Over 20 W DBR tapered semiconductor laser with passive current control

Power scaling in tapered semiconductor lasers requires a sufficiently long effective amplification length and a sufficiently large gain area. High injection currents, however, intensify thermal accumulation and lateral-mode competition within the device. A p-side-down bonding configuration shortens the heat-dissipation path, but in a common-electrode design, the larger injection area and lower equivalent resistance of the power amplifier (PA) section reduce the current supplied to the master oscillator (MO) section, making stable seed generation difficult. We therefore establish a three-dimensional current-injection model and propose a passive current-control method based on the ratio of n-side bonding-wire counts. Simulations show that the bonding-wire configuration affects the fraction of current supplied to the MO section. Experimental comparisons of 16/50, 16/30, and 16/10 configurations on the same device further show that reducing the number of PA bonding wires redistributes more current toward the MO, while excessively reducing the PA wire count increases the device resistance and current nonuniformity. Based on this trade-off, a 16/30 configuration is adopted for a p-side-down, common-electrode distributed Bragg reflector (DBR) tapered semiconductor laser emitting at 967 nm, with a 2 mm MO section and a 5 mm PA section. Under continuous-wave operation at a heat-sink temperature of 25 °C, the device delivers a maximum output power of 26 W and a peak wall-plug efficiency of 52.2%. At 30 A, it produces 22.9 W with M² (1/e²) = 1.01 and 13.8 W in the central lobe. These results show that adjusting the n-side bonding-wire ratio can regulate the MO/PA current-partition ratio while retaining the thermal advantage of p-side-down bonding and increasing the output power.