Showing papers on "Semiconductor optical gain published in 1980"
TL;DR: In this paper, the authors proposed a method by which 50 kHz resolution can be obtained for measuring the spectrum of stabilised semiconductor laser with high spectral spread, and the principle, experimental set up and results are described.
Abstract: The spectral spread of the best stabilised semiconductor lasers has been reduced to several megahertz. Conventional spectroscopy techniques cannot offer a spectral resolution fine enough for measuring such a sharp spectrum. The letter proposes a novel method by which 50 kHz resolution can be obtained. The principle, experimental set-up and results are described.
917 citations
TL;DR: In this paper, the steplike density-of-states of a quantum-well heterostructure can improve the operation of a semiconductor laser, which is explained in terms of the step-like density of states and the disturbed electron and phonon distributions in the quantumwell active regions.
Abstract: The various features peculiar to the operation of quantum-well semiconductor lasers are described and illustrated with data on single- and multiple-quantum-well Al x Ga 1-x As-GaAs heterostructures grown by metalorganic chemical vapor deposition (MO-CVD). Photo-pumped and p-n diode lasers (injection lasers) are described that are capable of continuous room temperature (CW 300 K) operation. The basic problems of carrier collection, thermalization, and quantum-well band filling are considered and have made clear the limits on single quantum-well laser operation and how these can be overcome with multiple quantum-well active regions. The idea that the steplike density-of-states of a quantum-well heterostructure can improve the operation of a semiconductor laser is shown to be valid. Also, it is shown that phonon participation in the operation of a quantum-well laser, which was not anticipated, is a major (even dominant) effect, with perhaps the phonon emission itself in the compact active region being stimulated. Besides the obvious freedom that quantum-well layers offer in how the active region of a semiconductor laser can be designed, quantum-well lasers are shown to exhibit a lesser sensitivity of the threshold current density on temperature, which is explained in terms of the step-like density-of-states and the disturbed electron and phonon distributions in the quantum-well active regions. Values as high as \sim437\deg C have been obtained for T 0 in the usual expression J_{th}(T) = J_{th}(0) \exp (T/T_{0}) . Since photopumped multiple-quantum-well MO-CVD Al x Ga 1-x As-GaAs heterostructures have operated as CW 300 K lasers with only 5-10 mW of photoexcitation (uncorrected for focusing and window losses, \lambda \sim 5145 A), it is suggested that quantum-well laser diodes can be made that will operate at ∼1 mA or even less excitation.
487 citations
TL;DR: In this article, a new method for measuring absorption and gain spectra of lasers is presented, which is based on the application of general relations between the rates of spontaneous emission, stimulated emission, and optical absorption.
Abstract: A new method for measuring absorption and gain spectra of lasers is presented. These spectra are deduced from measurements of spontaneous emission spectra at different laser currents supplemented by measurements of the laser line energy and the differential quantum efficiency. The spontaneous emission emerged from the side of the laser after traveling through a transparent cladding layer. At each current, the bias energy eV is determined. A simple theoretical model is used to convert eV to minority carrier density. The method is based on the application of general relations between the rates of spontaneous emission, stimulated emission, and optical absorption. A new general proof of these relations is presented. The gain versus carrier density relation at the laser line energy is measured for four samples having different active layer doping or Al composition. Gain increased superlinearly with carrier density in undoped and n‐type samples and increased slightly sublinearly in a p‐type sample. The losses a...
235 citations
180 citations
TL;DR: In this paper, an a.f.c. (automatic frequency control) experiment using a Peltier cooling element is described, where the frequency fluctuation can be reduced to below 10 MHz.
Abstract: In the somewhat distant future, heterodyne-type optical communications will appear, increasing channel capacity and repeater separation. At present, the greatest difficulty is the frequency drift of lasers. The letter describes an a.f.c. (automatic frequency control) experiment using a Peltier cooling element; it is shown that the frequency fluctuation can be reduced to below 10 MHz.
