte, H Steven; St John-Saaltink, Elexa; Donner, Tobias H; Lamme, Victor A F

    2013-05-06

    Sometimes, perception fluctuates spontaneously between two distinct interpretations of a constant sensory input. These bistable perceptual phenomena provide a unique window into the neural mechanisms that create the contents of conscious perception. Models of bistable perception posit that mutual inhibition between stimulus-selective neural populations in visual cortex plays a key role in these spontaneous perceptual fluctuations. However, a direct link between neural inhibition and bistable perception has not yet been established experimentally. Here, we link perceptual dynamics in three distinct bistable visual illusions (binocular rivalry, motion-induced blindness, and structure from motion) to measurements of gamma-aminobutyric acid (GABA) concentrations in human visual cortex (as measured with magnetic resonance spectroscopy) and to pharmacological stimulation of the GABAA receptor by means of lorazepam. As predicted by a model of neural interactions underlying bistability, both higher GABA concentrations in visual cortex and lorazepam administration induced slower perceptual dynamics, as reflected in a reduced number of perceptual switches and a lengthening of percept durations. Thus, we show that GABA, the main inhibitory neurotransmitter, shapes the dynamics of bistable perception. These results pave the way for future studies into the competitive neural interactions across the visual cortical hierarchy that elicit conscious perception. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Structure, stability properties, and nonlinear dynamics of lateral modes of a broad area semiconductor laser

    DEFF Research Database (Denmark)

    Blaaberg, Søren

    2007-01-01

    Bred-areal halvlederlasere er kompakte lasere designet til at levere høj udgangseffekt (>1 Watt). Den høje effekt opnås ved at gøre laserens aktive område bredt (>100 mikrometer) samt laserspejlene endnu bredere. I det aktive område pumpes laseren elektrisk. Langs laserens ene tværstillede akse l...

  14. High brightness photonic band crystal semiconductor lasers in the passive mode locking regime

    Energy Technology Data Exchange (ETDEWEB)

    Rosales, R.; Kalosha, V. P.; Miah, M. J.; Bimberg, D. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany); Posilović, K. [Institut für Festkörperphysik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany); PBC Lasers GmbH, Hardenbergstrasse 36, 10623 Berlin (Germany); Pohl, J.; Weyers, M. [Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Str. 4, Berlin 12489 (Germany)

    2014-10-20

    High brightness photonic band crystal lasers in the passive mode locking regime are presented. Optical pulses with peak power of 3 W and peak brightness of about 180 MW cm{sup −2} sr{sup −1} are obtained on a 5 GHz device exhibiting 15 ps pulses and a very low beam divergence in both the vertical and horizontal directions.

  15. High brightness photonic band crystal semiconductor lasers in the passive mode locking regime

    International Nuclear Information System (INIS)

    Rosales, R.; Kalosha, V. P.; Miah, M. J.; Bimberg, D.; Posilović, K.; Pohl, J.; Weyers, M.

    2014-01-01

    High brightness photonic band crystal lasers in the passive mode locking regime are presented. Optical pulses with peak power of 3 W and peak brightness of about 180 MW cm −2  sr −1 are obtained on a 5 GHz device exhibiting 15 ps pulses and a very low beam divergence in both the vertical and horizontal directions.

  16. Quantum-dot temperature profiles during laser irradiation for semiconductor-doped glasses

    International Nuclear Information System (INIS)

    Nagpal, Swati

    2002-01-01

    Temperature profiles around laser irradiated CdX (X=S, Se, and Te) quantum dots in borosilicate glasses were theoretically modeled. Initially the quantum dots heat up rapidly, followed by a gradual increase of temperature. Also it is found that larger dots reach higher temperatures for the same pulse characteristics. After the pulse is turned off, the dots initially cool rapidly, followed by a gradual decrease in temperature

  17. Quantum-dot temperature profiles during laser irradiation for semiconductor-doped glasses

    Science.gov (United States)

    Nagpal, Swati

    2002-12-01

    Temperature profiles around laser irradiated CdX (X=S, Se, and Te) quantum dots in borosilicate glasses were theoretically modeled. Initially the quantum dots heat up rapidly, followed by a gradual increase of temperature. Also it is found that larger dots reach higher temperatures for the same pulse characteristics. After the pulse is turned off, the dots initially cool rapidly, followed by a gradual decrease in temperature.

  18. Generalized bipolariton model. propagation of a ultrashort laser pulse through a thin semiconductor film in the conditions of two-photon generation of biexcitons

    International Nuclear Information System (INIS)

    Igor Beloussov

    2013-01-01

    A generalized bipolariton model is proposed. Bipolaritons is formed from virtual excitons of four kinds. There exists both attractive and repulsive interaction between these excitons, though only excitons of a specific type can interact with light. A substantial difference between conventional and our models is shown for the case of nonlinear transmission/reflection of ultrashort laser pulses by a thin semiconductor film under two-photon generation of biexcitons. (author)

  19. Semiconductor Optics

    CERN Document Server

    Klingshirn, Claus F

    2012-01-01

    This updated and enlarged new edition of Semiconductor Optics provides an introduction to and an overview of semiconductor optics from the IR through the visible to the UV, including linear and nonlinear optical properties, dynamics, magneto and electrooptics, high-excitation effects and laser processes, some applications, experimental techniques and group theory. The mathematics is kept as elementary as possible, sufficient for an intuitive understanding of the experimental results and techniques treated. The subjects covered extend from physics to materials science and optoelectronics. Significantly updated chapters add coverage of current topics such as electron hole plasma, Bose condensation of excitons and meta materials. Over 120 problems, chapter introductions and a detailed index make it the key textbook for graduate students in physics. The mathematics is kept as elementary as possible, sufficient for an intuitive understanding of the experimental results and techniques treated. The subjects covered ...

  20. Liquid detection with InGaAsP semiconductor lasers having multiple short external cavities.

    Science.gov (United States)

    Zhu, X; Cassidy, D T

    1996-08-20

    A liquid detection system consisting of a diode laser with multiple short external cavities (MSXC's) is reported. The MSXC diode laser operates single mode on one of 18 distinct modes that span a range of 72 nm. We selected the modes by setting the length of one of the external cavities using a piezoelectric positioner. One can measure the transmission through cells by modulating the injection current at audio frequencies and using phase-sensitive detection to reject the ambient light and reduce 1/f noise. A method to determine regions of single-mode operation by the rms of the output of the laser is described. The transmission data were processed by multivariate calibration techniques, i.e., partial least squares and principal component regression. Water concentration in acetone was used to demonstrate the performance of the system. A correlation coefficient of R(2) = 0.997 and 0.29% root-mean-square error of prediction are found for water concentration over the range of 2-19%.

  1. Laser isotope purification of lead for use in semiconductor chip interconnects

    International Nuclear Information System (INIS)

    Scheibner, K.; Haynam, C.; Worden, E.; Esser, B.

    1996-01-01

    Lead, used throughout the electronics industries, typically contains small amounts of radioactive 210 Pb (a daughter product of the planets ubiquitous 238 U) whose 210 Po daughter emits an α-particle that is known to cause soft errors in electronic circuits. The 210 Pb is not separable by chemical means. This paper describes the generic Atomic Vapor Laser Isotope Separation (AVLIS) process developed at the Lawrence Livermore National Laboratory (LLNL) over the last 20 years, with particular emphasis on recent efforts to develop the process physics and component technologies required to remove the offending 210 Pb using lasers. We have constructed a developmental facility that includes a process laser development area and a test bed for the vaporizer and ion and product collectors. We will be testing much of the equipment and demonstrating pilot scale AVLIS on a surrogate material later this year. Detection of the very low alpha emission even from commercially available low-alpha lead is challenging. LLNL's detection capabilities will be described. The goal of the development of lead purification technology is to demonstrate the capability in FY97, and to deploy a production machine capable of up to several MT/y of isotopically purified material, possible beginning in FY98

  2. The danger of semiconductor laser diode radiation to the human eye

    International Nuclear Information System (INIS)

    Nier, J.

    1977-01-01

    The UVV 'Laserstrahlen' (laser beam regulation) sets maximum permissible values for radiation exposure that must not be exceeded on the cornea or skin (wavelength range 200 to 1400nm; cornea values: Normal pulsed operation 5 x 10 -7 Ws/cm 2 , continuous operation (>0.1s)5 x 10 -6 W/cm 2 ). Especially laser diodes emitting in the near infrared invite careless handling, of which this paper warns by a detailed illustration of the danger involved and by numerical examples. Data are given on two commercial laser diodes, a continuous operation diode (continuous power 5mW) and a pulse diode (peak pwer 1W, pulse duration 0.2μs), as well as data on aperture angles and geometrical dimensions. Critical cornea and skin distances are distinguished below which the exposure of cornea and skin in the axis of the emission beam is dangerous. For the unfavourable conditions of focussing with a lens (f = 4cm), the following critical cornea distances are obtained: Continuous diode 2.5 km; pulse diode 23.5m. Calculation formulas for special cases are given. (orig.) 891 MG [de

  3. Use of a reflective semiconductor optical amplifier and dual-ring architecture design to produce a stable multi-wavelength fiber laser

    International Nuclear Information System (INIS)

    Yeh, Chien-Hung; Chow, Chi-Wai; Lu, Shao-Sheng

    2014-01-01

    In this work, we propose and demonstrate a multi-wavelength laser source produced by utilizing a C-band reflective semiconductor optical amplifier (RSOA) with a dual-ring fiber cavity. Here, the laser cavity consists of an RSOA, a 1 × 2 optical coupler, a 2 × 2 optical coupler and a polarization controller. As a result, thirteen to eighteen wavelengths around the L band could be generated simultaneously when the bias current of the C-band RSOA was driven at 30–70 mA. In addition, the output stabilities of the power and wavelength are also discussed. (paper)

  4. Use of a reflective semiconductor optical amplifier and dual-ring architecture design to produce a stable multi-wavelength fiber laser

    Science.gov (United States)

    Yeh, Chien-Hung; Chow, Chi-Wai; Lu, Shao-Sheng

    2014-05-01

    In this work, we propose and demonstrate a multi-wavelength laser source produced by utilizing a C-band reflective semiconductor optical amplifier (RSOA) with a dual-ring fiber cavity. Here, the laser cavity consists of an RSOA, a 1 × 2 optical coupler, a 2 × 2 optical coupler and a polarization controller. As a result, thirteen to eighteen wavelengths around the L band could be generated simultaneously when the bias current of the C-band RSOA was driven at 30-70 mA. In addition, the output stabilities of the power and wavelength are also discussed.

  5. Flight demonstration of flight termination system and solid rocket motor ignition using semiconductor laser initiated ordnance

    Science.gov (United States)

    Schulze, Norman R.; Maxfield, B.; Boucher, C.

