Simultaneous Multi-Channel Ultrasound Detection via Optical Resonators

Yoav Hazan, Amir Rosenthal

Research output: Contribution to conferencePaperpeer-review


In optical detection of ultrasound, high Q-factors resonators are often used to maximize sensitivity.
However, parallel interrogation by conventional interferometric techniques require an overlap between
the resonator spectra, which is difficult to achieve with high Q-factor resonators. In this work, a new
method is developed for parallel interrogation of optical resonators with non-overlapping spectra. The
method, based on a phase modulation scheme for pulse interferometry (PM-PI), requires only a single
photodetector and sampling channel per ultrasound detector - making this method scalable.
The general scheme of PM-PI composes of a wideband pulse laser connected to an unbalanced MachZehnder interferometer (MZI) with a phase modulator on one of its arms. The phase is switched between
two values with a difference of π/2. The outputs of the MZI are connected to numerous optical resonators.
The output of each resonator is switched between two interferometric states, which together enable us
to monitor wavelength shifts of its resonance. PM-PI was tested with 4 channels sampled simultaneously,
measuring peak-to-peak resonance shift of 1 GHZ, i.e. twice larger than the resonance width. Such a large
shift cannot be properly measured using conventional CW laser interrogation.
In conclusion, we developed a novel scheme for parallel interrogation of resonator-based interferometric
detectors of ultrasound. Our scheme is based on a variation of pulse interferometry, in which the pulses are
phase modulated at the input of the resonators. The modulation enables the coding in time of two interference
states, which facilitates digital demodulation of the desired signals from simple power measurements. PMPI overcomes a major limitation of interferometric detectors of ultrasound - the inability to simultaneously
interrogate several resonators with non-overlapping spectra. Ultrasound detector arrays based on PM-PI
may be used to significantly improve the performance of hybrid imaging systems for which no compatible
ultrasound detector array technology exist.
Original languageAmerican English
StatePublished - 2019
EventOASIS 7th Conference and Exhibition on Electro-Opics - Tel-Aviv, Israel
Duration: 1 Apr 20192 Apr 2019
Conference number: 7th


ConferenceOASIS 7th Conference and Exhibition on Electro-Opics
Abbreviated titleOASIS
Internet address


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