101 citations
Patent•
22 Apr 1980
TL;DR: In this article, an integrated laser array is described in which a plurality of semiconductor lasers are integrated on a semiconductor multi-layer crystal that includes an active layer in which the band gap energy varies in one direction.
Abstract: An integrated laser array is disclosed in which a plurality of semiconductor lasers are integrated on a semiconductor multi-layer crystal that includes an active layer in which the band gap energy varies in one direction By means of this arrangement a plurality of semiconductor lasers, which differ in their respective oscillating wavelengths over a relatively broad range, can be formed on a common substrate
100 citations
TL;DR: In this paper, the small-signal FIR gain coefficients have been measured as functions of the relevant parameters for two transitions in CH 3 OH and three in CH 2 F 2.
Abstract: This study is an investigation of the FIR radiation amplification in CW laser excited gases so essential for a complete quantitative understanding of the FIR laser cycle. The small-signal FIR gain coefficients have been measured as functions of the relevant parameters for two transitions in CH 3 OH and three in CH 2 F 2 . The measurements, demonstrating the influence of coherent pumping have been compared to quantum-mechanical calculations of a three-level system, interacting resonantly with two coherent fields. The good agreement found between theory and measurements indicates the correctness of the theory in predicting the gain properties of the CW FIR lasers. Also FIR gain saturations have been measured directly and exhibit the expected features.
87 citations
TL;DR: In this paper, the optical waveguide, fabrication procedure, major optical properties, and reliability of buried-heterostructure (BH) AlGaAs lasers are described, which are characterized by low threshold currents (10-20 mA), nearly symmetric beam profile, singlemode oscillation, high linearity, small relaxation oscillations, and long-term mode stability.
Abstract: The optical waveguide, fabrication procedure, major optical properties, and reliability of buried-heterostructure (BH) AlGaAs lasers are described. BH lasers are characterized by low threshold currents (10-20 mA), nearly symmetric beam profile, single-mode oscillation, high linearity, small relaxation oscillations, and long-term mode stability. Moreover, BH lasers with a buried optical guide provide CW output powers of 10-20 mW with an overall power conversion efficiency as high as 35 percent.
86 citations
TL;DR: In this paper, the carrier density dependence of the refractive index in the active layers of semiconductor lasers is evaluated from the wavelength shift with increases in current by taking into account effects of the active layer temperature rise and lateral carrier and optical field distributions on the wavelength shifting.
Abstract: Carrier density dependence of the refractive index in the active layers of semiconductor lasers is evaluated from the wavelength shift with increases in current by taking into account effects of the active layer temperature rise and lateral carrier and optical field distributions on the wavelength shift. The derived refractive index change due to carrier density increase is -4 \times 10^{-27} m3, which is in good agreement with the theoretical value.
70 citations
Patent•
25 Jan 1980TL;DR: In this article, a three-dimensional optical waveguide is described, which consists of a single crystal semiconductor layer grown upon an insulator which has an index of refraction lower than the semiconductor.
Abstract: A three-dimensional optical waveguide is disclosed. This waveguide comprises a single crystal semiconductor layer grown upon an insulator which has an index of refraction lower than the semiconductor. The semiconductor layer has a thickness which provides confinement of light propagating in the semiconductor layer in the vertical direction. An effective larger index of refraction over a cross-sectional region of the semiconductor layer provides confinement of light in the lateral direction. This lateral confinement is achieved by side walls in the semiconductor layer which extend toward, but fall short of, the insulator layer.
59 citations
TL;DR: The upper limit of the achievable signal-to-noise ratio in optical communication systems is determined by the intrinsic laser noise due to quantum fluctuations inside the laser cavity as discussed by the authors, and it is concluded from theoretical calculations and from measurements on V-groove lasers that a d.c.
