Monolithic two‐dimensional surface‐emitting diode laser arrays mounted in the junction‐down configuration

We report on the first achievement of large area (0.5 cm2) monolithic two‐dimensional surface‐emitting arrays mounted in the junction‐down configuration. Device fabrication involves dry etching of 45°, and vertical micromirrors with ±2° tolerances and <0.2 μm RMS smoothness, integration of 100‐μm‐thick current‐spreading electrodes for minimizing ohmic loss, large area packaging, and mounting to heat exchangers for long pulse and minimum chirp operation. Uniform lasing is achieved from 0.2×0.5 cm2 and 0.5×1 cm2 active area junction‐down monolithic arrays (120 and 600 emitters, respectively) using 100 μs long pulses at a 1% duty cycle. Differential quantum efficiencies of ≥ (R18)40% and 7% are achieved for rows of 12 emitters, and for 0.2×0.5 cm2 active area arrays, respectively. The decrease in efficiency with increased area is found to be due to current leakage, which in turn limits the 2‐D array emitted optical‐power density to 150 W/cm2. Wavelength chirp in these devices is measured to be <4 nm at twice...