Showing papers on "Semiconductor optical gain published in 1981"
252 citations
TL;DR: In this paper, a theory for the steady-state behavior of the external-cavity semiconductor laser taking into account such coherent optical effects is developed, and the inclusion of these effects is also important in the interpretation of the threshold data of such lasers.
Abstract: A broadening of the apparent linewidth of the semiconductor laser modes with external optical feedback is observed. This is shown to be due to the coherent nature of the feedback and multiple reflections in the external cavity. A theory for the steady-state behavior of the external-cavity semiconductor laser taking into account such coherent optical effects is developed. The inclusion of these effects is also important in the interpretation of the threshold data of such lasers.
132 citations
27 Apr 1981
TL;DR: In this paper, the noise of semiconductor laser light after passing a Michelson interferometer has been measured for gain guided as well as index guided double-heterostructure injection lasers.
Abstract: The noise of semiconductor laser light after passing a Michelson interferometer has been measured for gain guided as well as index guided double-heterostructure injection lasers. This noise is mainly due to the partition noise and the frequency noise of the laser emission. Unless the interferometer is perfectly balanced, the observed noise is several orders of magnitude larger than the usual intensity noise of semiconductor lasers.
106 citations
TL;DR: The history of modelocking of the semiconductor laser is reviewed in this paper, where the theory of model-checking as it relates to the SLL diode system is developed and discussed.
Abstract: The history of modelocking of the semiconductor laser is reviewed. The theory of modelocking as it relates to the semiconductor laser diode system is developed and discussed. Experiments on semiconductor lasers at MIT and the Bell Laboratories under both active and passive modelocking conditions are described.
71 citations
Patent•
03 Mar 1981TL;DR: In this article, a method for the conversion of a non-single crystalline semiconductor to a single-layer single-crystal semiconductor using an energy ray irradiation process was proposed.
Abstract: Various improvements applicable to a method for production of a semiconductor device which is produced on a single crystalline semiconductor layer converted from a non-single crystalline semiconductor layer employing an energy ray irradiation process for conversion of non-single crystalline semiconductor to single crystalline semiconductor, including a process to make a scribing process more efficient realized by producing windows along scribe lines, a process for production of a planer type semiconductor device without damaging a converted single crystalline semiconductor layer realized by interposition of a field oxidation process and an energy ray irradiation process, a process enabling deep and uniform distribution of impurities without lateral diffusion in a semiconductor layer and a process for production of an embedded semiconductor resistor realized by employment of a mask made of a material not to allow radiated heat to pass therethrough, and a process for production of a mesa type semiconductor device not to allow discontinuity of wirings realized by employment of an energy ray irradiation process.
62 citations
TL;DR: In this article, the results of experimental and theoretical analyses on the voltage changes across the GaAlAs semiconductor laser diodes caused by the onset of optical feedback are described.
Abstract: The results of experimental and theoretical analyses on the voltage changes across the GaAlAs semiconductor laser diodes caused by the onset of optical feedback are described. The dependence of voltage changes on the injection current and on the feedback ratio indicates that the origins of the voltage changes are the photoconduction effect and a reduction of the quasi-Fermi level related to the enhanced stimulated emission. The calculated voltage changes based on the theoretical analyses using the published laser parameters are in good agreement with the experimental ones. The preferable specifications for a laser diode (LD) to exhibit a larger voltage change at the onset of optical feedback are discussed.
59 citations
TL;DR: In this paper, a simple analytical expression for the reflectivity of the cleaved facets of DH semiconductor lasers is compared with numerical results, and reasonable agreement is found. But the analytical result is conveniently written in terms of waveguide parameters and thus gives a valuable tool for analysis of DH lasers.
Abstract: A simple analytical expression for the reflectivity of the cleaved facets of DH semiconductor lasers is compared with numerical results, and reasonable agreement is found. The analytical result is conveniently written in terms of waveguide parameters and thus gives a valuable tool for analysis of DH lasers.
49 citations
TL;DR: In this paper, an incident optical beam, generated by a conventional DH semiconductor laser, was injected into the InP/InGaAsP DH laser with inhomogeneous excitation.
