Simulation and fabrication of amorphous silicon rib-type arrayed waveguide grating

Abstract

Amorphous silicon SOI-AWG device with 59% extra high refractive index difference (Δ) and the transmission spectrum of AWG's device indicated the insertion loss, crosstalk and side-lobe were lower than -3.5 dB, -25 dB and -45 dB, respectively, by 3D beam propagation method were investigated in this study. The smallest chip size of the whole device is smaller than 4.5 cm x 1.2 cm, and the highest coupling loss of the rib waveguide for single mode fiber was about -1.68 dB. Based on the simulation results, the device will be really fabricated by thin-film deposition, photolithography and dry-etching processes. Optical measurements of amorphous silicon films indicated, the more refractive index of a-Si films indicated possessing less point defects, dangling bonds, voids, and more hydrogen content and silicon nano-crystallized structures. Meanwhile, the more point defects, dangling bonds, silicon nano-crystallized structures, and less voids and hydrogen content result in larger extinction coefficient. Therefore, we adopted the suitable deposition rate and refractive index at 1550nm wavelength were 0.6 nm/s and 3.5012, respectively, to perform real AWG fabrication. From atomic force microscopy (AFM) analysis revealed the increased argon/silane flow rate and RF power wattage, and decreased operating vacuum would increase surface roughness. High-resolution transmission electron microscopy (HRTEM) analysis indicated amorphous silicon films mainly had amorphous structure with few silicon nano-crystallized structures, point defects and voids might affect the value of the refractive index and reliability. The structures of the a-Si films all indicated amorphous structure by x-ray diffraction (XRD) analysis.