Aiming at the epitaxial structure of the high-power 885nm laser diodes, the factors limiting the further increase of the output power and the power conversion efficiency were investigated. According to the analysis, the epitaxial structure of the laser diodes was optimized, and the influence of the waveguide layer thickness on the carrier absorption loss and the series resistance was theoretically simulated. The results showed that the asymmetric waveguide structure with the thickness ratio of the N-side and the P-side of 6:4 can reduce the carrier absorption loss to the greatest extent. Based on the simulation results, the 885nm laser bars with the optimized epitaxial structure were fabricated and tested under the ambient temperature of 25℃ in a quasi-continuous wave mode of 250μs and 200Hz. The slope efficiency reaches 1.26W/A, while the series resistance is only 1.2mΩ. The power of 277.6W is achieved at 250A injection current and the maximum power conversion efficiency exceeds 64%.
KEYWORDS: Semiconductor lasers, Resistance, High power lasers, Laser systems engineering, Structural design, Diode pumped solid state lasers, Solid state lasers, Laser welding, Lithium, Cladding
High-power GaAs-based semiconductor lasers are the most efficient source of energy for converting electrical into optical power. 940nm diode lasers are used directly or as pump sources for Yb:YAG solid-state lasers, and are widely used in laser cladding and other fields. Improving electro-optic conversion efficiency and reliable output power are urgent requirements for current research hotspots and industrial laser systems. In this paper, we use an asymmetric epitaxial structure of InGaAs/AlGaAs, which reduces the optical loss and resistance, and adopt better cavity surface technology to present 940nm 1-cm quasi-continuous micro-channel cooling (MCC) laser bars. The lasers are tested under a high duty cycle of 9.6% (600us,160Hz) at 25°C with output power of 660.05W, electro-optic conversion efficiency of 64.71% at 600A and slope efficiency of 1.16 W/A. The peak efficiency reaches 72.4%. The increased efficiency results from a lower threshold current and a lower series resistance. Furthermore, the output power of 1025W (1000A) has been confirmed at a duty cycle of 4% (400us,100Hz).
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