title: A transparent broadband ultrasonic detector based on an optical micro-ring resonator for photoacoustic microscopy.
abstract: Photoacoustic microscopy (PAM) does not rely on contrast agent to image the optical absorption contrast in biological tissue. It is uniquely suited for measuring several tissue physiological parameters, such as hemoglobin oxygen saturation, that would otherwise remain challenging. Researchers are designing new clinical diagnostic tools and multimodal microscopic systems around PAM to fully unleash its potential. However, the sizeable and opaque piezoelectric ultrasonic detectors commonly used in PAM impose a serious constraint. Our solution is a coverslip-style optically transparent ultrasound detector based on a polymeric optical micro-ring resonator (MRR) with a total thickness of 250 μm. It enables highly-sensitive ultrasound detection over a wide receiving angle with a bandwidth of 140 MHz, which corresponds to a photoacoustic saturation limit of 287 cm(-1), at an estimated noise-equivalent pressure (NEP) of 6.8 Pa. We also established a theoretical framework for designing and optimizing the MRR for PAM.
authors.affiliation: 1] Department of Biomedical Engineering, Northwestern University, Evanston IL 60208 [2].
authors.forename: Hao
authors.initials: H
authors.lastname: Li
authors.affiliation: 1] Department of Biomedical Engineering, Northwestern University, Evanston IL 60208 [2] Department of Mechanical Engineering, Northwestern University, Evanston IL 60208 [3].
authors.forename: Biqin
authors.initials: B
authors.lastname: Dong
authors.affiliation: Department of Mechanical Engineering, Northwestern University, Evanston IL 60208.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: 1] Department of Biomedical Engineering, Northwestern University, Evanston IL 60208 [2] Department of Ophthalmology, Northwestern University, Chicago IL 60611.
authors.forename: Hao F
authors.initials: HF
authors.lastname: Zhang
authors.affiliation: Department of Mechanical Engineering, Northwestern University, Evanston IL 60208.
authors.forename: Cheng
authors.initials: C
authors.lastname: Sun
mesh_terms: D008853:Microscopy / Q000379:methods*; D061088:Photoacoustic Techniques; D014465:Ultrasonics