    1995-01-01

    Solid State Laser Initiated Ordnance (LIO) offers new technology having potential for enhanced safety, reduced costs, and improved operational efficiency. Concerns over the absence of programmatic applications of the technology, which has prevented acceptance by flight programs, should be abated since LIO has now been operationally implemented by the Laser Initiated Ordnance Sounding Rocket Demonstration (LOSRD) Program. The first launch of solid state laser diode LIO at the NASA Wallops Flight Facility (WFF) occurred on March 15, 1995 with all mission objectives accomplished. This project, Phase 3 of a series of three NASA Headquarters LIO demonstration initiatives, accomplished its objective by the flight of a dedicated, all-LIO sounding rocket mission using a two-stage Nike-Orion launch vehicle. LIO flight hardware, made by The Ensign-Bickford Company under NASA's first Cooperative Agreement with Profit Making Organizations, safely initiated three demanding pyrotechnic sequence events, namely, solid rocket motor ignition from the ground and in flight, and flight termination, i.e., as a Flight Termination System (FTS). A flight LIO system was designed, built, tested, and flown to support the objectives of quickly and inexpensively putting LIO through ground and flight operational paces. The hardware was fully qualified for this mission, including component testing as well as a full-scale system test. The launch accomplished all mission objectives in less than 11 months from proposal receipt. This paper concentrates on accomplishments of the ordnance aspects of the program and on the program's implementation and results. While this program does not generically qualify LIO for all applications, it demonstrated the safety, technical, and operational feasibility of those two most demanding applications, using an all solid state safe and arm system in critical flight applications.

  6. Time delay signature elimination of chaos in a semiconductor laser by dispersive feedback from a chirped FBG.

    Science.gov (United States)

    Wang, Daming; Wang, Longsheng; Zhao, Tong; Gao, Hua; Wang, Yuncai; Chen, Xianfeng; Wang, Anbang

    2017-05-15

    Time delay signature (TDS) of a semiconductor laser subject to dispersive optical feedback from a chirped fibre Bragg grating (CFBG) is investigated experimentally and numerically. Different from mirror, CFBG provides additional frequency-dependent delay caused by dispersion, and thus induces external-cavity modes with irregular mode separation rather than a fixed separation induced by mirror feedback. Compared with mirror feedback, the CFBG feedback can greatly depress and even eliminate the TDS, although it leads to a similar quasi-period route to chaos with increases of feedback. In experiments, by using a CFBG with dispersion of 2000ps/nm, the TDS is decreased by 90% to about 0.04 compared with mirror feedback. Furthermore, both numerical and experimental results show that the TDS evolution is quite different: the TDS decreases more quickly down to a lower plateau (even background noise level of autocorrelation function) and never rises again. This evolution tendency is also different from that of FBG feedback, of which the TDS first decreases to a minimal value and then increases again as feedback strength increases. In addition, the CFBG feedback has no filtering effects and does not require amplification for feedback light.

  7. Development of Prototype Micro-Lidar using Narrow Linewidth Semiconductor Lasers for Mars Boundary Layer Wind and Dust Opacity Profiles

    Science.gov (United States)

    Menzies, Robert T.; Cardell, Greg; Chiao, Meng; Esproles, Carlos; Forouhar, Siamak; Hemmati, Hamid; Tratt, David

    1999-01-01

    We have developed a compact Doppler lidar concept which utilizes recent developments in semiconductor diode laser technology in order to be considered suitable for wind and dust opacity profiling in the Mars lower atmosphere from a surface location. The current understanding of the Mars global climate and meteorology is very limited, with only sparse, near-surface data available from the Viking and Mars Pathfinder landers, supplemented by long-range remote sensing of the Martian atmosphere. The in situ measurements from a lander-based Doppler lidar would provide a unique dataset particularly for the boundary layer. The coupling of the radiative properties of the lower atmosphere with the dynamics involves the radiative absorption and scattering effects of the wind-driven dust. Variability in solar irradiance, on diurnal and seasonal time scales, drives vertical mixing and PBL (planetary boundary layer) thickness. The lidar data will also contribute to an understanding of the impact of wind-driven dust on lander and rover operations and lifetime through an improvement in our understanding of Mars climatology. In this paper we discuss the Mars lidar concept, and the development of a laboratory prototype for performance studies, using, local boundary layer and topographic target measurements.

  8. Photonic microwave carrier recovery using period-one nonlinear dynamics of semiconductor lasers for OFDM-RoF coherent detection.

    Science.gov (United States)

    Hung, Yu-Han; Yan, Jhih-Heng; Feng, Kai-Ming; Hwang, Sheng-Kwang

    2017-06-15

    This study investigates an all-optical scheme based on period-one (P1) nonlinear dynamics of semiconductor lasers, which regenerates the microwave carrier of an orthogonal frequency division multiplexing radio-over-fiber (OFDM-RoF) signal and uses it as a microwave local oscillator for coherent detection. Through the injection locking established between the OFDM-RoF signal and the P1 dynamics, frequency synchronization with highly preserved phase quality is inherently achieved between the recovered microwave carrier and the microwave carrier of the OFDM-RoF signal. A bit-error ratio down to 1.9×10-9 is achieved accordingly using the proposed scheme for coherent detection of a 32-GHz OFDM-RoF signal carrying 4  Gb/s 16-quadrature amplitude modulation data. No electronic microwave generators or electronic phase-locked loops are thus required. The proposed system can be operated up to at least 100 GHz and can be self-adapted to certain changes in the operating microwave frequency.

  9. Short-range remote spectral sensor using mid-infrared semiconductor lasers with orthogonal code-division multiplexing approach

    Science.gov (United States)

    Morbi, Zulfikar; Ho, D. B.; Ren, H.-W.; Le, Han Q.; Pei, Shin Shem

    2002-09-01

    Demonstration of short-range multispectral remote sensing, using 3 to 4-micrometers mid- infrared Sb semiconductor lasers based on code-division multiplexing (CDM) architecture, is described. The system is built on a principle similar to intensity- modulated/direct-detection optical-CDMA for communications, but adapted for sensing with synchronous, orthogonal codes to distinguish different wavelength channels with zero interchannel correlation. The concept is scalable for any number of channels, and experiments with a two-wavelength system are conducted. The CDM-signal processing yielded a white-Gaussian-like system noise that is found to be near the theoretical level limited by the detector fundamental intrinsic noise. With sub-mW transmitter average power, the system was able to detect an open-air acetylene gas leak of 10-2 STP ft3/hr from 10-m away with time-varying, random, noncooperative backscatters. A similar experiment detected and positively distinguished hydrocarbon oil contaminants on water from bio-organic oils and detergents. Projection for more advanced systems suggests a multi-kilometer-range capability for watt-level transmitters, and hundreds of wavelength channels can also be accommodated for active hyperspectral remote sensing application.

  10. Relaxation dynamics of femtosecond-laser-induced temperature modulation on the surfaces of metals and semiconductors

    Czech Academy of Sciences Publication Activity Database

    Levy, Yoann; Derrien, Thibault; Bulgakova, Nadezhda M.; Gurevich, E.L.; Mocek, Tomáš

    2016-01-01

    Roč. 374, Jun (2016), s. 157-164 ISSN 0169-4332 R&D Projects: GA MŠk ED2.1.00/01.0027 Grant - others:HILASE(XE) CZ.1.05/2.1.00/01.0027; OP VK 6(XE) CZ.1.07/2.3.00/20.0143; OP VK 6(XE) CZ.1.07/2.3.00/20.0143 Institutional support: RVO:68378271 Keywords : LIPSS * modulated temperature relaxation * two-temperature model * nano-melting Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.387, year: 2016

  11. International Semiconductor Laser Conference. Held in Boston, Massachusetts on August 29 - September 1, 1988

    Science.gov (United States)

    1988-11-01

    gastronomically rewarding. Excellent restaurants serving seafood, "natural-foods’, and European and Asian dishes are everywhere. A baseball game at nearby...Laboratories, Holmdel, NJ, USA .......... 6-7 A:4 9:00 am DFB Lasers with a Crescent-Shaped Active Layer on a Corrugated p-type Substrate Y Ogawa, H. Horikawa...Berkeley, CA, USA ; W.M. Clark Jr., E.H. Stevens and MW Utlaut, Hughes Research Laboratories, Malibu, CA, USA .. 12-13 A:7 9:45 am Nanosecond Wavelength

  12. Semiconductor detectors for observation of multi-MeV protons and ions produced by lasers

    Czech Academy of Sciences Publication Activity Database

    Krása, Josef; Klir, D.; De Marco, Massimo; Cikhardt, J.; Velyhan, Andriy; Řezáč, Karel; Pfeifer, Miroslav; Krouský, Eduard; Ryć, L.; Dostál, Jan; Kaufman, Jan; Ullschmied, Jiří; Limpouch, J.

    2016-01-01

    Roč. 3, č. 1 (2016), 9-11 ISSN 2336-2626 R&D Projects: GA ČR GA16-07036S; GA MŠk EF15_008/0000162; GA MŠk(CZ) LD14089 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:68378271 ; RVO:61389021 Keywords : laser-accelerated ions * ion collectors * SiC detectors * similarity relations * electromagnetic pulse Subject RIV: BL - Plasma and Gas Discharge Physics

  13. Effect of carrier dynamics and temperature on two-state lasing in semiconductor quantum dot lasers

    Energy Technology Data Exchange (ETDEWEB)

    Korenev, V. V., E-mail: korenev@spbau.ru; Savelyev, A. V.; Zhukov, A. E.; Omelchenko, A. V.; Maximov, M. V. [Saint Petersburg Academic University-Nanotechnology Research and Education Center (Russian Federation)

    2013-10-15

    It is analytically shown that the both the charge carrier dynamics in quantum dots and their capture into the quantum dots from the matrix material have a significant effect on two-state lasing phenomenon in quantum dot lasers. In particular, the consideration of desynchronization in electron and hole capture into quantum dots allows one to describe the quenching of ground-state lasing observed at high injection currents both qualitatevely and quantitatively. At the same time, an analysis of the charge carrier dynamics in a single quantum dot allowed us to describe the temperature dependences of the emission power via the ground- and excited-state optical transitions of quantum dots.

  14. Effect of carrier dynamics and temperature on two-state lasing in semiconductor quantum dot lasers

    International Nuclear Information System (INIS)

    Korenev, V. V.; Savelyev, A. V.; Zhukov, A. E.; Omelchenko, A. V.; Maximov, M. V.

