Low-Threshold InP Nanowire Hetero-Photonic Crystal Surface-Emitting Lasers

Nanowire photonic crystal surface-emitting lasers (PCSELs) hold considerable promise as on-chip coherent light sources for photonic integrated circuits. However, they face stringent demands regarding laser performance and compactness of the active region. To address these challenges, we designed and evaluated the lasing characteristics of InP nanowire hetero-PCSELs. These PCSELs feature a tightly compact, hexagonally shaped inner lasing region with side lengths ranging from 1.5 to 15 μm, surrounded by a larger, off-resonant outer photonic crystal designed to lower the lasing threshold. Inner PCSELs with an area smaller than the focus of the pump light but with side length exceeding 3 μm showed markedly reduced threshold power and threshold gain compared to large area PCSELs. The threshold reductions are attributed to back reflection enhancement at the heterolattice interface as the laser energy lies in the forbidden photonic gap of the outer photonic crystal array. This study paves the path toward ultracompact, low-threshold electrically pumped nanowire PCSELs for integration into photonic circuits.