# Phase modulated pulse interferometry for simultaneous multi-channel ultrasound detection

## TL;DR

This paper introduces a phase modulation pulse interferometry method enabling simultaneous ultrasound detection with multiple high Q-factor optical resonators without requiring overlapping spectra, simplifying multi-channel optical ultrasound sensing.

## Contribution

The paper presents a novel phase modulation pulse interferometry technique for parallel interrogation of non-overlapping high Q-factor resonators in optical ultrasound detection.

## Key findings

- Successful demonstration of four-channel ultrasound detection
- Single photodetector per ultrasound detector suffices
- Method overcomes spectral overlap limitations

## Abstract

In optical detection of ultrasound, resonators with high Q-factors are often used to maximize sensitivity. However, in order to perform parallel interrogation, conventional interferometric techniques require an overlap between the resonator spectra, which is difficult to achieve with high Q-factor resonators. In this paper, a new method is developed for parallel interrogation of optical resonators with non-overlapping spectra. The method is based on a phase modulation scheme for pulse interferometry (PM-PI) and requires only a single photodetector and sampling channel per ultrasound detector. Using PM-PI, parallel ultrasound detection is demonstrated with four high Q-factor resonators.

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Source: https://tomesphere.com/paper/1901.05163