Miniaturized ultrasound detector arrays in silicon photonics using pulse transmission amplitude monitoring

Abstract

Silicon photonics holds promise for a new generation of ultrasound-detection technology, based on optical resonators, with unparalleled miniaturization levels, sensitivities, and bandwidths, creating new possibilities for minimally invasive medical devices. While existing fabrication technologies are capable of producing dense resonator arrays whose resonance frequency is pressure sensitive, simultaneously monitoring the ultrasound-induced frequency modulation of numerous resonators has remained a challenge. Conventional techniques, which are based on tuning a continuous wave laser to the resonator wavelength, are not scalable due to the wavelength disparity between the resonators, requiring a separate laser for each resonator. In this work, we show that the Q-factor and transmission peak of silicon-based resonators can also be pressure sensitive, exploit this phenomenon to develop a readout scheme based on monitoring the amplitude, rather than frequency, at the output of the resonators using a single-pulse source, and demonstrate its compatibility with optoacoustic tomography.

Silicon photonic acoustic detector (SPADE) using a silicon nitride microring resonator

“…9 shows the obtained results, along with the results previously measured in Ref. [24] using a silicon SPADE with a Q-factor of 2.2 × 10 4 . The results show the responsivities of ∼ 0.9 pm/kPa and ∼ 0.2 pm/kPa, for the MRR-SPADE and the silicon SPADE, respectively.…”

“…Second, the resonance wavelength of each sensing element could be individually tuned via controlled UV exposure, thus enabling a single source to interrogate a series of microrings in parallel [36] . Third, pulse interferometry (PI) [24] , [37] , [38] could facilitate parallel interrogation for an arbitrary distribution of resonance wavelengths, albeit with some sensitivity loss due to power splitting between resonators. However, the sensitivity may be regained if PI is used in a burst mode, where higher peak powers are used for the interrogation source without increasing the average power [39] .…”

Parallel interrogation of the chalcogenide-based micro-ring sensor array for photoacoustic tomography

“…For example, it was shown in Ref. 48 that using pulse transmission amplitude monitoring for parallel readout of arrays could cause orders of magnitude loss in sensitivity compared to the single-element approach. In PAT, the imaging resolution is determined by the detecting bandwidth of the micro-ring sensor.…”