    2013-01-01

    It is analytically shown that the both the charge carrier dynamics in quantum dots and their capture into the quantum dots from the matrix material have a significant effect on two-state lasing phenomenon in quantum dot lasers. In particular, the consideration of desynchronization in electron and hole capture into quantum dots allows one to describe the quenching of ground-state lasing observed at high injection currents both qualitatevely and quantitatively. At the same time, an analysis of the charge carrier dynamics in a single quantum dot allowed us to describe the temperature dependences of the emission power via the ground- and excited-state optical transitions of quantum dots

  15. Doping Optimization for High Efficiency in Semiconductor Diode Lasers and Amplifiers

    Science.gov (United States)

    2016-03-01

    ηiVph αm αm + αi (I − Ith) , (12) where ηi is the internal quantum efficiency, Vph is the voltage associated with the energy of a single photon, and...efficiency. In general, this could be a negligible detail; however, for certain cases such as V0 Vph , the difference could be significant, since...communications applications. Bour and Rosen provided an expression for the maximum PCE of a diode laser, given as [12] ηPCE = ηi Vph V0 αm αm + αi x( 1 + √ 1 + x

  16. Laser ablation and deposition of wide bandgap semiconductors: plasma and nanostructure of deposits diagnosis

    Science.gov (United States)

    Sanz, M.; López-Arias, M.; Rebollar, E.; de Nalda, R.; Castillejo, M.

    2011-12-01

    Nanostructured CdS and ZnS films on Si (100) substrates were obtained by nanosecond pulsed laser deposition at the wavelengths of 266 and 532 nm. The effect of laser irradiation wavelength on the surface structure and crystallinity of deposits was characterized, together with the composition, expansion dynamics and thermodynamic parameters of the ablation plume. Deposits were analyzed by environmental scanning electron microscopy, atomic force microscopy and X-ray diffraction, while in situ monitoring of the plume was carried out with spectral, temporal and spatial resolution by optical emission spectroscopy. The deposits consist of 25-50 nm nanoparticle assembled films but ablation in the visible results in larger aggregates (150 nm) over imposed on the film surface. The aggregate free films grown at 266 nm on heated substrates are thicker than those grown at room temperature and in the former case they reveal a crystalline structure congruent with that of the initial target material. The observed trends are discussed in reference to the light absorption step, the plasma composition and the nucleation processes occurring on the substrate.

  17. Semiconductor lasers driven by self-sustained chaotic electronic oscillators and applications to optical chaos cryptography.

    Science.gov (United States)

    Kingni, Sifeu Takougang; Mbé, Jimmi Hervé Talla; Woafo, Paul

    2012-09-01

    In this work, we numerically study the dynamics of vertical cavity surface emitting laser (VCSEL) firstly when it is driven by Chua's oscillator, secondly in case where it is driven by a broad frequency spectral bandwidth chaotic oscillator developed by Nana et al. [Commun. Nonlinear Sci. Numer. Simul. 14, 2266 (2009)]. We demonstrated that the VCSEL generated robust chaotic dynamics compared to the ones found in VCSEL subject to a sinusoidally modulated current and therefore it is more suitable for chaos encryption techniques. The synchronization characteristics and the communication performances of unidirectional coupled VCSEL driven by the broad frequency spectral bandwidth chaotic oscillators are investigated numerically. The results show that high-quality synchronization and transmission of messages can be realized for suitable system parameters. Chaos shift keying method is successfully applied to encrypt a message at a high bitrate.

  18. Bubbling and bistability in two parameter discrete systems

    Indian Academy of Sciences (India)

    The birth of X *. · is concurrent with the ... for bistability viz. a½, and the higher order bistability points a¾, etc. are marked. The quadrilateral marked as ... The characteristics of 2 parameter 1-d maps that exhibit bubbling/bistability related to their ...

  19. Photobiostimulation effects on germination and early growth of wheat seeds (Triticum aestivum L) produced by a semiconductor laser with λ=980nm

    International Nuclear Information System (INIS)

    Michtchenko, A.; Hernandez, M.

    2009-01-01

    The effect of the exposure of wheat (Triticum aestivum L) seeds to a IR laser radiation with λ=980nm produced by a semiconductor laser on germination and early growth had been studied under laboratory conditions. Seeds were irradiated to one of two laser intensities 15 mWcm - ''2 or 30 mWcm -2 for different periods of time 30, 60 or 120 s. Seeds exposed to a light intensity of 15mWcm -2 and an exposition time of 30 s. showed an increase on the percentage of seeds germinated normally while the percentage of seeds germinated abnormally decreased. At the same time there is a stimulation effect on the growth of the stem and on the growth of the root of 10% on wheat seedlings over control seedlings. Significant differences (ρ < 0.001) were observed between the control and the above treatment. (Author)

  20. Vortex Laser based on III-V semiconductor metasurface: direct generation of coherent Laguerre-Gauss modes carrying controlled orbital angular momentum.

    Science.gov (United States)

    Seghilani, Mohamed S; Myara, Mikhael; Sellahi, Mohamed; Legratiet, Luc; Sagnes, Isabelle; Beaudoin, Grégoire; Lalanne, Philippe; Garnache, Arnaud

    2016-12-05

    The generation of a coherent state, supporting a large photon number, with controlled orbital-angular-momentum L = ħl (of charge l per photon) presents both fundamental and technological challenges: we demonstrate a surface-emitting laser, based on III-V semiconductor technology with an integrated metasurface, generating vortex-like coherent state in the Laguerre-Gauss basis. We use a first order phase perturbation to lift orbital degeneracy of wavefunctions, by introducing a weak anisotropy called here "orbital birefringence", based on a dielectric metasurface. The azimuthal symmetry breakdown and non-linear laser dynamics create "orbital gain dichroism" allowing selecting vortex handedness. This coherent photonic device was characterized and studied, experimentally and theoretically. It exhibits a low divergence (50 dB vortex purity), and single frequency operation in a stable low noise regime (0.1% rms). Such high performance laser opens the path to widespread new photonic applications.

  1. Perceptual incongruence influences bistability and cortical activation.

    Directory of Open Access Journals (Sweden)

    Gijs Joost Brouwer

    Full Text Available We employed a parametric psychophysical design in combination with functional imaging to examine the influence of metric changes in perceptual incongruence on perceptual alternation rates and cortical responses. Subjects viewed a bistable stimulus defined by incongruent depth cues; bistability resulted from incongruence between binocular disparity and monocular perspective cues that specify different slants (slant rivalry. Psychophysical results revealed that perceptual alternation rates were positively correlated with the degree of perceived incongruence. Functional imaging revealed systematic increases in activity that paralleled the psychophysical results within anterior intraparietal sulcus, prior to the onset of perceptual alternations. We suggest that this cortical activity predicts the frequency of subsequent alternations, implying a putative causal role for these areas in initiating bistable perception. In contrast, areas implicated in form and depth processing (LOC and V3A were sensitive to the degree of slant, but failed to show increases in activity when these cues were in conflict.

  2. Longitudinal magnetic bistability of electroplated wires

    International Nuclear Information System (INIS)

    Kurlyandskaya, G.V.; Garcia-Miquel, H.; Vazquez, M.; Svalov, A.V.; Vas'kovskiy, V.O.

    2002-01-01

    Fe 20 Ni 74 Co 6 and Fe 20 Ni 64 Co 16 1 μm thick magnetic tubes electroplated onto Cu 98 Be 2 conductive wire have been investigated in as-deposited state, after heat treatment under longitudinal magnetic field for 1 h at 330 deg. C, and after rf-sputtering deposition of the additional 2 μm Fe 19 Ni 81 layer. Heat treatments and an additional layer deposition modify the shape of hysteresis loops. Magnetically bistable behaviour, observed after the field annealing at a temperature of 330 deg. C, is studied as a function of the length of the samples. This is the first report by our knowledge on the bistable behaviour of the electroplated wires. The bistability of these wires is promising for applications such as tagging or pulse generator applications

  3. Balancing bistable perception during self-motion.

    Science.gov (United States)

    van Elk, Michiel; Blanke, Olaf

    2012-10-01

    In two experiments we investigated whether bistable visual perception is influenced by passive own body displacements due to vestibular stimulation. For this we passively rotated our participants around the vertical (yaw) axis while observing different rotating bistable stimuli (bodily or non-bodily) with different ambiguous motion directions. Based on previous work on multimodal effects on bistable perception, we hypothesized that vestibular stimulation should alter bistable perception and that the effects should differ for bodily versus non-bodily stimuli. In the first experiment, it was found that the rotation bias (i.e., the difference between the percentage of time that a CW or CCW rotation was perceived) was selectively modulated by vestibular stimulation: the perceived duration of the bodily stimuli was longer for the rotation direction congruent with the subject's own body rotation, whereas the opposite was true for the non-bodily stimulus (Necker cube). The results found in the second experiment extend the findings from the first experiment and show that these vestibular effects on bistable perception only occur when the axis of rotation of the bodily stimulus matches the axis of passive own body rotation. These findings indicate that the effect of vestibular stimulation on the rotation bias depends on the stimulus that is presented and the rotation axis of the stimulus. Although most studies on vestibular processing have traditionally focused on multisensory signal integration for posture, balance, and heading direction, the present data show that vestibular self-motion influences the perception of bistable bodily stimuli revealing the importance of vestibular mechanisms for visual consciousness.

  4. Laser-induced removal of a dye C.I. Acid Red 87 using n-type WO{sub 3} semiconductor catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Qamar, M. [Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, KFUPM Box 741, Dhahran 31261 (Saudi Arabia); Gondal, M.A., E-mail: magondal@kfupm.edu.sa [Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, KFUPM Box 741, Dhahran 31261 (Saudi Arabia); Laser Research Laboratory, Physics Department, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Hayat, K. [Chemistry Department, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Yamani, Z.H. [Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, KFUPM Box 741, Dhahran 31261 (Saudi Arabia); Laser Research Laboratory, Physics Department, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia); Al-Hooshani, K. [Center of Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, KFUPM Box 741, Dhahran 31261 (Saudi Arabia); Chemistry Department, King Fahd University of Petroleum and Minerals, Dhahran 31261 (Saudi Arabia)

    2009-10-30

    Water contamination by organic substances such as dyes is of great concern worldwide due to their utilization in many industrial processes and environmental concerns. To cater the needs for waste water treatment polluted with organic dyes, laser-induced photocatalytic process was investigated for removal of a dye derivative namely Acid Red 87 using n-type WO{sub 3} semiconductor catalyst. The degradation was investigated in aqueous suspensions of tungsten oxide under different experimental conditions using laser instead of conventional UV lamp as an irradiation source. The degradation process was monitored by measuring the change in dye concentration as a function of laser irradiation time by employing UV spectroscopic analysis. The degradation of dye was studied by varying different parameters such as laser energy, reaction pH, substrate concentration, catalyst concentration, and in the presence of electron acceptors such as hydrogen peroxide (H{sub 2}O{sub 2}), and potassium bromate (KBrO{sub 3}). The degradation rates were found to be strongly dependent on all the above-mentioned parameters. Our experimental results revealed that the dye degradation process was very fast (within few minutes) under laser irradiation as compared to conventional setups using broad spectral lamps (hours or days) and this laser-induced photocatalytic degradation method could be an effective means to eliminate the pollutants present in liquid phase. The experience gained through this study could be beneficial for treatment of waste water contaminated with organic dyes and other organic pollutants.

