Simulation of high brightness tapered lasers

Tapered semiconductor lasers have demonstrated both high power and good beam quality, and are of primary interest for those applications demanding high brightness optical sources. The complex non-linear interaction between the optical field and the active material requires accurate numerical simulations to improve the device design and to understand the underlying physics. In this work we present results on the design and simulation of tapered lasers by means of a Quasi- 3D steady-state single-frequency model. The results are compared with experiments on Al-free active region devices emitting at 1060 nm. The performance of devices based on symmetric and asymmetric epitaxial designs is compared and the influence of the design on the beam properties is analyzed. The role of thermal effects on the beam properties is experimentally characterized and analyzed by means of the numerical simulations. Tapered lasers with separate electrical contacts in the straight and tapered sections, based on symmetrical and asymmetrical epitaxial designs are also presented and analyze

Simulation of facet heating in high-power red lasers

A two-dimensional self-consistent laser model has been used for the simulation of the facet heating of red emitting AlGaInP lasers. It solves in the steady-state the complete semiconductor optoelectronic and thermal equations in the epitaxial and longitudinal directions and takes into account the population of different conduction band valleys. The model considers the possibility of two independent mechanisms contributing to the facet heating: recombination at surface traps and optical absorption at the facet. The simulation parameters have been calibrated by comparison with measurements of the temperature dependence of the threshold current and slope efficiency of broad-area lasers. Facet temperature has been measured by micro-Raman spectrometry in devices with standard and non absorbing mirrors evidencing an effective decrease of the facet heating due to the non absorbing mirrors. A good agreement between experimental values and calculations is obtained for both devices when a certain amount of surface traps and optical absorption is assumed. A simulation analysis of the effect of non absorbing mirrors in the reduction of facet heating in terms of temperature, carrier density, material gain and Shockly-Read-Hall recombination rate profiles is provided

Modelado, simulación y diseño de diodos láser de alto brillo

Esta tesis recoge el trabajo realizado sobre modelado, simulación y diseño de diodos láser en forma de embudo (tapered). Estos dispositivos presentan un brillo y una calidad de haz superiores a otros láseres de semiconductor de potencia, pero su funcionamiento complejo hace conveniente la utilización de herramientas de simulación en el proceso de optimización. Se ha profundizado en la comprensión del funcionamiento global de estos dispositivos, así como en los mecanismos que deterioran y limitan su rendimiento. Se ha desarrollado un simulador tridimensional para diodos láser en forma de embudo operando en régimen continuo. El trabajo de modelado se ha centrado en la implementación bi- y tri-dimensional de los modelos eléctricos y térmicos, como extensión de modelos unidimensionales previamente existentes, y en la optimización de su acoplo con un modelo óptico desarrollado externamente. Las ecuaciones de Poisson y continuidad para electrones/huecos se resuelven autoconsistentemente con acopla-miento a un modelo bidimensional de propagación del haz. Se ha desarrollado un método original de calibración de los parámetros del modelo, que ha demostrado la validez del modelo a través de su buena concordancia con resultados experimentales en distintos diseños y materiales. Han sido identificados los dos principales mecanismos responsables del deterioro de la calidad del haz: filtrado espacial insuficiente en la sección recta y autoenfoque del haz debido a la lente inducida por los portadores. Se exponen diversas alternativas para con-trarrestar estos efectos, incidiendo en el papel de elementos clave como los deflectores de haz y la reflectividad de los espejos. Igualmente, se estudian estrategias de optimiza-ción en función de varios parámetros de diseño, proponiéndose unos criterios generales que ayuden a mejorar sus prestaciones

Simulation and geometrical design of multi-section tapered semiconductor optical amplifiers at 1.57 µm

Fully integrated semiconductor master-oscillator power-amplifiers (MOPA) with a tapered power amplifier are attractive sources for applications requiring high brightness. The geometrical design of the tapered amplifier is crucial to achieve the required power and beam quality. In this work we investigate by numerical simulation the role of the geometrical design in the beam quality and in the maximum achievable power. The simulations were performed with a Quasi-3D model which solves the complete steady-state semiconductor and thermal equations combined with a beam propagation method. The results indicate that large devices with wide taper angles produce higher power with better beam quality than smaller area designs, but at expenses of a higher injection current and lower conversion efficiency

Analysis of the performance of tapered semiconductor optical amplifiers: role of the taper angle

The role of the taper angle in the performance of tapered semiconductor optical amplifiers emitting at 1.57 um is analyzed by means of simulations with a self-consistent steady state electro-optical and thermal simulator. The results indicate that the self-focusing caused by carrier lensing is delayed to higher output powers for devices with taper angle slightly higher than the free diffraction angle and therefore a higher power with beam quality is attainable with these devices at the expenses of a lower efficienc