Regrowth-free blue GaN-based photonic crystal surface-emitting lasers with triangular air holes

We report the successful realization of a room-temperature blue GaN photonic crystal surface-emitting laser (PCSEL) diode fabricated using a regrowth-free approach. By employing a square lattice photonic crystal structure with modified triangular air holes, we achieve robust two-dimensional single-mode lasing. The device operates with a threshold current density of 5.2 kA/cm2 and emits a Gaussian-shaped beam with exceptionally low beam divergence, measured at 1.15 mrad (0.066°). Furthermore, the symmetry-breaking nature of the triangular air holes enforces a stable linear polarization perpendicular to the long edge of the triangle. This work demonstrates that high-beam-quality blue PCSELs can be achieved using non-regrowth fabrication processes with simple hole geometry, paving the way for high-performance blue laser sources.