  5. Bistable Microvalve For Use With Microcatheter System

    Science.gov (United States)

    Seward, Kirk Patrick

    2003-12-16

    A bistable microvalve of shape memory material is operatively connected to a microcatheter. The bistable microvalve includes a tip that can be closed off until it is in the desired position. Once it is in position it can be opened and closed. The system uses heat and pressure to open and close the microvalve. The shape memory material will change stiffness and shape when heated above a transition temperature. The shape memory material is adapted to move from a first shape to a second shape, either open or closed, where it can perform a desired function.

  6. Unidirectional Transition Waves in Bistable Lattices.

    Science.gov (United States)

    Nadkarni, Neel; Arrieta, Andres F; Chong, Christopher; Kochmann, Dennis M; Daraio, Chiara

    2016-06-17

    We present a model system for strongly nonlinear transition waves generated in a periodic lattice of bistable members connected by magnetic links. The asymmetry of the on-site energy wells created by the bistable members produces a mechanical diode that supports only unidirectional transition wave propagation with constant wave velocity. We theoretically justify the cause of the unidirectionality of the transition wave and confirm these predictions by experiments and simulations. We further identify how the wave velocity and profile are uniquely linked to the double-well energy landscape, which serves as a blueprint for transition wave control.

  7. Bistable Topological Insulator with Exciton-Polaritons

    Science.gov (United States)

    Kartashov, Yaroslav V.; Skryabin, Dmitry V.

    2017-12-01

    The functionality of many nonlinear and quantum optical devices relies on the effect of optical bistability. Using microcavity exciton-polaritons in a honeycomb arrangement of microcavity pillars, we report the resonance response and bistability of topological edge states. A balance between the pump, loss, and nonlinearity ensures a broad range of dynamical stability and controls the distribution of power between counterpropagating states on the opposite edges of the honeycomb lattice stripe. Tuning energy and polarization of the pump photons, while keeping their momentum constant, we demonstrate control of the propagation direction of the dominant edge state. Our results facilitate the development of practical applications of topological photonics.

  8. Bistable firing properties of soleus motor units in unrestrained rats

    DEFF Research Database (Denmark)

    EKEN, T.; KIEHN, O.

    1989-01-01

    of the motoneuron pool by stimulation of la afferents, or inhibition by stimulation of skin afferents. The shifts were not related to gross limb movements. This phenomenon is referred to as a bistable firing pattern. Bistable firing also occurred spontaneously during quiet standing. Typically the firing frequency...... was unchanged or only phasically influenced. These results demonstrate for the first time a bistable firing pattern during postural activity in the intact animal. The firing pattern closely resembles the bistable behaviour described in spinal motoneurons in reduced preparations, where it is due to the presence...... of a plateau potential. This suggests that the bistable firing is unexplained by plateau potentials also in the intact animal....

  9. Neuromechanistic Model of Auditory Bistability.

    Directory of Open Access Journals (Sweden)

    James Rankin

    2015-11-01

    Full Text Available Sequences of higher frequency A and lower frequency B tones repeating in an ABA- triplet pattern are widely used to study auditory streaming. One may experience either an integrated percept, a single ABA-ABA- stream, or a segregated percept, separate but simultaneous streams A-A-A-A- and -B---B--. During minutes-long presentations, subjects may report irregular alternations between these interpretations. We combine neuromechanistic modeling and psychoacoustic experiments to study these persistent alternations and to characterize the effects of manipulating stimulus parameters. Unlike many phenomenological models with abstract, percept-specific competition and fixed inputs, our network model comprises neuronal units with sensory feature dependent inputs that mimic the pulsatile-like A1 responses to tones in the ABA- triplets. It embodies a neuronal computation for percept competition thought to occur beyond primary auditory cortex (A1. Mutual inhibition, adaptation and noise are implemented. We include slow NDMA recurrent excitation for local temporal memory that enables linkage across sound gaps from one triplet to the next. Percepts in our model are identified in the firing patterns of the neuronal units. We predict with the model that manipulations of the frequency difference between tones A and B should affect the dominance durations of the stronger percept, the one dominant a larger fraction of time, more than those of the weaker percept-a property that has been previously established and generalized across several visual bistable paradigms. We confirm the qualitative prediction with our psychoacoustic experiments and use the behavioral data to further constrain and improve the model, achieving quantitative agreement between experimental and modeling results. Our work and model provide a platform that can be extended to consider other stimulus conditions, including the effects of context and volition.

  10. Controllable optical bistability and multistability in a graphene monolayer system

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Duo, E-mail: zhangduo10@126.com [School of Electrical and Electronic Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Sun, Zhaoyu [School of Electrical and Electronic Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Ding, Chunling [School of Physics and Electronics, Henan University, Kaifeng 475004 (China); Yu, Rong [School of Science, Hubei Province Key Laboratory of Intelligent Robot, Wuhan Institute of Technology, Wuhan 430073 (China); Yang, Xiaoxue [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2016-02-15

    We theoretically investigate the behavior of optical bistability (OB) and optical multistability (OM) in a graphene monolayer system driven by an elliptically polarized control field and a right-hand circularly polarized probe field. Our numerical results show that it is easy to realize the transition from OB to OM or vice versa by adjusting the frequency detunings of the probe field and the control field, as well as the polarization-dependent phase difference between the two components of the control laser field. The influences of the intensity of the control field and the cooperation parameter on the OB behavior are also discussed in detail. These results may provide some new possibilities for technological applications in optoelectronics and solid-state quantum information science.

  11. Fiber transmission and generation of ultrawideband pulses by direct current modulation of semi-conductor lasers and chirp-to-intensity conversion

    DEFF Research Database (Denmark)

    Company Torres, Victor; Prince, Kamau; Tafur Monroy, Idelfonso

    2008-01-01

    Optical pulses generated by current modulation of semiconductor lasers are strongly frequency chirped. This effect has been considered pernicious for optical communications. We take advantage of this effect for the generation of ultrawideband microwave signals by using an optical filter to achieve...... chirp-to-intensity conversion. We also experimentally achieve propagation through a 20 km nonzero dispersion shifted fiber with no degradation of the signal at the receiver. Our method constitutes a prospective low-cost solution and offers integration capabilities with fiber...

  12. Metastable and bistable defects in silicon

    International Nuclear Information System (INIS)

    Mukashev, Bulat N; Abdullin, Kh A; Gorelkinskii, Yurii V

    2000-01-01

    Existing data on the properties and structure of metastable and bistable defects in silicon are analyzed. Primary radiation-induced defects (vacancies, self-interstitial atoms, and Frenkel pairs), complexes of oxygen, carbon, hydrogen, and other impurity atoms and defects with negative correlation energy are considered. (reviews of topical problems)

  13. Organic bistable light-emitting devices

    Science.gov (United States)

    Ma, Liping; Liu, Jie; Pyo, Seungmoon; Yang, Yang

    2002-01-01

    An organic bistable device, with a unique trilayer structure consisting of organic/metal/organic sandwiched between two outmost metal electrodes, has been invented. [Y. Yang, L. P. Ma, and J. Liu, U.S. Patent Pending, U.S. 01/17206 (2001)]. When the device is biased with voltages beyond a critical value (for example 3 V), the device suddenly switches from a high-impedance state to a low-impedance state, with a difference in injection current of more than 6 orders of magnitude. When the device is switched to the low-impedance state, it remains in that state even when the power is off. (This is called "nonvolatile" phenomenon in memory devices.) The high-impedance state can be recovered by applying a reverse bias; therefore, this bistable device is ideal for memory applications. In order to increase the data read-out rate of this type of memory device, a regular polymer light-emitting diode has been integrated with the organic bistable device, such that it can be read out optically. These features make the organic bistable light-emitting device a promising candidate for several applications, such as digital memories, opto-electronic books, and recordable papers.

  14. A CW Gunn diode bistable switching element.

    Science.gov (United States)

    Hurtado, M.; Rosenbaum, F. J.

    1972-01-01

    Experiments with a current-controlled bistable switching element using a CW Gunn diode are reported. Switching rates of the order of 10 MHz have been obtained. Switching is initiated by current pulses of short duration (5-10 ns). Rise times of the order of several nanoseconds could be obtained.

  15. A bistable model of cell polarity.

    Directory of Open Access Journals (Sweden)

    Matteo Semplice

    Full Text Available Ultrasensitivity, as described by Goldbeter and Koshland, has been considered for a long time as a way to realize bistable switches in biological systems. It is not as well recognized that when ultrasensitivity and reinforcing feedback loops are present in a spatially distributed system such as the cell plasmamembrane, they may induce bistability and spatial separation of the system into distinct signaling phases. Here we suggest that bistability of ultrasensitive signaling pathways in a diffusive environment provides a basic mechanism to realize cell membrane polarity. Cell membrane polarization is a fundamental process implicated in several basic biological phenomena, such as differentiation, proliferation, migration and morphogenesis of unicellular and multicellular organisms. We describe a simple, solvable model of cell membrane polarization based on the coupling of membrane diffusion with bistable enzymatic dynamics. The model can reproduce a broad range of symmetry-breaking events, such as those observed in eukaryotic directional sensing, the apico-basal polarization of epithelium cells, the polarization of budding and mating yeast, and the formation of Ras nanoclusters in several cell types.

  16. Microscopic analysis of the optoelectronic properties of semiconductor gain media for laser applications; Mikroskopische Analyse optoelektronischer Eigenschaften von Halbleiterverstaerkungsmedien fuer Laseranwendungen

    Energy Technology Data Exchange (ETDEWEB)

    Bueckers, Christina

    2010-12-03

    A microscopic many-particle theory is applied to model a wide range of semiconductor laser gain materials. The fundamental understanding of the gain medium and the underlying carrier interaction processes allow for the quantitative prediction of the optoelectronic properties governing the laser performance. Detailed theory-experiment-comparisons are shown for a variety of structures demonstrating the application capabilities of the theoretical approach. The microscopically calculated material properties, in particular absorption, optical gain, luminescence and the intrinsic carrier losses due to radiative and Auger-recombination, constitute the critical input to analyse and design laser structures. On this basis, important system features such as laser wavelength or threshold behaviour become predictable. However, the theory is also used in a diagnostic fashion, e.g. to extract otherwise poorly known structural parameter. Thus, novel concepts for the optimisation of laser designs may be developed with regard to the requirements of specific applications. Moreover, the approach allows for the systematic exploration and assessment of completely novel material systems and their application potential. (orig.)

