Multidirectionally distributed feedback photonic crystal lasers

TLDR

The study examines the lasing mode of a two‑dimensional photonic crystal laser employing in‑plane multidirectional distributed feedback, combining theory and experiment. The authors identify a Γ point where lasing arises from coupling of six equivalent Γ–X lightwaves and normal diffraction, calculate distinct field patterns at each band edge, and experimentally measure lasing characteristics and polarization to confirm the correspondence between wavelengths and band‑edge fields. Experiments show single‑mode, broad‑area lasing at room temperature, with measured wavelengths matching calculated band‑edge fields, confirming that multidirectional coupling drives coherent 2D lasing and that polarization can be tuned via lattice defects.

Abstract

The lasing mode of a two-dimensional (2D) photonic crystal laser with in-plane multidirectionally distributed feedback effect is analyzed theoretically and experimentally. From an investigation of the Bragg diffraction conditions at several points in the photonic band diagram where lasing is expected, we identify a particular \ensuremath{\Gamma} point at which lasing occurs due to the coupling of lightwaves propagating in six equivalent \ensuremath{\Gamma}-X directions and diffraction normal to the substrate surface. In order to investigate the lasing mode in detail, the distribution of the electromagnetic field at the band edges at the \ensuremath{\Gamma} point is calculated, and each band edge is found to have a different field pattern. The lasing characteristics of the 2D photonic crystal laser at the lasing wavelength corresponding to the \ensuremath{\Gamma} point are measured. Single-mode lasing over a broad circular area is observed by microelectroluminescence measurements under pulsed conditions at room temperature. We also demonstrate the correspondence between the measured lasing wavelengths and calculated band edges by comparing the polarization characteristics with the calculated distribution of the electromagnetic field. The results indicate that 2D coherent lasing oscillation does, in fact, occur due to the multidirectional coupling effect in the 2D photonic crystal. From the theoretical calculation, we show that the polarization patterns of the lasers can be controlled by introducing artificial lattice defects.