Optimization of InGaAsP/GaAs laser diode processing for high-power operation

InGaAsP/GaAs aluminum-free laser diodes are currently attracting attention as an emerging competitor for widely used AlGaAs-based lasers emitting at 0.87-0.75 μm, especially for Nd-YAG laser pumping (λ=0.808 μm). These lasers have already demonstrated such advantages as narrow transverse far-field pattern, absence of uncoated mirror facet oxidation under high-power operation, low series resistance and processing ease and offer a strong promise of longer lifetime. In a recent paper the authors have studied the cavity length dependence of operational characteristics of InGaAsP/GaAs 0.8 μm SCH laser diodes and argued that long-cavity lasers may be advantageous for high-power operation because they are less subjected to the effects of excess carrier leakage from the active region to the waveguide and cladding layers. Low series resistance and thermal resistance of long-cavity laser diodes and bars suggest an additional incentive for their use for high-power CW application. The authors are reporting series resistance as low as 0.03 Ω and record-low thermal resistance of 1 C/W obtained for 0.8 μm InGaAsP/GaAs laser diodes with cavity length above 2 mm. Active region overheating was determined comparing CW light-current characteristic with those measured under pulse operation at different temperatures and it was shown not to exceed 10°C at the CW driving current of 6 A