  17. Triggered Snap-Through of Bistable Shells

    Science.gov (United States)

    Cai, Yijie; Huang, Shicheng; Trase, Ian; Hu, Nan; Chen, Zi

    Elastic bistable shells are common structures in nature and engineering, such as the lobes of the Venus flytrap or the surface of a toy jumping poppers. Despite their ubiquity, the parameters that control the bistability of such structures are not well understood. In this study, we explore how the geometrical features of radially symmetric elastic shells affect the shape and potential energy of a shell's stable states, and how to tune certain parameters in order to generate a snap-through transition from a convex semi-stable state to concave stable state. We fabricated a series of elastic shells with varying geometric parameters out of silicone rubber and measured the resulting potential energy in the semi-stable state. Finite element simulations were also conducted in order to determine the deformation and stress in the shells during snap-through. It was found that the energy of the semi-stable state is controlled by only two geometric parameters and a dimensionless ratio. We also noted two distinct transitions during snap-through, one between monostability and semi-bistability (the state a popper toy is in before it snaps-through and jumps), and a second transition between semi-bistability and true bistability. This work shows that it is possible to use a set of simple parameters to tailor the energy landscape of an elastic shell in order to generate complex trigger motions for their potential use in smart applications. Z.C. acknowledge support from Society in Science-Branco Weiss Fellowship, administered by ETH Zurich.

  18. Review of inductively coupled plasmas: Nano-applications and bistable hysteresis physics

    Science.gov (United States)

    Lee, Hyo-Chang

    2018-03-01

    Many different gas discharges and plasmas exhibit bistable states under a given set of conditions, and the history-dependent hysteresis that is manifested by intensive quantities of the system upon variation of an external parameter has been observed in inductively coupled plasmas (ICPs). When the external parameters (such as discharge powers) increase, the plasma density increases suddenly from a low- to high-density mode, whereas decreasing the power maintains the plasma in a relatively high-density mode, resulting in significant hysteresis. To date, a comprehensive description of plasma hysteresis and a physical understanding of the main mechanism underlying their bistability remain elusive, despite many experimental observations of plasma bistability conducted under radio-frequency ICP excitation. This fundamental understanding of mode transitions and hysteresis is essential and highly important in various applied fields owing to the widespread use of ICPs, such as semiconductor/display/solar-cell processing (etching, deposition, and ashing), wireless light lamp, nanostructure fabrication, nuclear-fusion operation, spacecraft propulsion, gas reformation, and the removal of hazardous gases and materials. If, in such applications, plasma undergoes a mode transition and hysteresis occurs in response to external perturbations, the process result will be strongly affected. Due to these reasons, this paper comprehensively reviews both the current knowledge in the context of the various applied fields and the global understanding of the bistability and hysteresis physics in the ICPs. At first, the basic understanding of the ICP is given. After that, applications of ICPs to various applied fields of nano/environmental/energy-science are introduced. Finally, the mode transition and hysteresis in ICPs are studied in detail. This study will show the fundamental understanding of hysteresis physics in plasmas and give open possibilities for applications to various applied

  19. Mode locking of an external cavity asymmetric quantum-well GaAs/AlGaAs semiconductor laser

    International Nuclear Information System (INIS)

    Vasil'ev, Petr P; Kan, H; Ohta, H; Hiruma, T; Tanaka, K A

    2006-01-01

    A theoretical model of the optical gain in asymmetric GaAs/AlGaAs quantum-well lasers is developed. It is demonstrated that the emission spectrum of asymmetric GaAs/AlGaAs quantum-well lasers is much broader than that of standard quantum-well lasers. The experimental samples of such lasers and superluminescent diodes with the emission bandwidth exceeding 50 nm are fabricated. Wavelength tunable ultrashort pulses with duration of 1-2 ps at repetition rates of 0.4-1 GHz are obtained by active mode locking of an external cavity laser. (lasers)

  20. Passively Q-switched dual-wavelength thulium-doped fiber laser based on a multimode interference filter and a semiconductor saturable absorber

    Science.gov (United States)

    Wang, M.; Huang, Y. J.; Ruan, S. C.

    2018-04-01

    In this paper, we have demonstrated a theta cavity passively Q-switched dual-wavelength fiber laser based on a multimode interference filter and a semiconductor saturable absorber. Relying on the properties of the fiber theta cavity, the laser can operate unidirectionally without an optical isolator. A semiconductor saturable absorber played the role of passive Q-switch while a section of single-mode-multimode-single-mode fiber structure served as an multimode interference filter and was used for selecting the lasing wavelengths. By suitably manipulating the polarization controller, stable dual-wavelength Q-switched operation was obtained at ~1946.8 nm and ~1983.8 nm with maximum output power and minimum pulse duration of ~47 mW and ~762.5 ns, respectively. The pulse repetition rate can be tuned from ~20.2 kHz to ~79.7 kHz by increasing the pump power from ~2.12 W to ~5.4 W.

  1. Bistable scattering in graphene-coated dielectric nanowires.

    Science.gov (United States)

    Li, Rujiang; Wang, Huaping; Zheng, Bin; Dehdashti, Shahram; Li, Erping; Chen, Hongsheng

    2017-06-22

    In nonlinear plasmonics, the switching threshold of optical bistability is limited by the weak nonlinear responses from the conventional Kerr dielectric media. Considering the giant nonlinear susceptibility of graphene, here we develop a nonlinear scattering model under the mean field approximation and study the bistable scattering in graphene-coated dielectric nanowires based on the semi-analytical solutions. We find that the switching intensities of bistable scattering can be smaller than 1 MW cm -2 at the working frequency. To further decrease the switching intensities, we show that the most important factor that restricts the bistable scattering is the relaxation time of graphene. Our work not only reveals some general characteristics of graphene-based bistable scattering, but also provides a guidance to further applications of optical bistability in the high speed all-optical signal processing.

  2. Bistable perception modeled as competing stochastic integrations at two levels.

    Science.gov (United States)

    Gigante, Guido; Mattia, Maurizio; Braun, Jochen; Del Giudice, Paolo

    2009-07-01

    We propose a novel explanation for bistable perception, namely, the collective dynamics of multiple neural populations that are individually meta-stable. Distributed representations of sensory input and of perceptual state build gradually through noise-driven transitions in these populations, until the competition between alternative representations is resolved by a threshold mechanism. The perpetual repetition of this collective race to threshold renders perception bistable. This collective dynamics - which is largely uncoupled from the time-scales that govern individual populations or neurons - explains many hitherto puzzling observations about bistable perception: the wide range of mean alternation rates exhibited by bistable phenomena, the consistent variability of successive dominance periods, and the stabilizing effect of past perceptual states. It also predicts a number of previously unsuspected relationships between observable quantities characterizing bistable perception. We conclude that bistable perception reflects the collective nature of neural decision making rather than properties of individual populations or neurons.

  3. Optical bistability and multistability in polaritonic materials doped with nanoparticles

    International Nuclear Information System (INIS)

    Wang, Zhiping; Yu, Benli

    2014-01-01

    We investigate the optical bistability and multistability in polaritonic materials doped with nanoparticles inside an optical ring cavity. It is found that the optical bistability and multistability can be easily controlled by adjusting the corresponding parameters of the system properly. The effect of the dipole–dipole interaction has also been included in the formulation, which leads to interesting phenomena. Our scheme opens up the possibility of controling the optical bistability and multistability in polaritonic materials doped with nanoparticles. (letter)

  4. Durable bistable auxetics made of rigid solids

    Science.gov (United States)

    Shang, Xiao; Liu, Lu; Rafsanjani, Ahmad; Pasini, Damiano

    2018-02-01

    Bistable Auxetic Metamaterials (BAMs) are a class of monolithic perforated periodic structures with negative Poisson's ratio. Under tension, a BAM can expand and reach a second state of equilibrium through a globally large shape transformation that is ensured by the flexibility of its elastomeric base material. However, if made from a rigid polymer, or metal, BAM ceases to function due to the inevitable rupture of its ligaments. The goal of this work is to extend the unique functionality of the original kirigami architecture of BAM to a rigid solid base material. We use experiments and numerical simulations to assess performance, bistability and durability of rigid BAMs at 10,000 cycles. Geometric maps are presented to elucidate the role of the main descriptors of BAM architecture. The proposed design enables the realization of BAM from a large palette of materials, including elastic-perfectly plastic materials and potentially brittle materials.

  5. Two Bistable Switches Govern M Phase Entry.

    Science.gov (United States)

    Mochida, Satoru; Rata, Scott; Hino, Hirotsugu; Nagai, Takeharu; Novák, Béla

    2016-12-19

    The abrupt and irreversible transition from interphase to M phase is essential to separate DNA replication from chromosome segregation. This transition requires the switch-like phosphorylation of hundreds of proteins by the cyclin-dependent kinase 1 (Cdk1):cyclin B (CycB) complex. Previous studies have ascribed these switch-like phosphorylations to the auto-activation of Cdk1:CycB through the removal of inhibitory phosphorylations on Cdk1-Tyr15 [1, 2]. The positive feedback in Cdk1 activation creates a bistable switch that makes mitotic commitment irreversible [2-4]. Here, we surprisingly find that Cdk1 auto-activation is dispensable for irreversible, switch-like mitotic entry due to a second mechanism, whereby Cdk1:CycB inhibits its counteracting phosphatase (PP2A:B55). We show that the PP2A:B55-inhibiting Greatwall (Gwl)-endosulfine (ENSA) pathway is both necessary and sufficient for switch-like phosphorylations of mitotic substrates. Using purified components of the Gwl-ENSA pathway in a reconstituted system, we found a sharp Cdk1 threshold for phosphorylation of a luminescent mitotic substrate. The Cdk1 threshold to induce mitotic phosphorylation is distinctly higher than the Cdk1 threshold required to maintain these phosphorylations-evidence for bistability. A combination of mathematical modeling and biochemical reconstitution show that the bistable behavior of the Gwl-ENSA pathway emerges from its mutual antagonism with PP2A:B55. Our results demonstrate that two interlinked bistable mechanisms provide a robust solution for irreversible and switch-like mitotic entry. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Bistable (latching) solenoid actuated propellant isolation valve

    Science.gov (United States)

    Wichmann, H.; Deboi, H. H.

    1979-01-01

    The design, fabrication, assembly and test of a development configuration bistable (latching) solenoid actuated propellant isolation valve suitable for the control hydrazine and liquid fluorine to an 800 pound thrust rocket engine is described. The valve features a balanced poppet, utilizing metal bellows, a hard poppet/seat interface and a flexure support system for the internal moving components. This support system eliminates sliding surfaces, thereby rendering the valve free of self generated particles.

  7. Wake fields in semiconductor plasmas

    International Nuclear Information System (INIS)

    Berezhiani, V.I.; Mahajan, S.M.