Abstract: Bistable operation in InP/InGaAsP DH lasers by optical injection is reported for the first time. An incident optical beam, generated by a conventional DH semiconductor laser, was injected into the semiconductor laser with inhomogeneous excitation. Bistability has been achieved in the relation between input intensity of the incident beam and the optical output intensity of the inhomogeneously excited laser. The bistable laser also acts as an optical limiter, i.e. the optical output completely saturates above the laser threshold level.
42 citations
TL;DR: The spontaneous emission factor of narrow-stripe gain-guided diode lasers was shown to be one order of magnitude greater than previously supposed in this article, which is of importance in determining time-response and longitudinal-mode structure.
Abstract: The spontaneous emission factor of narrow-stripe gain-guided diode lasers, which is of importance in determining time-response and longitudinal-mode structure, is shown to be one order of magnitude greater than previously supposed.
38 citations
TL;DR: In this article, a red shift in the diode modes with increasing optical feedback is observed in external cavity AlxGa1−xAs injection laser, due to a change in the refractive index in the active region resulting from a reduction in the populationinversion induced by the optical feedback.
Abstract: A red‐shift in the diode modes with increasing optical feedback is observed in external‐cavity AlxGa1−xAs injection lasers. This shift is due to a change in the refractive index in the active region resulting from a reduction in the population‐inversion induced by the optical feedback. This leads to a new determination of the carrier dependence of the refractive index at the laser wavelength in the active region of semiconductor lasers independent of current‐induced thermal effects.
36 citations
TL;DR: In this article, the authors measured the width of the optical beam in the plane of the junction as a function of time during a pulse and found that the width increases during the quiescent period between pulses where the carrier density increases by current injection and decreases during the emission of the pulse.
Abstract: Using proton bombarded stripe geometry lasers which emit intense optical pulses, we have measured the width of the optical beam in the plane of the junction as a function of time during the pulse. The width of the beam is qualitatively proportional to the change in the carrier density. The width increases during the quiescent period between pulses where the carrier density increases by current injection and decreases during the emission of the pulse. For one laser studied in considerable detail, the full width at half intensity decreases from 9 μm at the start of the pulse to 7.2 μm at the end of the pulse. The reduction in the width results from the self-focusing of the beam. It is due to an increase in the refractive index and the decrease in the gain distributions near the center of the stripe. The reduction in the beamwidth concentrates the mode to a region of sufficiently higher average gain to compensate for the reduction in spatial gain distribution. The self-focusing acts to reduce the damping of the relaxation oscillations, and thus enhances the effect of other nonlinearities such as saturable absorption in causing pulsations. The thermal induced refractive index distribution across the stripe is shown to play a crucial role in the gain instability caused by self-focusing.
TL;DR: In this article, the present status of mode-stabilized semiconductor injection lasers emitting in the 0.8-0.9 and 1.1-1.6 \mu m wavelength regions are described.
Abstract: The present status of mode-stabilized semiconductor injection lasers emitting in the 0.8-0.9 and 1.1-1.6 \mu m wavelength regions are described. The double-heterostructure GaAlAs/GaAs and InGaAsP/ InP crystals have been developed. Transverse-mode stabilization by means of gain guiding or index guiding is a key issue to realized high linearity, low noise operation. The mode-stabilized laser structures as well as the corresponding lasing characteristics are shown in detail. Longitudinal mode control is possible by grating feedback, but the fabrication technology is still immature. Reliability of the mode-stabilized lasers is also mentioned.
TL;DR: In this paper, the temporal dependence of the frequency shift in a single-mode semiconductor laser was measured and compared with calculations based on solutions to the thermal diffusion equation, and the effects of carrier density change, thermal diffusion in the semiconductor, and heat sink thermal resistance were identified.
Abstract: The temporal dependence of the frequency shift in a current-modulated single-mode semiconductor laser is measured and compared with calculations based on solutions to the thermal diffusion equation. The effects of carrier density change, thermal diffusion in the semiconductor, and heat sink thermal resistance are identified.
TL;DR: In this article, a bistable optical device consisting of a semiconductor laser diode and a photodetector has been experimentally demonstrated for the first time, and the operational principle graphically is described to explain the observed effects such as hysteresis and differential gain.
