Influence of Photonic Crystal Size and Lattice Constant on the Lasing Performance of UV-C PCSELs

Abstract Semiconductor lasers are compact, high-power coherent light sources across a broad wavelength range in the electromagnetic spectrum, including visible and infrared. Despite significant progress, they have yet to achieve the same performance for ultraviolet-C (UV-C) wavelengths (λ0 < 280 nm). Photonic crystal surface-emitting lasers (PCSELs) are a special type of semiconductor lasers and have shown high single-mode output powers and low-divergent beams for the infrared and visible spectral range. So far, UV-C PCSELs have only been demonstrated under optical pumping. Here, we investigate the influence of design parameters, such as the photonic crystal size and the lattice constant, on the lasing characteristics in optically pumped UV-C PCSELs through experiments and simulations. We show that the PCSELs are very sensitive to the lattice constant, where a range from 137 to 140 nm results in low-threshold devices. Also, the PCSEL size influences the threshold, which increases drastically for PCSELs < 70 μm. Finally, we explain the origin of high-angle lasing modes and how they can be suppressed by a small PCSEL size. For a device size around 70–90 μm in diameter, both a low-divergence far-field emission and a relatively low threshold can be achieved. Our findings provide a deeper understanding of UV-C PCSELs and pave the way for the development of future electrically driven high-power light sources.