Abstract: The upper limit of the achievable signal-to-noise ratio in optical communication systems is determined by the intrinsic laser noise due to quantum fluctuations inside the laser cavity. This achievable signal-to-noise ratio depends on the way in which different lasing modes are detected; wavelength filtering and material dispersion may yield a significant deterioration of the signal-to-noise ratio. It is concluded from theoretical calculations and from measurements on V-groove lasers that a d.c. signal-to-noise ratio of about 70 dB may be achieved for a noise bandwidth of 10 MHz.
TL;DR: In this paper, the authors show that the mode selection mechanism is due to the spatial variation in the optical loss created by the standing-wave pattern of the single predominant mode, which results in a lower average loss for the creating mode and a higher loss for all other modes.
Abstract: Recently it has been observed that certain single-transverse-mode semiconductor lasers continue to emit light predominantly in a particular longitudinal mode even after the optical gain peak has shifted by one or more mode spacings due to changes in bias current or temperature [1], [2]. The purpose of this paper is to show that this type of mode stabilization can be caused by the saturable optical absorption resulting from deep-level states or traps, which have been observed in AlGaAs laser structures [3]-[7]. The mode-selection mechanism is due to the spatial variation in the optical loss created by the standing-wave pattern of the single predominant mode. This loss pattern results in a lower average loss for the creating mode and a higher loss for all other modes. It is possible that laser devices with greatly improved single-mode stability can be made by introducing traps of the proper type and density during fabrication.
TL;DR: In this article, the authors measured the gain of an AlGaAs laser amplifier with an optical isolator and reported that the maximum net gain was 25 dB when input power was less than 40 dBm.
Abstract: Results of gain measurements on an AlGaAs laser amplifier with an optical isolator are reported. The maximum net gain was 25 dB when input power was less than ?40 dBm. By measuring internal loss, a saturation parameter was estimated to be 6 mW.
TL;DR: In this paper, a simple model for a semiconductor diode laser in an external cavity is developed, and the stability and small-signal modulation characteristics of the new model are investigated and compared with experiment.
Abstract: A simple model for a semiconductor diode laser in an external cavity is developed. The stability and small-signal modulation characteristics of the new model is investigated and compared with experiment.
TL;DR: A simple configuration made of a conventional AlGaAs diode laser without antireflection coating combined with an external reflector and an optical etalon was proved to be practically feasible to generate bandwidth limited mode-locked optical pulses of 30 ps duration by synchronous modulation at the external cavity mode interval.
Abstract: A simple configuration made of a conventional AlGaAs diode laser without antireflection coating combined with an external reflector and an optical etalon was proved to be practically feasible to generate bandwidth limited mode-locked optical pulses of 30 ps duration by synchronous modulation at the external cavity mode interval. Generated optical pulse shape was found to be Lorentzian rather than Gaussian for the first time, based on the measurements of both the s.h.g. correlation method and the ultrafast streak camera.
TL;DR: In this article, the authors provide basic physical information on the photodissociation of metal halides, and a study of the laser physics of these devices provides basic physical and theoretical information.
Abstract: UV photodissociation of alkali and group IIIa metal halides provides a simple, practical means of producing metal-atom resonance-line lasers. These lasers are useful for applications in remote sensing of the same metal atoms. A study of the laser physics of these devices provides basic physical information on the photodissociation of metal halides.
TL;DR: Numerical solutions show that optical gain can be deduced only for a limited regime of experimental parameters and theoretical analysis is examined with experimental gain data for organic dyes in the vapor phase and in liquid solution.
Abstract: Laser gain determination by means of amplified spontaneous emission is discussed in terms of a rate-equation approach Numerical solutions show that optical gain can be deduced only for a limited regime of experimental parameters The theoretical analysis is examined with experimental gain data for organic dyes in the vapor phase and in liquid solution In addition, the gain of electron-beam-excited Ar–N2 and XeF laser mixtures has been studied
TL;DR: In this article, the authors investigated the dependence of the pulsation characteristics on the external cavity length using a saturable absorber model for self-pulsing and non-Pulsing lasers coupled to external cavities.