    1994-05-01

    It is shown that an intense short laser pulse propagating through a semiconductor plasma will generated longitudinal Langmuir waves in its wake. The measurable wake field can be used as a diagnostic to study nonlinear optical phenomena. For narrow gap semiconductors (for examples InSb) with Kane-type dispersion relation, the system can simulate, at currently available laser powers, the physics underlying wake-field accelerators. (author). 9 refs, 1 fig

  8. Interlinked bistable mechanisms generate robust mitotic transitions.

    Science.gov (United States)

    Hutter, Lukas H; Rata, Scott; Hochegger, Helfrid; Novák, Béla

    2017-10-18

    The transitions between phases of the cell cycle have evolved to be robust and switch-like, which ensures temporal separation of DNA replication, sister chromatid separation, and cell division. Mathematical models describing the biochemical interaction networks of cell cycle regulators attribute these properties to underlying bistable switches, which inherently generate robust, switch-like, and irreversible transitions between states. We have recently presented new mathematical models for two control systems that regulate crucial transitions in the cell cycle: mitotic entry and exit, 1 and the mitotic checkpoint. 2 Each of the two control systems is characterized by two interlinked bistable switches. In the case of mitotic checkpoint control, these switches are mutually activating, whereas in the case of the mitotic entry/exit network, the switches are mutually inhibiting. In this Perspective we describe the qualitative features of these regulatory motifs and show that having two interlinked bistable mechanisms further enhances robustness and irreversibility. We speculate that these network motifs also underlie other cell cycle transitions and cellular transitions between distinct biochemical states.

  9. Dynamics of unidirectionally coupled bistable Henon maps

    International Nuclear Information System (INIS)

    Sausedo-Solorio, J.M.; Pisarchik, A.N.

    2011-01-01

    We study dynamics of two bistable Henon maps coupled in a master-slave configuration. In the case of coexistence of two periodic orbits, the slave map evolves into the master map state after transients, which duration determines synchronization time and obeys a -1/2 power law with respect to the coupling strength. This scaling law is almost independent of the map parameter. In the case of coexistence of chaotic and periodic attractors, very complex dynamics is observed, including the emergence of new attractors as the coupling strength is increased. The attractor of the master map always exists in the slave map independently of the coupling strength. For a high coupling strength, complete synchronization can be achieved only for the attractor similar to that of the master map. -- Highlights: → We study dynamics of two bistable Henon maps coupled in a master-slave configuration. → Synchronization time for periodic orbits obeys a -1/2 power law with respect to coupling. → For a high coupling strength, the slave map remains bistable. → Complete synchronization can be achieved only when both maps stay at the same attractor.

  10. Low-frequency fluctuation regime in a multimode semiconductor laser subject to a mode-selective optical feedback

    International Nuclear Information System (INIS)

    Rogister, F.; Sciamanna, M.; Deparis, O.; Megret, P.; Blondel, M.

    2002-01-01

    We study numerically the dynamics of a multimode laser diode subject to a mode-selective optical feedback by using a generalization of the Lang-Kobayashi equations. In this configuration, only one longitudinal mode of the laser is reinjected into the laser cavity; the other modes are free. When the laser operates in the low-frequency fluctuation regime, our model predicts intensity bursts in the free modes simultaneously with dropouts in the selected mode, in good agreement with recent experiments. In the frame of our model, intensity bursts and dropouts are associated with collisions of the system trajectory in phase space with saddle-type antimodes

  11. All-optical logic gates and wavelength conversion via the injection locking of a Fabry-Perot semiconductor laser

    Science.gov (United States)

    Harvey, E.; Pochet, M.; Schmidt, J.; Locke, T.; Naderi, N.; Usechak, N. G.

    2013-03-01

    This work investigates the implementation of all-optical logic gates based on optical injection locking (OIL). All-optical inverting, NOR, and NAND gates are experimentally demonstrated using two distributed feedback (DFB) lasers, a multi-mode Fabry-Perot laser diode, and an optical band-pass filter. The DFB lasers are externally modulated to represent logic inputs into the cavity of the multi-mode Fabry-Perot slave laser. The input DFB (master) lasers' wavelengths are aligned with the longitudinal modes of the Fabry-Perot slave laser and their optical power is used to modulate the injection conditions in the Fabry-Perot slave laser. The optical band-pass filter is used to select a Fabry- Perot mode that is either suppressed or transmitted given the logic state of the injecting master laser signals. When the input signal(s) is (are) in the on state, injection locking, and thus the suppression of the non-injected Fabry-Perot modes, is induced, yielding a dynamic system that can be used to implement photonic logic functions. Additionally, all-optical photonic processing is achieved using the cavity-mode shift produced in the injected slave laser under external optical injection. The inverting logic case can also be used as a wavelength converter — a key component in advanced wavelength-division multiplexing networks. As a result of this experimental investigation, a more comprehensive understanding of the locking parameters involved in injecting multiple lasers into a multi-mode cavity and the logic transition time is achieved. The performance of optical logic computations and wavelength conversion has the potential for ultrafast operation, limited primarily by the photon decay rate in the slave laser.

  12. Bistable Si dopants in the GaAs (1 1 0) surface

    International Nuclear Information System (INIS)

    Smakman, E P; Koenraad, P M

    2015-01-01

    In this review, recent work is discussed on bistable Si dopants in the GaAs (1 1 0) surface, studied by scanning tunneling microscopy (STM). The bistability arises because the dopant atom can switch between a positive and a negative charge state, which are associated with two different lattice configurations. Manipulation of the Si atom charge configuration is achieved by tuning the local band bending with the STM tip. Furthermore, illuminating the sample with a laser also influences the charge state, allowing the operation of the dopant atom as an optical switch. The switching dynamics without illumination is investigated in detail as a function of temperature, lateral tip position, and applied tunneling conditions. A physical model is presented that independently describes the thermal and quantum tunneling contributions to the switching frequency and charge state occupation of a single Si atom. The basic functionality of a memory cell is demonstrated employing a single bistable Si dopant as the active element, using the STM tip as a gate to write and read the information. (topical review)

  13. Semiconductor statistics

    CERN Document Server

    Blakemore, J S

    1987-01-01

    In-depth exploration of the implications of carrier populations and Fermi energies examines distribution of electrons in energy bands and impurity levels of semiconductors. Also: kinetics of semiconductors containing excess carriers, particularly in terms of trapping, excitation, and recombination.

  14. An ultra-long cavity passively mode-locked fiber laser based on nonlinear polarization rotation in a semiconductor optical amplifier

    International Nuclear Information System (INIS)

    Liu, Tonghui; Jia, Dongfang; Yang, Jingwen; Chen, Jiong; Wang, Zhaoying; Yang, Tianxin

    2013-01-01

    In this paper we investigate an ultra-long cavity passively mode-locked fiber laser based on a semiconductor optical amplifier (SOA). Experimental results are presented which indicate that stable mode-locked pulses can be obtained by combining nonlinear polarization rotation (NPR) in the SOA with a polarization controller. By adding a 4 km single mode fiber into the ring cavity, a stable fundamental-order mode-locked pulse train with a repetition rate of 50.72 kHz is generated through the NPR effect in the SOA. The central wavelength, 3 dB bandwidth and single pulse energy of the output pulse are 1543.95 nm, 1.506 nm and 33.12 nJ, respectively. Harmonic mode-locked pulses are also observed in experiments when the parameters are chosen properly. (paper)

  15. Semiconductor-based narrow-line and high-brilliance 193-nm laser system for industrial applications

    Science.gov (United States)

    Opalevs, D.; Scholz, M.; Stuhler, J.; Gilfert, C.; Liu, L. J.; Wang, X. Y.; Vetter, A.; Kirner, R.; Scharf, T.; Noell, W.; Rockstuhl, C.; Li, R. K.; Chen, C. T.; Voelkel, R.; Leisching, P.

    2018-02-01

    We present a novel industrial-grade prototype version of a continuous-wave 193 nm laser system entirely based on solid state pump laser technology. Deep-ultraviolet emission is realized by frequency-quadrupling an amplified diode laser and up to 20 mW of optical power were generated using the nonlinear crystal KBBF. We demonstrate the lifetime of the laser system for different output power levels and environmental conditions. The high stability of our setup was proven in > 500 h measurements on a single spot, a crystal shifter multiplies the lifetime to match industrial requirements. This laser improves the relative intensity noise, brilliance, wall-plug efficiency and maintenance cost significantly. We discuss first lithographic experiments making use of this improvement in photon efficiency.

  16. Steady state statistical correlations predict bistability in reaction motifs.

    Science.gov (United States)

    Chakravarty, Suchana; Barik, Debashis

    2017-03-28

    Various cellular decision making processes are regulated by bistable switches that take graded input signals and convert them to binary all-or-none responses. Traditionally, a bistable switch generated by a positive feedback loop is characterized either by a hysteretic signal response curve with two distinct signaling thresholds or by characterizing the bimodality of the response distribution in the bistable region. To identify the intrinsic bistability of a feedback regulated network, here we propose that bistability can be determined by correlating higher order moments and cumulants (≥2) of the joint steady state distributions of two components connected in a positive feedback loop. We performed stochastic simulations of four feedback regulated models with intrinsic bistability and we show that for a bistable switch with variation of the signal dose, the steady state variance vs. covariance adopts a signatory cusp-shaped curve. Further, we find that the (n + 1)th order cross-cumulant vs. nth order cross-cumulant adopts a closed loop structure for at least n = 3. We also propose that our method is capable of identifying systems without intrinsic bistability even though the system may show bimodality in the marginal response distribution. The proposed method can be used to analyze single cell protein data measured at steady state from experiments such as flow cytometry.

  17. Bubbling and bistability in two parameter discrete systems

    OpenAIRE

    Ambika, G.; Sujatha, N. V.

    2000-01-01

    We present a graphical analysis of the mechanisms underlying the occurrences of bubbling sequences and bistability regions in the bifurcation scenario of a special class of one dimensional two parameter maps. The main result of the analysis is that whether it is bubbling or bistability is decided by the sign of the third derivative at the inflection point of the map function.

  18. Bistable soliton states and switching in doubly inhomogeneously ...

    Indian Academy of Sciences (India)

    Dec. 2001 physics pp. 969–979. Bistable soliton states and switching in doubly inhomogeneously doped fiber couplers. AJIT KUMAR. Department of Physics, Indian Institute of Technology, Hauz Khas, New Delhi 110 016, India. Abstract. Switching between the bistable soliton states in a doubly and inhomogeneously doped.

  19. Multistability in Bistable Ferroelectric Materials toward Adaptive Applications

    NARCIS (Netherlands)

    Ghosh, Anirban; Koster, Gertjan; Rijnders, Augustinus J.H.M.

    2016-01-01

    Traditionally thermodynamically bistable ferroic materials are used for nonvolatile operations based on logic gates (e.g., in the form of field effect transistors). But, this inherent bistability in these class of materials limits their applicability for adaptive operations. Emulating biological

  20. Semiconductor physics

    CERN Document Server

    Böer, Karl W

    2018-01-01

    This handbook gives a complete survey of the important topics and results in semiconductor physics. It addresses every fundamental principle and most research topics and areas of application in the field of semiconductor physics. Comprehensive information is provided on crystalline bulk and low-dimensional as well as amporphous semiconductors, including optical, transport, and dynamic properties.

