Spontaneous emission behavior in AlGaAs TJS lasers
TL;DR: In this article, spontaneous emission in the direction perpendicular to the lasing direction is experimentally examined in AlGaAs TJS lasers which lase in the fundamental transverse and single longitudinal mode.
Abstract: Spontaneous emission in the direction perpendicular to the lasing direction is experimentally examined in AlGaAs TJS lasers which lase in the fundamental transverse and single longitudinal mode. It is found that the spontaneous emission intensity uniformly saturates above threshold, spatially as well as spectrally. Spontaneous emission peak energy is compared to the lasing energy in a series of lasers with a different Al content in the active region. The energy difference between two energies is shown to be 50 meV and to be independent of the Al content from 0 to 0.26. The absorption coefficient in the active region is calculated from the spontaneous emission spectral shape, which is reasonably explained with the doping condition of the TJS lasers.
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TL;DR: A brief introduction to the AlGaAs single-mode diode laser's characteristics and operation is presented, along with an overview of this laser's contributions to atomic physics research to date as discussed by the authors.
Abstract: Over the past fiie years the use of diode lasers in physics research has expanded rapidly. In part, this has occurred because the diode laser is a highly monochromatic and tunable light source that, when compared to other laser systems, is quite inexpensive and easy to operate. These characteristics make the diode laser ideal for multi-laser experiments, or small scale/high quality research projects in general. In this article a brief introduction to the AlGaAs single-mode diode laser's characteristics and operation is presented, along with an overview of this laser's contributions to atomic physics research to date. It is hoped that this review will facilitate the further use of diode lasers in all aspects of physics, and in particular will aid the small scale researcher in attaining a more active place in mainstream physics.
129 citations
TL;DR: In this paper, the gain saturation characteristics of 1.5 μm InGaAsP traveling-wave laser amplifiers were studied experimentally through the gain saturation characteristics of a weak probe signal, and it was shown that the saturated signal gain spectrum coincides exactly with the unsaturated spectrum under a less biased condition.
Abstract: Spectral line broadening in semiconductor lasers is studied experimentally through the gain saturation characteristics of 1.5 μm InGaAsP traveling‐wave laser amplifiers. Wide signal gain spectrum under the injection of an intense saturating signal is measured using a weak probe signal. The saturated signal gain spectrum is found to coincide exactly with the unsaturated spectrum under a less biased condition, thus verifying that the semiconductor laser gain saturates homogeneously over the entire gain spectrum. Cross‐saturation characteristics between the two signal channels having identical input powers are also investigated and found to be in good agreement with theoretical calculations based on the homogeneous gain model. The degree of gain saturation is confirmed to be uniquely determined by the total output power from both channels.
32 citations
TL;DR: The reliability of 870-900 nm AlGaAs TJS laser has been investigated in this paper, where a nonabsorbing mirror structure is employed to eliminate both gradual degradation and catastrophic damage of the facets.
Abstract: The reliability of 870-900 nm AlGaAs TJS lasers has been investigated An emission wavelength longer than 870 nm is realized by utilizing the band tailing effect due to heavy Zn-diffusion in the active region A nonabsorbing mirror structure is employed to eliminate both gradual degradation and catastrophic damage of the facets Stable continuous operation for over 10 000 hours has been confirmed at ambient temperatures higher than 50°C and output powers more than 5 mW/ facet MTTF longer than 105hours is expected for screened devices Surge endurance has been improved to be nearly one order of magnitude higher than that for a conventional structure
14 citations
TL;DR: In this article, the authors focus on recent advances in the development of a device model which accounts for the qualitative structural and operational differences between lateral and conventional vertical injection lasers and report the results of recent combined theoretical-experimental explorations of laser performance.
Abstract: We review progress in novel semiconductor lasers positioned to enable planar optoelectronic integration and to facilitate the realization of functional photonic devices. Lateral injection of current into the active region of a semiconductor laser has been pursued, mostly empirically, since the early 1970s. In this work, we focus on recent advances in the development of a device model which accounts for the qualitative structural and operational differences between lateral and conventional vertical injection lasers. We review fabrication methods — both established and emerging — suitable for LCI laser realization. Finally, we report the results of recent combined theoretical–experimental explorations of laser performance.
11 citations
TL;DR: In this article, the wavelength characteristics of a transverse junction-stripe AlGaAs laser were precisely measured for a wide range of diode temperatures and injection currents, and a simple rule was found in the mode transition characteristics.
Abstract: The wavelength characteristics of a transverse‐junction‐stripe AlGaAs laser were precisely measured for a wide range of diode temperatures and injection currents. A very simple rule was found in the mode transition characteristics. Typical features of mode competition, such as mode‐competition noise, mode hopping with and without hysteresis phenomenon, and a tristable state of the lasing wavelength, were successively observed for a single diode sample. The characteristics were analyzed theoretically by using a two‐mode intensity equation of laser oscillation under the assumption of a homogeneously broadened gain spectrum. The results were in good agreement with the experiment.
