Showing papers on "Semiconductor optical gain published in 1974"
TL;DR: In this article, the electron states of an indirect optical semiconductor with two bands were calculated in the presence of an additional periodic one-dimensional potential (superlattice) in the semiconductor material.
Abstract: Starting from a model of an indirect optical semiconductor with two bands, the electron states are calculated in the presence of an additional periodic one-dimensional potential (superlattice) in the semiconductor material. These states are used to determine the transition probability connected with the absorption of a photon. This transition corresponds to an optical direct transition — no phonon takes part in this process. The optical direct and optical indirect transitions are compared. For optical frequencies near the band gap one expects only direct transitions, whereby the optical indirect transitions may be neglected.
207 citations
TL;DR: In a suitably designed semiconductor laser, spontaneously emitted photons with energies above the absorption edge can be reabsorbed in the active layer and can decrease the current density that must be supplied to reach the lasing threshold as mentioned in this paper.
Abstract: In a suitably designed semiconductor laser, spontaneously emitted photons with energies above the absorption edge can be reabsorbed in the active layer and can decrease the current density that must be supplied to reach the lasing threshold. The magnitude of the threshold reduction is estimated to be about 20% in a GaAs double‐heterostructure laser at room temperature.
102 citations
TL;DR: In this article, the concept of mode stability is considered in detail and a procedure is developed for determining the stability of laser resonators and optical waveguides containing arbitrary lens elements.
Abstract: The concept of mode stability is considered in detail and a procedure is developed for determining the stability of laser resonators and optical waveguides containing arbitrary lens elements. It is found that under some conditions the addition of a laser medium with a gain profile makes oscillation or propagation impossible in an otherwise stable system. A new formalism is described for the propagation of off-axis modes.
58 citations
TL;DR: In this paper, the coupling between GaAs injection lasers and multimode optical fibers using spherical ends on the optical fibers is examined, and the results previously published by Kato are shown to be overly optimistic, although considerable improvement over using a flat-ended fiber is still predicted.
Abstract: The coupling between GaAs injection lasers and multimode optical fibers using spherical ends on the optical fibers is examined. In particular, the results previously published by Kato are shown to be overly optimistic, although considerable improvement over using a flat‐ended fiber is still predicted. Neglecting reflection losses, we predict maximum coupling efficiencies of the order of 60–70% for our typical double‐heterostructure laser diodes and have experimentally measured 62% in a case for which 60% is expected from the theory.
30 citations
TL;DR: A critical review is made of the available experimental data and the proposed theoretical explanations regarding long delays and Q switching in semiconductor lasers and shows that no model is completely satisfactory in explaining all the available data.
Abstract: A critical review is made of the available experimental data and the proposed theoretical explanations regarding long delays and Q switching in semiconductor lasers. It is shown that no model is completely satisfactory in explaining all the available data. Guidelines for developing a better theory are presented.
25 citations
TL;DR: In this article, stress birefringence in optically pumped laser rods and spherical aberration due to heating of intracavity elements, such as a nonlinear crystal, by the laser beam are discussed.
Abstract: Heating of intracavity solid-state materials causes isotropic and anisotropic variations in the index of refraction which lead to optical phase and amplitude distortions of the oscillating mode. Two important perturbations are discussed: stress birefringence in optically pumped laser rods and spherical aberration due to heating of intracavity elements, such as a nonlinear crystal, by the laser beam. While these perturbations are well determined, their effect on optical resonators cannot be inferred from the single-pass data in any simple way.
20 citations
01 Nov 1974
TL;DR: In this paper, the light output powers of a semiconductor laser diode within an external cavity and of two optical coupled diodes are evaluated as a function of the system parameters (drive currents and coupling coefficient).
Abstract: The light output powers of a semiconductor laser diode within an external cavity and of two optical coupled diodes are evaluated as a function of the system parameters (drive currents and coupling coefficient). The calculations are based on a rate equation approach. A power law dependence between optical gain and electron density has been assumed and spontaneous emission into the amplified light field is taken into account in this approach. Analytical approximations are evaluated for the photon number within the diode cavity. With the exception of a small region near threshold there is good agreement between approximations and numerically calculated photon numbers. The theoretical results are compared with experimental data and good quantitative agreement is found in both cases, the diode in the external cavity and the optical coupled diodes.
