Low Power and Compact Silicon Thermo-Optic Switch Based on Suspended Phase Arm Without Support Beams

Abstract

A low power and compact thermo-optic switch based on $1\times 1$ Mach-Zehnder interferometer structure is demonstrated with the thermal isolation structure fabricated with a new backside etching process. The adjacent SiO2 and underlying silicon around phase arm are removed to suppress the thermal diffusion. Benefiting from the backside anisotropic etching process and front protecting photoresist used in underlying silicon removal, there are no support SiO2 beams in air trenches avoiding about 10% of extra thermal diffusion. At 1550 nm for TE mode, a low switching power (P $_{\pi } $ ) 0.48 mW is obtained with $450~\mu \text{m}$ thermo-optic interaction length ( $\text{L}_{\mathrm {TO}}$ ) representing a $\text{P}_{\pi }\cdot \text {L} _{\mathrm {TO}}$ product of only $0.22~\text {mW} \cdot \text {mm}$ , indicating a high thermal efficiency with a compact footprint. The 10% - 90% response time of the switch is $530~\mu \text{s}$ , including a rise time of 150 $\mu \text{s}$ , and a fall time of $380~\mu \text{s}$ . Compared with the switch without isolation structure, the switching power of the proposed switch is reduced more than 17 times, needing only 5.6% of the original value.