Cathodoluminescence Study of V-defects in AlGaAs-based High-power Laser Bars
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0994-F07-03
Cathodoluminescence Study of V-defects in AlGaAs-based High-power Laser Bars Matthieu Pommies1, Manuel Avella1, Alonso Martin1, Juan Jimenez1, Myriam Oudart2, and Julien Nagle3 1 Fisica de la Materia Condensada, Universidad de Valladolid, ETSII, Paseo del Cauce s/n, Valladolid, 47011, Spain 2 Alcatel Thales, 3-5 lab, RD 128, Palaiseau, 91767, France 3 Thales Research and Technology, RD 128, Palaiseau, 91767, France ABSTRACT High-power semiconductor lasers are required to be more and more powerful, efficient and reliable for applications such as solid-state lasers pumping, materials processing, and thermal printing among others. The understanding of the degradation mechanisms is essential to improve the high power laser reliability. The highest power emission is achieved with multi-emitter laser cm-bars, which present problems related to packaging induced stress. A very harmful defect in this type of devices is the so-called V defect. We present herein a study of these defects using cathodoluminescence imaging, the role of packaging is discussed. INTRODUCTION High power laser diodes are being used in different applications, e.g., solid state laser pumping, materials processing, optical communications, printing machines, among other (1, 2). The high emission power required for those applications is achieved with multimode broad emitter laser arrays supplying continuous wave optical output powers up to a few hundred Watts (2). The crucial issue for high power laser diodes is reliability. To understand the degradation of these devices is a major concern for the development of the next generation of high power laser diodes. One of the key issues concerns the heat removal during laser operation. The high power of these devices induces a significant heating of the active parts of the device, especially at the mirror facet, where the energy losses are responsible for the catastrophic optical damage (COD) (3,4). A harmful degradation mode of the laser bars is related to the formation of V-defects, which are not observed in narrow emitters lasers, but are exclusive of broad emitters (2,5). The origin of these defects is a matter of controversy; it has been related to the packaging induced stresses (5,6). Effective heat sinks are necessary to remove the heat generated during laser operation, but the soldering of the laser bars to the heat sink introduces packaging stresses, which are more pronounced in the central part of the bar being almost relaxed towards the bar ends (6). The stresses are due to the dissimilar materials that compose the laser structure; on the other hand, the thermal expansions of these disimilar materials produces thermo-mechanical stresses during laser operation (2,7). We present herein a cathodoluminescence (CL) study of V defects in aged AlGaAs/GaAs 808 nm cm bar lasers, the main characteristics of these defects are described and the possible origins are discussed. EXPERIMENTAL Graded Index-Separate Confinement Heterostructure AlGaAs/GaAs-based lasers emitting at 808 nm consisting of 25 br
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