  1. Optical bistability using quantum interference in V-type atoms

    International Nuclear Information System (INIS)

    Anton, M A; Calderon, Oscar G

    2002-01-01

    The behaviour of a V-type three-level atomic system in a ring cavity driven by a coherent field is studied. We consider a V configuration under conditions such that interference between decay channels is important. We find that when quantum interference is taken into account, optical bistability can be realized with a considerable decrease in the threshold intensity and the cooperative parameter. On the other hand, we also include the finite bandwidth of the driving field and study its role in the optical bistable response. It is found that at certain linewidths of the driving field optical bistability is obtained even if the system satisfies the trapping condition and the threshold intensity can be controlled. Furthermore, a change from the optical bistability due to quantum interference to the usual bistable behaviour based on saturation occurs as the driving field linewidth increases

  2. A hierarchical stochastic model for bistable perception.

    Directory of Open Access Journals (Sweden)

    Stefan Albert

    2017-11-01

    Full Text Available Viewing of ambiguous stimuli can lead to bistable perception alternating between the possible percepts. During continuous presentation of ambiguous stimuli, percept changes occur as single events, whereas during intermittent presentation of ambiguous stimuli, percept changes occur at more or less regular intervals either as single events or bursts. Response patterns can be highly variable and have been reported to show systematic differences between patients with schizophrenia and healthy controls. Existing models of bistable perception often use detailed assumptions and large parameter sets which make parameter estimation challenging. Here we propose a parsimonious stochastic model that provides a link between empirical data analysis of the observed response patterns and detailed models of underlying neuronal processes. Firstly, we use a Hidden Markov Model (HMM for the times between percept changes, which assumes one single state in continuous presentation and a stable and an unstable state in intermittent presentation. The HMM captures the observed differences between patients with schizophrenia and healthy controls, but remains descriptive. Therefore, we secondly propose a hierarchical Brownian model (HBM, which produces similar response patterns but also provides a relation to potential underlying mechanisms. The main idea is that neuronal activity is described as an activity difference between two competing neuronal populations reflected in Brownian motions with drift. This differential activity generates switching between the two conflicting percepts and between stable and unstable states with similar mechanisms on different neuronal levels. With only a small number of parameters, the HBM can be fitted closely to a high variety of response patterns and captures group differences between healthy controls and patients with schizophrenia. At the same time, it provides a link to mechanistic models of bistable perception, linking the group

  3. A hierarchical stochastic model for bistable perception.

    Science.gov (United States)

    Albert, Stefan; Schmack, Katharina; Sterzer, Philipp; Schneider, Gaby

    2017-11-01

    Viewing of ambiguous stimuli can lead to bistable perception alternating between the possible percepts. During continuous presentation of ambiguous stimuli, percept changes occur as single events, whereas during intermittent presentation of ambiguous stimuli, percept changes occur at more or less regular intervals either as single events or bursts. Response patterns can be highly variable and have been reported to show systematic differences between patients with schizophrenia and healthy controls. Existing models of bistable perception often use detailed assumptions and large parameter sets which make parameter estimation challenging. Here we propose a parsimonious stochastic model that provides a link between empirical data analysis of the observed response patterns and detailed models of underlying neuronal processes. Firstly, we use a Hidden Markov Model (HMM) for the times between percept changes, which assumes one single state in continuous presentation and a stable and an unstable state in intermittent presentation. The HMM captures the observed differences between patients with schizophrenia and healthy controls, but remains descriptive. Therefore, we secondly propose a hierarchical Brownian model (HBM), which produces similar response patterns but also provides a relation to potential underlying mechanisms. The main idea is that neuronal activity is described as an activity difference between two competing neuronal populations reflected in Brownian motions with drift. This differential activity generates switching between the two conflicting percepts and between stable and unstable states with similar mechanisms on different neuronal levels. With only a small number of parameters, the HBM can be fitted closely to a high variety of response patterns and captures group differences between healthy controls and patients with schizophrenia. At the same time, it provides a link to mechanistic models of bistable perception, linking the group differences to

  4. Tunable Injection Barrier in Organic Resistive Switches Based on Phase-Separated Ferroelectric-Semiconductor Blends

    NARCIS (Netherlands)

    Asadi, Kamal; de Boer, Tom G.; Blom, Paul W. M.; de Leeuw, Dago M.

    2009-01-01

    Organic non-volatile resistive bistable diodes based on phase-separated blends of ferroelectric and semiconducting polymers are fabricated. The polarization field of the ferroelectric modulates the injection barrier at the semiconductor-electrode contact and, hence, the resistance of the comprising

  5. Tunable injection barrier in organic resistive switches based on phase-separated ferroelectric-semiconductor blends

    NARCIS (Netherlands)

    Asadi, K.; Boer, T.G. de; Blom, P.W.M.; Leeuw, D.M. de

    2009-01-01

    Organic non-volatile resistive bistable diodes based on phase-separated blends of ferroelectric and semiconducting polymers are fabricated. The polarization field of the ferroelectric modulates the injection barrier at the semiconductor-electrode contact and, hence, the resistance of the comprising

  6. Semiconductor opto-electronics

    CERN Document Server

    Moss, TS; Ellis, B

    1972-01-01

    Semiconductor Opto-Electronics focuses on opto-electronics, covering the basic physical phenomena and device behavior that arise from the interaction between electromagnetic radiation and electrons in a solid. The first nine chapters of this book are devoted to theoretical topics, discussing the interaction of electromagnetic waves with solids, dispersion theory and absorption processes, magneto-optical effects, and non-linear phenomena. Theories of photo-effects and photo-detectors are treated in detail, including the theories of radiation generation and the behavior of semiconductor lasers a

  7. Diode lasers and arrays

    International Nuclear Information System (INIS)

    Streifer, W.

    1988-01-01

    This paper discusses the principles of operation of III-V semiconductor diode lasers, the use of distributed feedback, and high power laser arrays. The semiconductor laser is a robust, miniature, versatile device, which directly converts electricity to light with very high efficiency. Applications to pumping solid-state lasers and to fiber optic and point-to-point communications are reviewed

  8. An ultra-wideband tunable multi-wavelength Brillouin fibre laser based on a semiconductor optical amplifier and dispersion compensating fibre in a linear cavity configuration

    International Nuclear Information System (INIS)

    Zulkifli, M Z; Ahmad, H; Hassan, N A; Jemangin, M H; Harun, S W

    2011-01-01

    A multi-wavelength Brillouin fibre laser (MBFL) with an ultra-wideband tuning range from 1420 nm to 1620 nm is demonstrated. The MBFL uses an ultra-wideband semiconductor optical amplifier (SOA) and a dispersion compensating fibre (DCF) as the linear gain medium and nonlinear gain medium, respectively. The proposed MBFL has a wide tuning range covering the short (S-), conventional (C-) and long (L-) bands with a wavelength spacing of 0.08 nm, making it highly suitable for DWDM system applications. The output power of the observed Brillouin Stokes ranges approximately from -5.94 dBm to -0.41 dBm for the S-band, from -4.34 dBm to 0.02 dBm for the C-band and from -2.19 dBm to 0.39 dBm for the L-band. The spacing between each adjacent wavelengths of all the three bands is about 0.08 nm, which is approximately 10.7 GHz for the frequency domain. (lasers)

  9. Mid-infrared Fe2+:ZnSe semiconductor saturable absorber mirror for passively Q-switched Er3+-doped ZBLAN fiber laser

    Directory of Open Access Journals (Sweden)

    Shougui Ning

    2018-02-01

    Full Text Available A mid-infrared (mid-IR semiconductor saturable absorber mirror (SESAM based on Fe2+:ZnSe for passively Q-switched Er3+-doped ZBLAN fiber laser has been demonstrated. Fe2+:ZnSe SESAM was fabricated by electron beam evaporation method. Fe2+ was innovatively doped into the reflective Bragg stack, in which ZnSe layer served as both doped matrix and high refractive layer during the fabricating process. By using the Fe2+:ZnSe SESAM, stable passively Q-switched pulses with the minimum pulse width of 0.43 μs under a repetition rate of 160.82 kHz were obtained. The recorded maximum average output power of 873 mW with a peak power of 12.59 W and pulse energy of 5.43 μJ were achieved. The results demonstrated a new method for fabricating Fe2+:ZnSe SESAM, which can be used in compact mid-IR Q-switched fiber laser.

  10. ZnCdMgSe as a Materials Platform for Advanced Photonic Devices: Broadband Quantum Cascade Detectors and Green Semiconductor Disk Lasers

    Science.gov (United States)

    De Jesus, Joel

    The ZnCdMgSe family of II-VI materials has unique and promising characteristics that may be useful in practical applications. For example they can be grown lattice matched to InP substrates with lattice matched bandgaps that span from 2.1 to 3.5 eV, they can be successfully doped n-type, have a large conduction band offset (CBO) with no intervalley scattering present when strained, they have lower average phonon energies, and the InP lattice constant lies in the middle of the ZnSe and CdSe binaries compounds giving room to experiment with tensile and compressive stress. However they have not been studied in detail for use in practical devices. Here we have identified two types of devices that are being currently developed that benefit from the ZnCdMgSe-based material properties. These are the intersubband (ISB) quantum cascade (QC) detectors and optically pumped semiconductor lasers that emit in the visible range. The paucity for semiconductor lasers operating in the green-orange portion of the visible spectrum can be easily overcome with the ZnCdMgSe materials system developed in our research. The non-strain limited, large CBO available allows to expand the operating wavelength of ISB devices providing shorter and longer wavelengths than the currently commercially available devices. This property can also be exploited to develop broadband room temperature operation ISB detectors. The work presented here focused first on using the ZnCdMgSe-based material properties and parameter to understand and predict the interband and intersubband transitions of its heterostructures. We did this by studying an active region of a QC device by contactless electroreflectance, photoluminescence, FTIR transmittance and correlating the measurements to the quantum well structure by transfer matrix modeling. Then we worked on optimizing the ZnCdMgSe material heterostructures quality by studying the effects of growth interruptions on their optical and optoelectronic properties of

  11. Blue 450nm high power semiconductor continuous wave laser bars exceeding rollover output power of 80W

    Science.gov (United States)

    König, H.; Lell, A.; Stojetz, B.; Ali, M.; Eichler, C.; Peter, M.; Löffler, A.; Strauss, U.; Baumann, M.; Balck, A.; Malchus, J.; Krause, V.

