88×nm High-Efficiency Narrow Divergence Angle Laser Diodes With Coupled Waveguide Photonic Crystal

88x nm laser diodes with coupled waveguide photonic band crystal (CPBC) are designed and fabricated. By optimizing the optical confinement factor in the lightly doped coupled waveguide, the internal loss reduces to 0.52 cm
$^{-1}$
. The CPBC lasers achieve maximum power conversion efficiency of 65.57% under a continuous wave (CW) mode condition at room temperature, which is the highest reported value to our knowledge at 88x nm. The corresponding vertical divergence angel is 19.8°.