Abstract: The behavior of self-pulsing and nonpulsing lasers coupled to external cavities is investigated experimentally and theoretically. We investigate the dependence of the pulsation characteristics on the external cavity length using a saturable absorber model for self-pulsing lasers. It was found that quenching of self-pulsation occurs only for a certain limited range of external cavity length, and the frequencies of external-cavity induced pulsations lies within a certain range determined by the coupling coefficient. Small-signal analysis allows these ranges to be derived analytically. Hitherto, complex pulsation phenomena can be explained very intuitively by interpreting the combined laser-external cavity system as a microwave oscillator with a limited gain band and discrete mode structure.
Patent•
16 May 1980TL;DR: In this article, a stripe geometry is fabricated in a laser-diode structure having a plurality of epitaxial layers, including in tandem an undoped active semiconductor layer (3), a p-doped semiconductor layers (4), a moderately n-drone semiconductor (5) and a heavily p + -doped layer (6).
Abstract: A stripe geometry is fabricated in a laser-diode structure having a plurality of epitaxial layers, including in tandem an undoped active semiconductor layer (3), a p-doped semiconductor layer (4), a moderately n-doped semiconductor layer (5) and a heavily p + -doped layer (6) by focusing laser radiation on the n-doped semiconductor layer (5). The laser radiation is chosen to have a wavelength which passes through the p + -doped layer (6) without absorption. When the laser radiation is absorbed in the n-doped layer, heat is generated which causes diffusion of p-dopant from the two adjacent layers to convert the exposed region to p-type. As the laser beam is scanned, a stripe having a forward pn junction for laser action is formed.
TL;DR: In this paper, the laser-emission of ZnO- and CdS-crystals is measured as a function of temperature under two-excitation, and the laser thresholds are determined and compared with theoretical calcualtions.
TL;DR: A simple linearizing technique for improving the nonlinearity of laser diodes, using an emphasis principle, is proposed and was experimentally examined, yielding promising results.
Abstract: Experimental investigation was carried out on nonlinear video distortions of differential gain and differential phase in various optical transmitters using laser diode structures having a single transverse mode operation. It was observed that the measured nonlinearity of laser diodes was comparable to that of a typical LED. A simple linearizing technique for improving the nonlinearity, using an emphasis principle, is proposed and was experimentally examined, yielding promising results.
Patent•
17 Jun 1980TL;DR: In this article, a body of semiconductor material is biased with multi-kilovolt voltage to establish an electric field approaching the dielectric breakdown field for the semiconductor materials.
Abstract: A body of semiconductor material is biased with multi-kilovolt voltage to establish an electric field approaching the dielectric breakdown field for the semiconductor material. Low level optical energy, such as a laser pulse in the nano-joule range produces free carriers in the semiconductor which multiply in the presence of the electric field to produce avalanche conduction through the semiconductor body thereby switching the multi-kilovolt voltage in precise timed (picosecond) relationship with the application of the optical energy and with high switching or turn on sensitivity.
TL;DR: In this article, an aging process occurs during lasing operation which has the effect of partially annealing the proton induced carrier removal concentration at the edges of the active stripe of the laser.
Abstract: Experimental observations indicate that the occurrence of optical self-pulsation in proton delineated stripe-geometry double-heterostructure junction lasers is related to the degree of gain guiding inherent in individual lasers. We show that an aging process occurs during lasing operation which has the effect of partially annealing the proton induced carrier removal concentration at the edges of the active stripe of the laser. In some lasers, the magnitude of this annealing effect is sufficiently large to flatten the active stripe carrier concentration profile thus reducing filament stability leading ultimately to optical self-pulsation. It is shown that the carrier concentration profile modification is due to the dual effects of decreasing the n = 2 nonradiative current component at the active stripe-proton bombarded interface as well as the geometric effect of increasing the laser active stripe width. This latter effect may be also responsible for some portion of laser threshold current increase observed during device operation.
TL;DR: In this article, a simple lightwave pulse regenerator has been built by adding a photodiode with less than unity gain, which can emit lightwave pulses with 6 pJ energy, less than 0.2 ns in duration, and with an amplitude that is up to 15 times larger than the input pulse.