    2018-02-01

    Industrial material processing like cutting or welding of metals is rather energy efficient using direct diode or diode pumped solid state lasers. However, many applications cannot be addressed by established infrared laser technology due to fundamental material properties of the workpiece: For example materials like copper or gold have too low absorption in the near infrared wavelength range to be processed efficiently by use of existing high power laser systems. The huge interest to enable high power kW systems with more suitable wavelengths in the blue spectral range triggered the German funded research project 'BLAULAS': Therein the feasibility and capability of CW operating high power laser bars based on the GaN material system was investigated by Osram and Laserline. High performance bars were enabled by defeating fundamental challenges like material quality as well as the chip processes, both of which differ significantly from well-known IR laser bars. The research samples were assembled on actively cooled heat sinks with hard solder technology. For the first time an output power of 98W per bar at 60A drive current was achieved. Conversion efficiency as high as 46% at 50W output power was demonstrated.

  12. On the bistable zone of milling processes.

    Science.gov (United States)

    Dombovari, Zoltan; Stepan, Gabor

    2015-09-28

    A modal-based model of milling machine tools subjected to time-periodic nonlinear cutting forces is introduced. The model describes the phenomenon of bistability for certain cutting parameters. In engineering, these parameter domains are referred to as unsafe zones, where steady-state milling may switch to chatter for certain perturbations. In mathematical terms, these are the parameter domains where the periodic solution of the corresponding nonlinear, time-periodic delay differential equation is linearly stable, but its domain of attraction is limited due to the existence of an unstable quasi-periodic solution emerging from a secondary Hopf bifurcation. A semi-numerical method is presented to identify the borders of these bistable zones by tracking the motion of the milling tool edges as they might leave the surface of the workpiece during the cutting operation. This requires the tracking of unstable quasi-periodic solutions and the checking of their grazing to a time-periodic switching surface in the infinite-dimensional phase space. As the parameters of the linear structural behaviour of the tool/machine tool system can be obtained by means of standard modal testing, the developed numerical algorithm provides efficient support for the design of milling processes with quick estimates of those parameter domains where chatter can still appear in spite of setting the parameters into linearly stable domains. © 2015 The Authors.

  13. Single coil bistable, bidirectional micromechanical actuator

    Science.gov (United States)

    Tabat, Ned; Guckel, Henry

    1998-09-15

    Micromechanical actuators capable of bidirectional and bistable operation can be formed on substrates using lithographic processing techniques. Bistable operation of the microactuator is obtained using a single coil and a magnetic core with a gap. A plunger having two magnetic heads is supported for back and forth linear movement with respect to the gap in the magnetic core, and is spring biased to a neutral position in which the two heads are on each side of the gap in the core. The single electrical coil is coupled to the core and is provided with electrical current to attract one of the heads toward the core by reluctance action to drive the plunger to a limit of travel in one direction. The current is then cut off and the plunger returns by spring action toward the gap, whereafter the current is reapplied to the coil to attract the other head of the plunger by reluctance action to drive the plunger to its other limit of travel. This process can be repeated at a time when switching of the actuator is required.

  14. Deployable structures using bistable reeled composites

    Science.gov (United States)

    Daton-Lovett, Andrew J.; Compton-Bishop, Quentin M.; Curry, Richard G.

    2000-06-01

    This paper describes an innovative, patented use of composite materials developed by RolaTube Technology Ltd. to make smart deployable structures. Bi-stable reeled composites (BRCs) can alternate between two stable forms; that of a strong, rigid structure and that of a compact coil of flat-wound material. Bi-stability arises as a result of the manipulation of Poisson's ratio and isotropy in the various layers of the material. BRCs are made of fiber- reinforced composite materials, most often with a thermoplastic matrix. A range of fibers and polymer matrices can be used according to the requirements of the operating environment. Samples of a BRC structure were constructed using layers of unidirectional, fiber-reinforced thermoplastic sheet with the layers at different angles. The whole assembly was then consolidated under conditions of elevated temperature and pressure. The properties of the BRC are described and the result of a series of experiments performed on the sample to determine the tensile strength of the BRC structure are reported. A full analysis using finite element methods is being undertaken in collaboration with the University of Cambridge, England. The first commercial use has been to fabricate boom and drive mechanisms for the remote inspection of industrial plant.

  15. Laser-based irradiation apparatus and methods for monitoring the dose-rate response of semiconductor devices

    Science.gov (United States)

    Horn, Kevin M [Albuquerque, NM

    2006-03-28

    A scanned, pulsed, focused laser irradiation apparatus can measure and image the photocurrent collection resulting from a dose-rate equivalent exposure to infrared laser light across an entire silicon die. Comparisons of dose-rate response images or time-delay images from before, during, and after accelerated aging of a device, or from periodic sampling of devices from fielded operational systems allows precise identification of those specific age-affected circuit structures within a device that merit further quantitative analysis with targeted materials or electrical testing techniques. Another embodiment of the invention comprises a broad-beam, dose rate-equivalent exposure apparatus. The broad-beam laser irradiation apparatus can determine if aging has affected the device's overall functionality. This embodiment can be combined with the synchronized introduction of external electrical transients into a device under test to simulate the electrical effects of the surrounding circuitry's response to a radiation exposure.

  16. Ca++ dependent bistability induced by serotonin in spinal motoneurons

    DEFF Research Database (Denmark)

    Hounsgaard, J.; Kiehn, O.

    1985-01-01

    The plateau potential, responsible for the bistable state of spinal motoneurons, recently described in the decerebrate cat, was suggested to depend on serotonin (Hounsgaard et al. 1984). In an in vitro preparation of the spinal cord of the turtle we now show that serotonin, applied directly...... to the bath, transforms the intrinsic response properties of motoneurons, uncovering a plateau potential and voltage sensitive bistability. The changes induced by serotonin were blocked by Mn++, while the plateau potential and the bistability remained after application of tetrodotoxin. We conclude...... that serotonin controls the expression of a Ca++ dependent plateau potential in motoneurons....

  17. Growth and characterization of ZnCdMgSe-based green light emitters and distributed Bragg reflectors towards II-VI based semiconductor disk lasers

    International Nuclear Information System (INIS)

    De Jesus, Joel; Gayen, Swapan K.; Garcia, Thor A.; Tamargo, Maria C.; Kartazaev, Vladimir; Jones, Brynmor E.; Schlosser, Peter J.; Hastie, Jennifer E.

    2015-01-01

    We report the structural and optical properties of molecular beam epitaxy grown II-VI semiconductor multiple quantum well (MQW) structures and distributed Bragg reflector (DBR) on InP substrates for application in developing optically-pumped semiconductor disk lasers (SDLs) operating in the green spectral range. One sample was grown directly on an InP substrate with an InGaAs buffer layer, while another had a 5-period ZnCdMgSe-based DBR grown on the InGaAs/InP substrate. X-ray diffraction and scanning electron microscopy measurements revealed sharp superlattice peaks and abrupt layer interfaces, while steady-state photoluminescence measurements demonstrated surface emission between 540-570 nm. Under pulsed excitation both samples exhibited features of amplified spontaneous emission (ASE) or stimulated emission, accompanied by luminescence lifetime shortening. The sample with the DBR showed higher surface luminescence and the onset of ASE at lower pump power. To further explore the design and performance of a ZnCdMgSe-based DBR, a 20-period DBR was grown and a reflectivity of 83% was obtained at ∝560 nm. We estimate that a DBR with ∝40 periods would be needed for optimal performance in a SDL using these materials. These results show the potential of II-VI MQW structures on InP substrates for the development of SDLs operational in the green-yellow wavelength range. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Investigations of repetition rate stability of a mode-locked quantum dot semiconductor laser in an auxiliary optical fiber cavity

    DEFF Research Database (Denmark)

    Breuer, Stefan; Elsässer, Wolfgang; McInerney, J.G.

    2010-01-01

    We have investigated experimentally the pulse train (mode beating) stability of a monolithic mode-locked multi-section quantum-dot laser with an added passive auxiliary optical fiber cavity. Addition of the weakly coupled (¿ -24dB) cavity reduces the current-induced shift d¿/dI of the principal...

  19. Laser induced local structural and property modifications in semiconductors for electronic and photonic superstructures - Silicon carbide to graphene conversion

    Science.gov (United States)

    Yue, Naili

    Graphene is a single atomic layer two-dimensional (2D) hexagonal crystal of carbon atoms with sp2-bonding. Because of its various special or unique properties, graphene has attracted huge attention and considerable interest in recent years. This PhD research work focuses on the development of a novel approach to fabricating graphene micro- and nano-structures using a 532 nm Nd:YAG laser, a technique based on local conversion of 3C-SiC thin film into graphene. Different from other reported laser-induced graphene on single crystalline 4H- or 6H- SiC, this study focus on 3C-SiC polycrystal film grown using MBE. Because the SiC thin film is grown on silicon wafer, this approach may potentially lead to various new technologies that are compatible with those of Si microelectronics for fabricating graphene-based electronic, optoelectronic, and photonic devices. The growth conditions for depositing 3C-SiC using MBE on Si wafers with three orientations, (100), (110), and (111), were evaluated and explored. The surface morphology and crystalline structure of 3C-SiC epilayer were investigated with SEM, AFM, XRD, μ-Raman, and TEM. The laser modification process to convert 3C-SiC into graphene layers has been developed and optimized by studying the quality dependence of the graphene layers on incident power, irradiation time, and surface morphology of the SiC film. The laser and power density used in this study which focused on thin film SiC was compared with those used in other related research works which focused on bulk SiC. The laser-induced graphene was characterized with μ-Raman, SEM/EDS, TEM, AFM, and, I-V curve tracer. Selective deposition of 3C-SiC thin film on patterned Si substrate with SiO2 as deposition mask has been demonstrated, which may allow the realization of graphene nanostructures (e.g., dots and ribbons) smaller than the diffraction limit spot size of the laser beam, down to the order of 100 nm. The electrical conductance of directly written graphene

  20. Ultrafast supercontinuum fiber-laser based pump-probe scanning magneto-optical Kerr effect microscope for the investigation of electron spin dynamics in semiconductors at cryogenic temperatures with picosecond time and micrometer spatial resolution.

    Science.gov (United States)

    Henn, T; Kiessling, T; Ossau, W; Molenkamp, L W; Biermann, K; Santos, P V

    2013-12-01

    We describe a two-color pump-probe scanning magneto-optical Kerr effect microscope which we have developed to investigate electron spin phenomena in semiconductors at cryogenic temperatures with picosecond time and micrometer spatial resolution. The key innovation of our microscope is the usage of an ultrafast "white light" supercontinuum fiber-laser source which provides access to the whole visible and near-infrared spectral range. Our Kerr microscope allows for the independent selection of the excitation and detection energy while avoiding the necessity to synchronize the pulse trains of two separate picosecond laser systems. The ability to independently tune the pump and probe wavelength enables the investigation of the influence of excitation energy on the optically induced electron spin dynamics in semiconductors. We demonstrate picosecond real-space imaging of the diffusive expansion of optically excited electron spin packets in a (110) GaAs quantum well sample to illustrate the capabilities of the instrument.