GaAs Junction Lasers Research Articles

Influence of uniaxial pressure on the critical temperature for long delays in GaAs junction lasers

In this work we report on the influence of uniaxial pressure applied perpendicularly to junction laser on the behavior of the critical temperature for the onset of long delays in GaAs junction lasers. Experimental data showing this influence for lasers operating in a TE or TM polarization are presented and explained on the basis of a thermal theory of long delays and related phenomena.

Transient effects in single heterostructure GaAs lasers

We apply our theory on long delays in GaAs junction lasers to describe the transient phenomena of SH GaAs lasers. This is done at the beginning of the exciting pulse and at the instant of lasing either with a long delay or with <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</tex> -switching. The abrupt reduction of spontaneous emission at the instance of lasing with a long delay is shown to occur as a consequence of a reduction in the carrier density that takes place during the transient period. It is also shown that <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</tex> -pulsing can occur only in a very special case.

Theory of spontaneous emission reduction at lasing with long delays in GaAs junction lasers

In this work it is shown that the large abrupt reduction of the spontaneous emission of a single heterostructure laser that lases with a long delay, can be explained with the dynamic behavior of the diffraction losses during the current pulse. In our calculations the diffraction losses are governed by the perturbation of refractive index of the laser active region caused by the injected carriers, Joule heating and gain guiding.

Spectral hole burning in GaAs junction lasers

Spectral hole burning corresponding to a gain reduction of the order of 1% has been observed in GaAs junction lasers. This observation is made possible by the use of the strong superradiant amplification of the spontaneous emission along the junction.

A theory on long time delays and internal Q switching in GaAs junction lasers

In this paper we present a theory that explains long time delays and internal Q switching in GaAs junction lasers, using only processes known to occur in these lasers: perturbation of refractive index of the active region by injected carriers, joule heating, and gain guiding.

Theory on long time delays, Q -switching and related phenomena in GaAs junction lasers

We present a theory that explains long time delays. Q-switching and related phenomena in GaAs junction lasers, based only on processes known to occur in these lasers.

Distributed-Feedback Double-Heterostructure GaAs Injection Laser with Fundamental Grating

The pulse operation of two DEF GaAs junction lasers employing the fundamental grating order at 77$sup 0$K for double-heterostructures formed by both liquid and vapor phase epitaxy is described. (TFD)

Reflectivity dependence of the lasing photon energy in GaAs junction lasers at 77°K

The reflectivity dependence, of the lasing photon energy in GaAs junction lasers at 77° K is studied. It is found that the lasing photon energy decreases with increasing values of the laser reflectivity.

Microlenses for Coupling Junction Lasers to Optical Fibers

Microscopic lenses, fabricated on optical fiber surfaces, have quadrupled the efficiency for coupling astigmatic beams from GaAs junction lasers into 4-microm cores of single-mode fibers. A novel photolithographic technique was used to make hemispherical and hemicylindrical microlenses, with diameters between 4 microm and 10 microm, from commercially available negative type photoresist that is transparent at ir laser wavelengths. Geometrical profiles of photoresist lenses, documented with scanning electron photomicrographs, were remarkably smooth even though their dimensions were more than an order of magnitude smaller than other known lenses.

Advances in GaAs junction lasers with stripe geometry

Abstract A review of the properties of stripe geometry GaAs junction lasers is presented. Some of the topics discussed are: filaments, fabrication techniques, thermal design for continuous operation, modes and spontaneous pulsing.

Behavior of spontaneous emission across threshold in GaAs junction lasers

The spontaneous emission behavior of a cw stripe-geometry GaAs laser is examined in detail. Contrary to recently published results, a sharp discontinuity of the spontaneous emission growth occurs when the laser reaches threshold. Above threshold, slow increases in the spontaneous emission are observed, coming mostly from the regions where the lasing light intensity is small. Other discontinuity points were, at higher currents, observed corresponding to the onset of higher-order modes and second-order mode locking.

Conservation of Polarization in GaAs Junction LASER

Conservation of Polarization in GaAs Junction LASER

Second-order dispersion in oscillating GaAs junction lasers

The frequency separation between adjacent longitudinal modes in semiconductor lasers varies from mode to mode over the laser spectrum because of the effects of dispersion in the laser medium. Because of the interest in mode locking and self-pulsing of GaAs lasers it is desirable to know the magnitude of this effect. We have measured this variation of mode separation by measuring the correlation function of the field amplitude in the output beam of an oscillating, diffused junction, stripe geometry GaAs laser operating CW at \sim80\deg K. The correlation function is measured with a Michelson interferometer and is facilitated by using a diode that simultaneously oscillates in two widely separated families of longitudinal modes. The significance of this measurement to mode locking and self-pulsing in GaAs lasers is discussed.

