High-optical-intensity 2D AlGaAs laser arrays

Abstract

ABSTRACT High power diode laser arrays have been demonstrated using relatively simple manufactured water-cooled packages. The layerstructure ofthe graded-index separate confinement heterostructure (GRIN-SCH) using AlGaAs material systems were employedfor the 0.8 .tm-emission. The laserbars havebroad-area stripes(70 jim)with apitch ofl5O jim and acavity length of500 jim.A maximum power of4O W per 1-cm-laser-barwas obtained for the layer structure with 10-nm-thick quantum well. We stack15 laser bar modules (laser block) and fabricated two-dimensional laserarrays with 45 laser bars, consisting of3 laser blocks.The total output power is about 680 W, which corresponds to an intensity ofabout 110 W/cm2. The reliability data of 200-W laser blocks are shown to be about 5000 hours extrapolated by 2000 hours' data.Keywords: A1GaAs, high power, CW, water-cooled heatsink, 2-D laser arrays, laser block 1. INTRODUCTION High power laser diodes arrays are increasingly used forpumping solid state media. For industrial applications, the laser arraysare too expensive. Two main costs ofthe laser arrays are semiconductor laser bars and the packaging.One ofthe most typical solid state media is Nd:YAG crystal, which canbe optically pumped with 807-nm light. Semiconductorlasers which can lase at 807 nm have been developed using active layers with (Al)GaAs, In(Al)GaAs, InGaAsP and so on'.Although an aluminum-free active layerexhibits very good reliability2, in general, it would be difficultto grow active layers witha lasing wavelength within 807 3 nm because ofusing two kinds ofV materials (As and P). Therefore, we treatAlGaAs activelayers forthe low cost material. In this paper, we investigate the effecton laser baroutput characteristics ofchanging the quantumwell thickness.The other main reason forthe high costs is that ofthe packaging one with water coolers. Many cooling systems for laser arrayshave been developed, which include coolers using impingement3, silicon microchannels4, and copper microchannels5. Thethermal resistance ofimpingement coolers is relatively high and the cost ofmicrochannel structures is also high. Therefore, toachieve low thermal resistance and low cost at the same time, we developed a new thin cooler consisting of3 copper sheets,