As a new type of semiconductor laser, photonic crystal surface-emitting lasers (PCSELs) feature large-area single-mode surface emission with high power and high beam quality. The unique features of single-mode lasing over a large area active region are implemented by the in-plane optical feedback from two-dimensional (2D) photonic crystal cavities. In larger PCSEL cavities, the lasing gain threshold becomes similar for the fundamental and high-order modes, which degrades single-mode operation. Here, we investigate the impact of carrier injection on PCSEL modes by controlling the injection area and the gain mode interaction. Optical and electrical simulations are carried out to calculate the gain mode overlapping factor for different p electrode designs. We fabricated 250 × 250 µm2 photonic crystal cavities with different p electrode sizes for injection area control. The PCSEL device characterization results show that devices with an electrode size to cavity side length ratio of 0.6 have the maximum slope efficiency and a lower lasing threshold with a single lobe beam profile. Such selective carrier injection can also provide gain-guided resonance in the PCSEL cavities and enhance optical gain in the fundamental mode while suppressing gain in the high-order modes.
