# Amorphous silicon-carbide photonics for ultrasound imaging

## TL;DR

Amorphous silicon carbide is used to create compact, high-sensitivity sensors for ultrasound imaging, enabling detailed imaging with a miniaturized optical system.

## Contribution

The novel use of amorphous silicon carbide in microring sensors enables miniaturized, high-sensitivity optical ultrasound detection.

## Key findings

- a-SiC microring sensors achieved an optical finesse of 1320 and intrinsic sensitivity of 78 fm kPa−1.
- The system demonstrated a noise-equivalent pressure below 55 mPa/√Hz across 3.36 MHz to 30 MHz.
- High-resolution imaging of fine structures confirmed the practicality of the a-SiC-based system.

## Abstract

Photonic ultrasound sensors promise unparalleled spatial and temporal resolution in ultrasound imaging due to their size-independent noise figure, high sensitivity, and broad bandwidth. Optical materials can further improve performance and stability, but achieving small size, high sensitivity, and wide bandwidth remains challenging. This work introduces amorphous silicon carbide (a-SiC) for ultrasound sensing, offering strong optical confinement, low propagation loss, and high stability for miniaturized microring sensors. We demonstrate a compact detection system with a 20-transducers linear array coupled to a single bus waveguide. The sensors achieve an optical finesse of 1320 and intrinsic sensitivity of 78 fm kPa−1, leading to a noise-equivalent pressure below 55\documentclass[12pt]{minimal}
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\begin{document}$${{{\rm{mPa}}}}/\sqrt{{{{\rm{Hz}}}}}$$\end{document}mPa/Hz, calibrated from 3.36 MHz to 30 MHz. High-resolution imaging of fine structures validates real-world applicability. a-SiC is also easily integrated on most substrates due to its low deposition temperature. Our results position a-SiC as a promising solution for optical ultrasound sensing, combining miniaturization, low-loss, and high-sensitivity.

Amorphous silicon carbide microring sensors provide a compact platform for optical ultrasound detection. The authors demonstrate 20- element array coupled to single bus waveguide attains high finesse and sensitivity, enabling high-resolution imaging in a miniaturized, easily integrated system.