17 citations
TL;DR: In this paper, the degradation of double heterostructure diode laser with stripe structure has been investigated and it was found that the degradation was caused by local crystalline defects produced by internal stresses and local weakness.
Abstract: Semiconductor lasers, first demonstrated in 1962, have spent a long time in development without finding many applications. (GaAl)As double heterostructure diode lasers with stripe structure have distinctive characteristics for cw operation with a pure mode, in addition to their compactness and ease of operation. Quick degradation of these lasers has been investigated and it was found that the degradation was caused by local crystalline defects produced by internal stresses and local weakness. Improvements based on the study have provided reliable lasers with an operating life of over several thousand hours. These new generation lasers will be useful for optical communications and other optical systems.
14 citations
TL;DR: Gain formulas for the 10.4 and 9.4-μm CO 2 bands for the high-pressure broadening case were shown in this paper, and the results showed that continuously tunable lasers over the entire 9.6 and 10.1-μM bands with no rotational structure were possible.
Abstract: Gain formulas are shown for the 10.4- and 9.4-μm CO 2 bands for the high-pressure broadening case to point out a new regime of operation for this laser. Computer-simulated results of this gain are presented as a function of wavenumber, with density equivalent pressure and population inversion ratio as parameters. The results show gain curves that suggest continuously tunable lasers over the entire 9.4- and 10.4-μm bands with no rotational structure.
13 citations
TL;DR: In this paper, a method for the fabrication of GaAs semiconductor lasers with an emission region several microns wide was described and the results of an investigation of the radiative characteristics of such lasers were given.
Abstract: A description is given of a method for the fabrication of GaAs semiconductor lasers with an emission region several microns wide The results are given of an investigation of the radiative characteristics of such lasers It is reported that the emission is of the single-mode type when the threshold is exceeded by a factor of 3–4
10 citations
Patent•
11 Oct 1974
TL;DR: In this article, a luminosity control device comprises a first semiconductor laser operable in a spontaneous mode to emit non-coherent light and in a laser mode different from its inherent laser modes to emit coherent light.
Abstract: A luminosity control device comprises a first semiconductor laser operable in a spontaneous mode to emit noncoherent light and in a laser mode different from its inherent laser mode to emit coherent light. The first semiconductor laser is electrically biased into its spontaneous laser mode. A second semiconductor laser is operated in a laser mode to emit coherent light which is applied to the first semiconductor laser to optically bias the first semiconductor laser into the laser mode of the second semiconductor laser. The second semiconductor laser is electrically biased into operating in its laser mode and the optical coupling between the two semiconductor lasers is such that the coherent light output from the first semiconductor laser varies exponentially with respect to the electrical energy input into the second semiconductor laser.
TL;DR: In this article, the theory of optical gain in highly doped semiconductors employed for semiconductor lasers is developed based on the Green function approach, with the help of the analytical expression obtained for optical gain, the threshold properties of semiconductor laser and their dependence on concentration of doping impurities and on temperature are studied.
Abstract: The theory of optical gain in highly doped semiconductors employed for semiconductor lasers is developed based on the Green function approach. With the help of the analytical expression obtained for optical gain, the threshold properties of semiconductor lasers and their dependence on concentration of doping impurities and on temperature are studied. Results of numerical calculations of threshold characteristics for the most interesting cases are presented.
NEC1
TL;DR: In this article, an improved treatment of the intraband relaxation in the analysis of the saturation behavior of the optical gain in semiconductor lasers has been proposed to eliminate the spectral hole-burning effect.
Abstract: A recent analysis of the saturation behavior of the optical gain in semiconductor lasers has predicted a strong spectral hole-burning effect. With an improved treatment of the intraband relaxation in the analysis the effect disappears entirely.
Patent•
09 Aug 1974TL;DR: In this article, an optical device for gating an incident light ray which utilizes the principle of absorption edge shift in a semiconductor due to an external electric field was proposed, in which a PN junction was provided for control purposes such that the potential is primarily dropped across the junction.