Abstract: A novel bistable optical device simply consisting of a semiconductor laser diode and a photodetector has been experimentally demonstrated for the first time. We describe the operational principle graphically to explain the observed effects such as hysteresis and differential gain. The development of its monolithically integrated version will lead to a number of fascinating and useful applications.
TL;DR: In this paper, the authors obtained 6-8 ps in an actively mode-locked external-cavity antireflection (AR) coated semiconductor laser, and reported the mode locking of a ring-Cavity semiconductor LM.
Abstract: Pulses on the order of 6-8 ps are obtained in an actively mode-locked external-cavity antireflection (AR) coated semiconductor laser. We also report the mode locking of a ring-cavity semiconductor laser.
TL;DR: In this paper, the noise characteristics of Fabry-Perot (FP) cavity type AlGaAs laser amplifiers are studied theoretically and experimentally, and the noise power dependencies on pumping rate and input signal level are measured.
Abstract: Noise characteristics of Fabry-Perot (FP) cavity type AlGaAs laser amplifiers are studied theoretically and experimentally. Noise power dependencies on pumping rate and input signal level are measured. Multimode rate equations with McCumber's fluctuation operator are solved for the parabolic band and the exponential bandtail models, both with the no k-selection rule. Experimental results are in good agreement with theoretical predictions.
TL;DR: In this article, the four-photon interactions involving both a two-and a onephoton resonance with an np2P level (n = 7-10 ) are investigated in detail.
Abstract: Four-photon interactions involving both a two-photon resonance with the 9d^{2}D_{3/2} level and a one-photon resonance with an np2P level ( n = 7-10 ) are investigated in detail. Gain, gain saturation, gain threshold, and forward-to-backward generation ratios are measured. Comparison with numerical estimates indicates that 9d^{2}D_{3/2} to np^{2}P lasing is the dominant gain mechanism but that a doubly resonant four-photon parametric oscillation makes a significant contribution. Gain saturation is dominated by population of np2P levels. Ionization is important, especially at higher pump powers.
TL;DR: In this article, the optical coupling of two injection lasers was used to study the gain broadening mechanism for three different types of laser structures: proton bombarded stripe geometry, V -groove, and channeled substrate planar stripe (CSP) lasers.
Abstract: A new type of experiment, the optical coupling of two injection lasers, is presented. This method is used to study the gain broadening mechanism for three different types of laser structures: proton bombarded stripe geometry, V -groove, and channeled substrate planar stripe (CSP) lasers. The gain reduction in the presence of a strong injected light is detected with high sensitivity by a differential measurement. Independent of the laser structure, the homogeneous gain broadening mechanism is by far dominating.
25 Feb 1981
TL;DR: In this paper, an automatic frequency control system for GaAkAs semiconductor lasers is described, where the frequency drift can be reduced to below 10 MHz and without sacri ficing the frequency stability, a tunable frequency range of 0.5 THz is obtained.
Abstract: Heterodyne-type optical communication will provide a wide bandwidth and a high signal-to-noise ratio. However, at present the frequency drift of semiconductor lasers is the greatest difficulty, which must be overcome before the heterodyne-type communication is realized. This paper describes an automatic frequency control system for GaAkAs semiconductor lasers. The frequency drift can be reduced to below 10 MHz. Besides, without sacri ficing the frequency stability, a tunable frequency range of 0.5 THz is obtained. These values are good enough for heterodyne-type optical communication systems.
Patent•
26 Oct 1981TL;DR: In this article, a spatial filter in the cavity between the optical gain element array and the reflectors is used to establish spatial coherence of the light within the cavity to establish a coherent output beam.
Abstract: An external cavity semiconductor laser includes an array of semiconductor optical gain elements, each device having at least one transmissive facet along an optical axis, and reflectors for reflecting incident light from the laser devices back to those devices. Optical fibers couple the transmissive facets of the optical gain elements in parallel to the reflectors. A spatial filter in the cavity between the optical gain element array and the reflectors establish spatial coherence of the light within the cavity to establish a coherent output beam. In this form, the fiber-coupled laser devices may be located in remote sub-groups, thereby reducing the power dissipation density for the external cavity laser.
TL;DR: In this article, the axial mode stability in semiconductor laser is investigated based on the multimode rate equations taking account of transverse mode and carrier density distributions, and a large built-in refractive index step is effective so long as single transverse operation is maintained.
