Magic silicon dioxide for widely tunable integrated photonics

TL;DR

This paper introduces a novel silicon dioxide material with tunable thermo-optic properties, enabling bidirectional wavelength tuning and low thermal crosstalk in integrated photonic devices, advancing optical computing and sensing technologies.

Contribution

The authors demonstrate a method to deterministically tune silicon dioxide's thermo-optic properties, achieving bidirectional wavelength shifts and significantly reducing thermal crosstalk in integrated photonics.

Findings

Up to 10-fold improvement in thermo-optic tunability.

Demonstration of athermal ring resonators with minimal shifts.

Implementation of a single-heater tunable coupled ring optical waveguide.

Abstract

Integrated photonic circuits have transformed data communication, biosensing, and light detection and ranging, and hold wide-ranging potential for optical computing, optical imaging and signal processing. These applications often require tunable and reconfigurable photonic components, most commonly accomplished through the thermo-optic effect. However, the resulting tuning window is limited for standard optical materials such as silicon dioxide and silicon nitride. Most importantly, bidirectional thermal tuning on a single platform has not been realized. For the first time, we show that by tuning and optimizing the deposition conditions in inductively-coupled plasma chemical vapor deposition (ICPCVD) of silicon dioxide, this material can be used to deterministically tune the thermo-optic properties of optical devices without introducing significant losses. We demonstrate that we can deterministically integrate positive and negative wavelength shifts on a single chip, validated on amorphous silicon carbide (a-SiC), silicon nitride (SiN) and silicon-on-insulator (SOI) platforms. We observe up to a 10-fold improvement of the thermo-optic tunability and, in addition, demonstrate athermal ring resonators with shifts as low as 1.5 pm/{\deg}C. This enables the fabrication of a novel tunable coupled ring optical waveguide (CROW) requiring only a single heater. In addition, the low-temperature deposition of our silicon dioxide cladding can be combined with lift-off to isolate the optical devices resulting in a decrease in thermal crosstalk by at least two orders of magnitude. Our method paves the way for novel photonic architectures incorporating bidirectional thermo-optic tunability.