Design of Low-Loss High-Contrast Grating Reflector for 850 nm Vertical Cavity Surface Emitting Laser

We designed a high-contrast grating (HCG) reflector with low absorption loss for an 850 nm vertical cavity surface emitting laser (VCSEL). The HCG reflector composed of Si and ZnS as high refractive index materials is analyzed by simulation. The results show that HCG using Si as the grating material can provide a broad reflection bandwidth. However, due to the absorption loss of Si, the peak reflectivity remains relatively low. In contrast, ZnS exhibits significantly lower absorption loss at the 850 nm, enabling the design of an HCG that meets the requirements of 850 nm VCSEL. An HCG reflector with ZnS/SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> in transverse electric (TE) polarization mode is designed. The reflectivity of the designed HCG is greater than 99% in the wavelength range of 805-920 nm, the peak reflectance at 850nm is 99.95%. The structural parameters of the HCG reflector demonstrate a large tolerance range, maintaining high reflectance even at grating tilt angles from 0° to 12.6°, thereby reducing the fabrication complexity of HCG reflector. The ZnS/SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> HCG reflector have significant advantages in improving VCSEL integration, reducing light loss and manufacturing process difficulty.