Broadband antireflective coatings in the optical communication band deposited by ion-assisted reactive magnetron sputtering

Abstract

With the rapid development of silicon-based photonics, broadband anti-reflection coatings for the optical communication band are desired. Silica and silicon nitride with tunable refractive index were employed in anti-reflection coatings, which were deposited by ion-assisted reactive magnetron sputtering. The results showed that the average reflectance of 0.74% for single-layer coatings and below 0.12% after optimization for each sub-band. With the insertion layer, the anti-reflection band broadened and covered the optical communication band. Multi-layer coatings’ average reflectance was reduced to within 0.35%, with only 0.19% for four-layer coatings. Both single-layer and multi-layer coatings exhibited impressive deposition quality. For single-layer and multi-layer coatings, no obvious defects were found on the surface and cross-sectional morphology, and the roughness remained within 0.5 nm. In this work, anti-reflection coatings were deposited by ion-assisted reflective magnetron sputtering, featuring broadband low reflectance and high deposition quality, which is suitable for serving optical communication devices such as photodetectors and wide-tunable lasers.