Unidirectional ultraviolet lasing in a GaN ring cavity with slit

Abstract A ring cavity can ensure the overlap between the gain and resonance regions. It prevents unnecessary energy loss and makes it highly attractive for achieving high-performance on-chip integrated lasers. In this paper, we designed and fabricated floated GaN microring cavity with a slit for directional ultraviolet lasing. The fabricated sample’s uniqueness is presented in numerical simulation and then studied with optical measurement. Our research reveals that a small compressive stress exists in the samples due to the AIN buffer layer, and suspending the sample will release the existing compressive stress within the cavity and Si substrate. The stress release can influence the photoluminescence (PL) properties with position relevance. Cavity with a slit structure has a notable impact on the emission direction. For a cavity with an outer diameter of 35.6 μm, an inner diameter of 18.4 μm, and a slit width of 3.5 μm, ultraviolet lasing emission at a wavelength of 367.7 nm with a Q-factor up to 966.5 is observed at locations away from the slit. However, a slight decrease in lasing performance occurs when closer to the slit, as evidenced by observations at 368.3 nm, where the nearby Q-factor is lower, at 822.1. Furthermore, we have facilitated directional emission in the cavity with slit. This asymmetry introduced into the light emission process holds great potential for developing multifunctional coherent light sources in optoelectronic integration.