Mode configurations in second-order mode-locked lasers

An analysis of the mode frequencies and phases of lasers that are self-pulsing due to second-order mode locking is presented. It is shown that locking can occur with the modes arranged in several different configurations with different pulsing frequencies corresponding to the beat notes between different combinations of longitudinal modes. The experimental observations of the transition between two of these configurations in a self-pulsing GaAs junction laser is reported.

A proposed method for determining the characteristic energies of exponential band tails in GaAs junction lasers †

Abstract Ths wavelength shift with cavity Q in GaAs junction lasers with exponential band tails as experimentally observed eleswhere is related to the characteristic energies of the distribution of the tail states in both the conduction and valence bandfl. A method is then proposed for determining the band-tailing parameters in GaAs junction lasers from measurements of the wavelength shift with cavity Q and the linewidth of spontaneous emission preceding laser action. The accuracy of the method will be fairly high since the measurements on which the method is based could be done precisely and also since the assumptions involved in the method are quite valid under most of the practical situations.

Time dependence of the shift of the energy of peak emission in GaAs junction lasers operated with a flat-topped current pulse at 77°K

The shift of the energy of peak emission resulting from rise of the junction temperature in GaAs junction lasers during operation with a flat-topped current pulse is studied theoretically as a. function of time. The nature of this dependence is found to be in qualitative agreement with the experimental observation of such a dependence in GaAs 1-x P x junction losers as reported elsewhere. The effects of increasing doping and increasing amplitude of the current pulse on the time dependence of the energy shift are also studied. In addition expressions are derived for the maximum time duration of the output light pulse that can be obtained under the limitations of junction heating and the maximum possible shift in the energy of peak emission that may occur as a consequence of such heating.

Reflectivity dependence of the junction temperature rise and the stimulated light power in GaAs junction lasers operated continuously at 77° K

The reflectivity dependence of the junction temperature rise, the total stimulated light power and the power efficiency in solution-grown GaAs junction lasers operated continuously at 77° K is studied. It is found that both the stimulated light output and the power efficiency can be maximised at a given current density by changing the laser reflectivity. It is also concluded that even when the laser diode is capable of with-standing a considerable rise in the junction temperature, the operation of the diode with a large biasing current above a certain level may prove not to be useful, as the junction heating will ultimately limit the stimulated light power.

STRIPE-GEOMETRY DOUBLE HETEROSTRUCTURE JUNCTION LASERS: MODE STRUCTURE AND cw OPERATION ABOVE ROOM TEMPERATURE

Double heterostructure GaAs junction lasers have been operated continuously at temperatures up to 355°K by use of the advantageous thermal properties of the stripe-geometry configuration. Spatial and spectral characteristics of the modes of these lasers are reported. For the direction perpendicular to the junction plane, these observations show that the field distributions are more symmetrical, the focusing is stronger, and operation in high-order modes is more easily achieved than in homostructure (diffused) junction lasers. For the direction along the junction plane, no significant differences are found between double heterostructure and homostructure lasers.

A proposed method for determining the thickness of the active region in GaAs junction lasers

A method is shown for determining the thickness of the active region in GaAs junction lasers from measurements of the mobility and lifetime of the minority carriers and the linewidth of spontaneous emission preceding laser action. The accuracy of the method will be fairly high since the measurements on which the method is based could be done precisely by techniques known in the literature.

Excitation and Doping Dependences of Electron Diffusion Length in GaAs Junction Lasers

The dependence of electron diffusion length on the excitation and impurity compensation in the p region of a GaAs junction laser has been calculated from the band theory of impure semiconductors. Using a screened potential for each impurity atom, the average room-temperature diffusion length in a typical diffused diode is found to be 1.4 μ at low injection limit. The diffusion length increases with increase in excitation because of the enhancement in carrier screening and carrier diffusion energy. This effect can be used to explain the much lower threshold current in an AlxGa1−xAs–GaAs heterostructure laser and an abnormally high threshold current in a shallow diffused homostructure laser. Furthermore, the electron diffusion length is found to be larger for the region near the junction due to longer electron lifetime in this region. This also explains the observation that in a normal diffused junction laser, the active region occurs somewhere in the p region but not right next to the space-charge region.