Abstract: A triggerable semiconductor laser emits light in very short (0.1 ns) intense (0.1 W) pulses with a few nanosecond periods when biased a fraction of a milliampere above a threshold current. Single uniform lightwave pulses can be triggered by fractional milliampere current pulses up to several nanoseconds in duration. This behavior was first seen in computer simulations of devices with a high electron-trap density (other causes are possible). Devices exhibiting this behavior have been found among the population of AlGaAs stripe lasers made by deep proton bombardment. A simple lightwave pulse regenerator has been built by adding a photodiode with less than unity gain. This circuit emits lightwave pulses with 6 pJ energy, less than 0.2 ns in duration, and with an amplitude that is up to 15 times larger than the input pulse.
TL;DR: In this paper, the authors measured the near field intensity distributions of three lead-sulfide-selenide diode diode lasers operating near 4.8 μm as a function of injection current.
Abstract: Measurements of the near-field intensity distributions of three lead-sulfide-selenide diode lasers operating near 4.8 μm have been made as a function of injection current. Localized emission in the near field exhibits peaked structure of full width from 5 to 10 μm for operation above threshold. From the dependence of the emission profiles on injection current estimates of 25 cm-1and 0.09 cm/A are made for the distributed loss and gain coefficients for one of the lasers. Optical confinement perpendicular to the p-n junction can be explained in terms of the homojunction properties.
TL;DR: In this article, the nature of the output intensity fluctuation noise generated when semiconductor lasers are irradiated by their own output beam is described and a possible explanation of their generation mechanism is presented utilising a simple rate equation model with an additional term accounting for the multiple reflections of the laser beam.
Abstract: The nature of the output intensity fluctuation noise generated when semiconductor lasers are irradiated by their own output beam are described. A possible explanation of their generation mechanism is presented utilising a simple rate equation model with an additional term accounting for the multiple reflections of the laser beam.
TL;DR: In this paper, a wavelength detector suitable for use with semiconductor laser packages has provided control of laser emission wavelengths to better than 0.1 A. Special features of the detector have also enabled mode hopping, gain profile shift and end of single mode lifetimes to be observed.
Abstract: A wavelength detector suitable for use with semiconductor laser packages has provided control of laser emission wavelengths to better than 0.1 A. Special features of the detector have also enabled mode hopping, gain profile shift and end of single-mode lifetimes to be observed.
TL;DR: In this article, the rotation of the plane of polarization of the return beam perpendicular to that of the outgoing laser beam using a quarterwave plate in the self-coupled use of a semiconductor laser diode effectively suppresses the operation instability which degrade S/N performance in optical memory playback applications.
Patent•
25 Aug 1980TL;DR: A semiconductor injection laser is provided with an integrated optical injector means on same substrate as the laser which has an optical emitter region noncolinear with the axis of optical emission from the laser but optically coupled to the laser at one or more points along its length as discussed by the authors.
Abstract: A semiconductor injection laser is provided with an integrated optical injector means on same substrate as the laser which has an optical emitter region noncolinear with the axis of optical emission from the laser but optically coupled to the laser at one or more points along its length. The optical injector means is independently operative prior to or simultaneously with the independently operated laser to inject radiation into the laser optical emitter region to decrease the response time of the laser to pulsed current modulation.
TL;DR: In this article, a field effect semiconductor (FES) laser is proposed, in which the both sides of the active region are surrounded by the burying layers with the reverse-biased p-n junctions.
Abstract: A new semiconductor laser, the field-effect semiconductor (FES) laser, in which the both sides of the active region are surrounded by the burying layers with the reverse-biased p-n junctions is proposed. The proposed FES laser is a Q -switching device based on the direct control of laser beam intensity by the internal loss modulation through the field effect. The structure design and the operating principles of the device are discussed. Numerical solution shows that a pulsewidth shorter than 30 ps can be obtained.