Abstract: An optical device for gating an incident light ray which utilizes the principle of absorption edge shift in a semiconductor due to an external electric field. The optical device comprises a semiconductor material and a source of bias potential applied thereacross. In a preferred embodiment, a PN junction is provided for control purposes such that the potential is primarily dropped across the junction. The absorption band edge of the semiconductor is selected to correspond to the wavelength of the incident radiation to be controlled whereby in the normal mode of operation, the semiconductor appears to be transparent to the incident radiation. When charged carriers are introduced at the junction, the potential is dropped across the semiconductor, causing an absorption edge shift towards longer wavelengths. In this mode of operation, the incident radiation is substantially absorbed, or attenuated, by the semiconductor.
TL;DR: In this paper, an approximate analysis for calculating the reflection and transmission coefficients at the junction discontinuity between two planar dielectric waveguides when there is a gap between them is presented.
Abstract: In the letter, an approximate analysis is developed for calculating the reflection and transmission coefficients at the junction discontinuity between two planar dielectric waveguides when there is a dielectric gap between them. The analysis is applied to the junction between a heterojunction laser and a planar optical waveguide with an airgap, and results are presented showing the variation of the reflection and transmission coefficients with the gapwidth.
TL;DR: In this paper, an injection laser was used to study the spectral characteristics of the selective reflection from Cs133 vapor in the pressure range 0.5-130 mm Hg, and an analysis was made of the possibility of using this reflection in the stabilization of a semiconductor laser at the frequency of an atomic resonance line.
Abstract: An injection laser was used to study the spectral characteristics of the selective reflection from Cs133 vapor in the pressure range 0.5–130 mm Hg. An analysis was made of the possibility of using this reflection in the stabilization of the frequency of a semiconductor laser at the frequency of an atomic resonance line.
TL;DR: In this paper, the emission patterns of single heterostructure lasers have been calculated as a function of the refractive index step between the p GaAs active region and the n GaAs substrate.
Abstract: The emission patterns of single heterostructure lasers have been calculated as a function of the refractive-index Step between the p GaAs active region and the n GaAs substrate. The conclusions that higher n doping levels should produce better optical confinement and a wider far-field pattern are supported by experimental measurements, from which the refractive index can be deduced.
TL;DR: In this paper, an analysis of nonstationary excitation of many oscillation modes in a semiconductor laser whose emission is subject to intensity pulsations (spikes) is made.
Abstract: An analysis is made of nonstationary excitation of many oscillation modes in a semiconductor laser whose emission is subject to intensity pulsations (spikes). It is shown that even near the laser threshold the average emission spectrum consists of many modes if the pulsations of the intensity are sufficiently deep. An expression is derived for the width of the emission spectrum and its dependence on the pumping power.
TL;DR: In this paper, the small-signal gain and time-resolved spectral output of a flash-initiated D 2 -F 2 /CO 2 chemical transfer laser system are reported.
Abstract: Measurements made of the small-signal gain and time-resolved spectral output of a flash-initiated D 2 -F 2 /CO 2 chemical transfer laser system are reported. Small-signal gain measurements indicate a possible lack of rotational equilibration among the rotational levels of the CO 2 during the DF-CO 2 V-V energy transfer process. Time-resolved spectral output of this system, operated as a laser oscillator, is presented as verification of the small-signal gain results.
TL;DR: In this article, the laser gain associated with interband transitions in heavily doped semiconductors was investigated and analytical expressions for the gain and quasi-Fermi levels were derived as a function of impurity concentration, temperature, and pumping power.
Abstract: A theoretical, investigation is made of the laser gain associated with interband transitions in heavily doped semiconductors. Analytic expressions are obtained for the gain and quasi-Fermi levels considered as a function of the impurity concentration, temperature, and pumping power.
TL;DR: In this paper, a new multimode mechanism of the stimulated emission from a semiconductor laser is considered, where the excitation of several axial modes in the presence of intensity pulsations is attributed to the compensating influence of the spontaneous emission on the effective gain of the secondary modes, which are neighbors of the dominant mode excited at the threshold.
Abstract: A new multimode mechanism of the stimulated emission from a semiconductor laser is considered. The excitation of several axial modes in the presence of intensity pulsations is attributed to the compensating influence of the spontaneous emission on the effective gain of the secondary modes, which are neighbors of the dominant mode excited at the threshold. The intensities of these secondary modes increase when the depth of modulation of the output radiation is increased. This mechanism explains the multimode stimulated emission near the self-excitation threshold of semiconductor lasers.