Abstract: Based on the multimode rate equations taking account of transverse mode and carrier density distributions, the axial mode behavior in semiconductor lasers is investigated. The axial mode stability is significantly affected by these distributions. Above threshold, because of hole burning in the carrier density distribution, the gain at any wavelength except the lasing wavelength does not maintain the value at threshold. If the nonlasing mode wavelength is located in the gain decreasing spectral region, its light output decreases with the increase of current. These characteristics are observed in the experiment for a CSP laser. For axial mode stabilization, a large built-in refractive index step is effective so long as single transverse mode operation is maintained. If the injection current region is defined separately from the guiding region, the wider width of the injection current region leads to a more stabilized axial mode.
TL;DR: In this paper, active layer temperature stabilization in semiconductor laser diodes is treated theoretically and numerically, and conditions required for the control circuit are analyzed theoretically and quantitatively.
Abstract: Active layer temperature stabilization in semiconductor lasers is treated theoretically. Laser diodes are assumed to be mounted on a submount which is in contact with a heat sink block. The active layer temperature fluctuation signal is fed back to a Peltier device, an injection current, or a resistor layer in the chip. Active layer temperature stability and conditions required for the control circuit are analyzed theoretically and numerically.
TL;DR: In this article, a simple model system is solved exactly to gain insight on electron-hole interaction effects on the optical properties of semiconductor quantum wells and superlattices, and the transition from three-dimensional behavior (for large $N$) to two-dimensional behaviour (for $N\ensuremath{\sim}1$) is also investigated.
Abstract: A simple model system is solved exactly to gain insight on electron-hole interaction effects on the optical properties of semiconductor quantum wells and superlattices. An $N$-layer film of a simple cubic two-band semiconductor with a contact electron-hole interaction is considered, and the optical absorption function is calculated exactly by Green's-function techniques. The electron-hole interaction introduces peaked structures at subband thresholds in qualitative agreement with experiment. The transition from three-dimensional behavior (for large $N$) to two-dimensional behavior (for $N\ensuremath{\sim}1$) is also investigated.
TL;DR: Asymmetric dependences of the output power on the relative detuning of the resonator arms were observed for different types of semiconductor laser with an external resonator in this paper, and the observed dependences were explained by supplementing the rate equations with a term allowing for the interrelationship between the power, losses, and relative deformation of the resonance arms.
Abstract: Asymmetric dependences of the output power on the relative detuning of the resonator arms were observed for different types of semiconductor laser with an external resonator. The observed dependences were explained by supplementing the rate equations with a term allowing for the interrelationship between the power, losses, and relative detuning of the resonator arms.
TL;DR: In this paper, a series of free-electron laser (FEL) amplifier experiments were conducted at the Los Alamos National Laboratory to measure the energy extraction and the optical gain of "tapered" magnetic wigglers.
Abstract: A series of free-electron laser (FEL) amplifier experiments were conducted at the Los Alamos National Laboratory to measure the energy extraction and the optical gain of "tapered" magnetic wigglers. A 1 ns, 1 GW CO 2 laser pulse, focused at the center of a 1 m long wiggler, will interact with a coaxial, 20 MeV electron beam composed of four 30 ps wide micropulses. Although a single-pass gain of 2 percent is expected, the large difference in pump and electron pulsewidths, plus the inability to fully temporally resolve the 30 ps gain pulses, present special measurement challenges. Therefore, much attention has been given to the enhancement of the size of the gain signal relative to the power of the CO 2 laser pulse. A combination of techniques involving polarization discrimination, signal nulling, and spectral bandwidth discrimination has been determined to be effective. A description of these techniques and their utilization to measure the magnitude and phase of the complex gain G = ge^{i\theta} and the picosecond duration of the gain pulses will be given.
TL;DR: The experimental and theoretical work on free-electron lasers is reviewed in this article, where different amplification schemes and electron scattering mechanisms, the relation between the singleparticle scattering of free electrons in high-energy beams and stimulated scattering by collective oscillations in a dense electron-beam plasma (comparatively low-energy) are discussed.
