GaN Ultraviolet Laser based on Bound States in the Continuum (BIC)

摘要

Optical bound states in the continuum (BICs), realizing substantial suppressionof out-of-plane radiative losses, have been utilized to realize strong lightconfinement and optical modes with high quality-factor (Q). Lasing actionswith narrow linewidths based on optical BIC modes have been demonstratedin the near-infrared and the visible ranges, but BIC-based lasers in the ultraviolet(UV) region have not been reported. As light sources possessing wavelengthsat the UV scale are essential in various fields, the strategy to designcompact UV lasers based on high-Q modes and directional emissions is highlydesirable. Here, the first BIC-based laser in the UV region is demonstrated bydesigning a 1D periodic resist structure on top of a GaN film. Using the symmetric-protected BIC mode, the fabricated laser is having a directional singlemodelasing emission with a small full-width at half-maximum of 0.10 nm andbeam divergence of 1.5°. The lasing action is observed with a periodic structurearea corresponding to a structure side length as small as 8 μm. Moreover,the wavelength control of the UV lasing is achieved by varying the period andtemperature. This work provides strategies to design UV lasers having a smallfootprint together with narrow-linewidth and out-of-plane emissions.