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arXiv · 2105.07846

Real-time ultrasound sensing with a mode-optimized photonic crystal slab

Eric Y. Zhu·Maria Charles-Herrera·Cory Rewcastle·Raanan Gad·Li Qian·Ofer Levi
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Abstract

Integrated photonic sensors can provide large scale, flexible detection schemes. Photonic crystal slabs (PCS) offer a miniaturized platform for wideband, sensitive ultrasound detection by exploiting the photoelastic effect in water. However, poor modal overlap with the sensing medium and non-negligible absorption loss of the aqueous medium have previously limited PCS sensor performance. In this study, we detail the development and optimization of a PCS-based acoustic sensor, by adding to it a low-loss high-index polymer cladding layer. Exploiting a mode-optimized TM-like optical resonance present in a PCS, with high bulk index sensitivity (>600 nm/RIU) and quality factor Q (>8000), we demonstrate real-time ultrasound-sensing at a noise equivalent pressure (NEP) of 170 Pa (1.9 Pa/rt Hz). The PCS sensor is backside-coupled to optical fiber which, along with its intensity-based ultrasound-sensing architecture, will allow us to scale up easily to a 2D array. This work paves the way to a sensitive compact ultrasound detector for photoacoustic-based diagnostics and monitoring of tissue.

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Eric Y. Zhu, Maria Charles-Herrera, Cory Rewcastle, Raanan Gad, Li Qian, Ofer Levi. 2021-08-14. Real-time ultrasound sensing with a mode-optimized photonic crystal slab. https://doi.org/10.1364/ol.430431

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