Abstract: The experimental and theoretical work on free-electron lasers is reviewed. Different amplification schemes and electron scattering mechanisms, the relation between the single-particle scattering of free electrons in high-energy beams and stimulated scattering by collective oscillations in a dense electron-beam plasma (comparatively low-energy) are discussed. Various physical approaches used to describe the processes in freeelectron lasers are discussed. Stimulated multiphoton emission processes in undulators and stimulated Compton scattering processes are examined. The relation between the quantum and classical properties of these phenomena is discussed. The nonlinear behavior of the gain in a free-electron laser under saturation conditions is described. The possibility of optimizing the gain in a Compton laser in a scheme with noncollinear propagation of electrons and electromagnetic waves is discussed.
TL;DR: In this article, an expression for the far field of the TE 0 mode in an asymmetrical dielectric slab waveguide is derived by using normalized waveguide parameters, universal plots of the beamwidth are presented.
Abstract: An expression for the far field of the fundamental TE 0 mode in an asymmetrical dielectric slab waveguide is derived. By using normalized waveguide parameters, universal plots of the beamwidth are presented. These plots include the obliquity factor correction. Experimental results for symmetrical GaInAsP lasers at wavelengths near 1.3 μm are compared with theoretical predictions by Buus and Adams. Calculated results for the 1.55 μm wavelength are presented. A numerical method for the calculation of the far field for structures where four or more layers must be included is outlined.
TL;DR: In this article, the lifetime of GaAlAs V -groove laser was investigated with respect to the lifetime and to the changes in optical properties that are relevant to the operation of these lasers in an optical communication system.
Abstract: The long-term behavior of GaAlAs V -groove lasers has been investigated with respect to the lifetime and to the changes in optical properties that are relevant to the operation of these lasers in an optical communication system. For lasers from two wafers, median lifetimes of 8800 and 11 000 h were obtained at an operation temperature of 70°C. With activation energies of 0.7 and 0.95 eV, median lifetimes between 3.0 \times 10^{5} and 1.3 \times 10^{6} h for room temperature can be extrapolated. The corresponding standard deviations are 1.7 and 0.9, respectively. During the operation of more than 10000 h at 70\deg C , the emission characteristic, the optical spectrum, and the dc signal/noise ratio show only nonessential changes. It should be emphasized that no self-pulsations can be observed even after this long operation time.
Patent•
27 Mar 1981
TL;DR: In this paper, a low-loss optical coupling between an astigmatic semiconductor laser (e.g., gain-guided) and an optical fiber was proposed. But this coupling was not considered in this paper.
Abstract: The invention relates to an optical coupling arrangement, which in particular permits a low-loss optical coupling between an astigmatic semiconductor laser (e.g. a so-called "gain-guided" semiconductor laser) and an optical fibre.
TL;DR: In this article, an e-beam preionized XeCl oscillator has been used to evaluate the performance of acoustic attenuators and contamination due to acoustic absorbing materials.
Abstract: electrode along the opposite wall is separated from the cathode by 2.3 cm. The 1 X 40-cm2 window Of the gun is mounted behind the screen electrode. Through-flow current return paths are provided by arrays of wires up and downstream of the electrodes. The main discharge circuit is of the pulse-charged peaking capacitor design, employing mica capacitors and two parallel Thyratron switches. The circuit stores 13 J at a 38kV charging voltage and produces a 60-nsec discharge voltage rise time and a 20-nsec long discharge current pulse. Experiments have been performed with this system to evaluate the performance of acoustic attenuators and contamination due to acoustic absorbing materials. For this purpose, the original flow which includes a 300-slm tubeaxial fan and a IO-kW finned-tube heat exchanger, was modified to add a vented sidewall muffler downstream of the laser head. Quartz pressure transducers were located in the duct walls up and downstream of the muffler as acoustic diagnostics. Good results have been obtained with resistive walls composed of nickel metal felt over a divided backing volume. The initial discharge pressure pulse is attenuated by a factor of 20 (in pressure). Although the fibrous sidewall material adds 32 m2 of surface area, no significant changes in the outgassing or passivation characteristics of the flow loop are apparent. Operated as an e-beam preionized XeCl oscillator, the device has produced an average power of 58 W at 800 Hz. Reducing the charging voltage delays the onset of downstream arcing, allowing operation at 1 kHz. Experiments to further characterize the high prf performance and to evaluate the effects of acoustic damping will be reported. (Poster paper)