Effects of Lattice Types on GaN-Based Photonic Crystal Surface-Emitting Lasers

GaN-based photonic crystal (PC) surface emitting lasers with different lattice types including hexagonal, square, and honeycomb lattice were fabricated and characterized. Laser characteristics including threshold conditions, lasing spectra, polarization, and divergence angle of devices with different lattice have been studied and discussed. The threshold energy density of the device with honeycomb, hexagonal, and square lattice was measured to be approximately 1.6, 2.3, and 3.8 mJ/cm² at room temperature, showing superior characteristics of applying honeycomb as PC lattice patterns. Moreover, the experimental results were matched well to the theoretical prediction using the multiple scattering method. Finally, the laser characteristics of devices with three lattice types such as divergence angle and degree of polarization (DOP) were analyzed and discussed. The device with honeycomb lattice shows low threshold, high DOP of 86%, and low divergence angle of 1.3° among three lattice types, demonstrating its potential in the future surface emitting laser sources.