10 citations
References
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IBM1
TL;DR: In this article, the spectral line shapes of the radiation produced by band-to-band recombination of excess carriers in semi-conductors are calculated under the assumption that the momentum matrix element is the same for all initial and final states, i.e., that there is no momentum selection rule.
Abstract: Spectral line shapes of the radiation produced by band-to-band recombination of excess carriers in semi-conductors are calculated under the assumption that the momentum matrix element is the same for all initial and final states, i.e., that there is no momentum selection rule. The peak of the stimulated radiation falls at a lower photon energy than does the peak of the spontaneous radiation, except when $T=0$\ifmmode^\circ\else\textdegree\fi{}K. Some numerical results are given for simple parabolic bands, specifically for the case of electron injection into $p$-type GaAs, and are used to deduce the temperature dependence of the forward current which is necessary to maintain a fixed gain in the active region of a diode. The result is closely related to the temperature dependence of the threshold current in an injection laser, and gives reasonable agreement with experiment. The effect of a conduction band tail is briefly considered.
669 citations
TL;DR: In this article, a model for the calculation of the absorption and emission spectra for GaAs at carrier concentrations in excess of 1×1018 cm−3 is described, which utilizes a Gaussian fit to Halperin-Lax band tails for the concentration-dependent density of states and also includes an energy-dependent matrix element.
Abstract: A model for the calculation of the absorption and emission spectra for GaAs at carrier concentrations in excess of 1×1018 cm−3 is described. This model utilizes a Gaussian fit to Halperin‐Lax band tails for the concentration‐dependent density of states and also includes an energy‐dependent matrix element. The calculated absorption and emission spectra are compared to previous experimental results. All results are for 297 K. For p‐type GaAs, the agreement is very good. The concentration dependence of the effective energy gap is obtained and can be expressed as Eg (eV) =1.424−1.6×10−8 [p (cm−3)]1/3. The concentration‐dependent thermal equilibrium electron‐hole density product n0p0 and the radiative lifetime τr are calculated for p‐type GaAs. The value of n0p0 increases from the low‐concentration value of 3.2×1012 cm−6 to 1.2×1013 cm−6 at p=1.6×1019 cm−3. This value of n0p0, together with the thermal generation rate obtained from the experimental absorption coefficient, gives τr as 0.37 nsec at p=1.6×1019 cm−3.
495 citations
IBM1
TL;DR: In this article, the calculated dependence of the gain coefficient on photon energy and excitation level in GaAs is given for 297 and 77 K. The qualitative behavior of the results is in agreement with experiment.
Abstract: The calculated dependence of the gain coefficient on photon energy and excitation level in GaAs is given for 297 and 77 K. The curves of gain versus excitation rate generally have downward curvature for photon energies near the gain peak, while the envelope of these curves generally has upward curvature except at high excitation rates. Results are also given for the calculated dependence of the radiative recombination rate coefficient and of the photon energy at the gain peak on excitation rate. The qualitative behavior of the results is in agreement with experiment.
283 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
TL;DR: In this paper, the optical wave of wide-stripe lasers is found to be guided by changes in the real part of the dielectric constant that are caused by a dip in carrier concentration along the axis of the lasing filament.
Abstract: Experimental measurements of the optical-beam parameters of conventional oxide-insulated GaAs stripe-geometry lasers as a function of stripe width have shown a marked difference in the waveguide mechanism of narrow-stripe ( \simeq10 \mu m) and wide-stripe ( >20 \mu m) lasers. The optical wave of narrow-stripe lasers is guided by the previously reported gain-guiding mechanism. The optical wave of wide-stripe lasers is found to be guided by changes in the real part of the dielectric constant that are caused by a dip in carrier concentration along the axis of the lasing filament. This self-focused guiding has been predicted theoretically. These experimental results strongly support the hypothesis that in all cases the waveguides are formed predominantly by the naturally occurring variations in carrier concentration beneath the stripe. A new and fairly comprehensive mathematical model has been developed based on this assumption. The model predicts the carrier concentration, resultant gain, and dielectric constant profiles together with the optical-beam parameters and light/current characteristics of stripe-geometry lasers. The model is applicable over a wide range of stripe widths and device structures. The results are compared with experiment over the range of stripe widths from 10-20 \mu m and found in reasonable agreement. The effects of narrowing the stripe width below 10 μm are calculated and found to be in qualitative agreement with recently published experimental results. In particular the light-output power at which a predicted "kink" in the light/current characteristic occurs is found to increase rapidly as the stripe width reduces.
169 citations