Influence of Band-Edge Frequency Non-Uniformity in Ultra-Large-Area Photonic-Crystal Surface-Emitting Lasers

Photonic-crystal surface-emitting lasers (PCSELs), which are based on a two-dimensional (2D) optical resonance at a band edge of a photonic band structure, feature ultra-large-area single-mode lasing oscillation with scalable output power. In this paper, we theoretically investigate the influence of the band-edge frequency non-uniformity in ultra-large-area PCSELs, which can be caused by carrier-induced or temperature-induced refractive-index change during operation. First, we perform a perturbation analysis to derive an analytical condition to maintain single-mode lasing in the presence of the band-edge frequency non-uniformity, and reveal that it is important to increase not only the threshold gain difference but also the frequency difference between the fundamental mode and higher-order modes. Next, we perform numerical simulations on lasing characteristics of 3-mm-diameter PCSELs with non-uniform band-edge frequency distributions, and investigate the robust design against gradually changed frequency distributions or random frequency fluctuations.