Low-Loss Silicon Waveguides and Grating Couplers Fabricated Using Anisotropic Wet Etching Technique

Abstract

We report low-loss silicon waveguides and efficient grating coupler to couple light into them. By using anisotropic wet etching technique, we reduced the side wall roughness down to 1.2 nm. The waveguides were patterned along the

Low-Loss Slot Waveguides with Silicon (111) Surfaces Realized Using Anisotropic Wet Etching

“…Since this is a completely chemical process and strongly depends on the crystallographic orientation of the etched surface, ideally we should expect an ultra-smooth surface with atomic level irregularity. Previously sub-dB propagation loss in silicon strip waveguides has been demonstrated using TMAH-based wet etching process (Lee et al, 2001;Debnath et al, 2016). In this work, by combining dry and wet etching processes, we managed to reduce the propagation loss of a slot waveguide with 200-nm slot width from 10.5 to 3.7 dB/ cm and for a strip waveguide from 2.7 to 1 dB/cm.…”

Fabrication of Arbitrarily Narrow Vertical Dielectric Slots in Silicon Waveguides

“…In order to smoothen the trench side wall roughness, we used Tetramethylammonium hydroxide (TMAH) based wet etching process. Using this process we have previously demonstrated low-loss silicon strip and slot waveguides [10,11]. Details of such smoothening process can be found in [11].…”

Fabrication of silicon slot waveguides with 10nm wide oxide slot

“…Then trenches of different widths and lengths were etched through the thin SiO2 and top silicon layers. The side-walls of the trenches were smoothened by Tetramethylammonium hydroxide (TMAH) based wet etching process [7,8]. After the trenches were created, another thermal oxidation step was performed.…”