Broadband photodetectors are of major significance in spectroscopy, imaging, and communication. Here, we demonstrate a waveguide integrated 1L-MoS2 photodetector for SWIR operating at zero bias with no dark current and having a responsivity up to ~100V/W. Our results pave the way for developing broadband MoS2 photodetectors from visible to IR.
KEYWORDS: Optoacoustics, Acoustics, In vivo imaging, Microrings, Silicon photonics, Point spread functions, Detection theory, Design and modelling, Vascular imaging, Ultrasonography
We demonstrate an ultra-wideband silicon-photonics acoustic detector (SPADE) with high sensitivity and signal fidelity, enabling highly detailed vascular imaging with resolutions comparable to optoacoustic microscopy. Our design is based on a planarized micro-ring resonator coated with an elastomer cladding in which the sensing is performed. The design of the guided optical mode and the use of planarization lead to high signal fidelity and a tomographic point-spread function that is in excellent agreement with the theoretical prediction. The new SPADE platform is demonstrated in vivo for imaging the vasculature of a mouse ear in high definition.
SignificanceOptical-resolution optoacoustic microscopy (OR-OAM) enables label-free imaging of the microvasculature by using optical pulse excitation and acoustic detection, commonly performed by a focused optical beam and an ultrasound transducer. One of the main challenges of OR-OAM is the need to combine the excitation and detection in a coaxial configuration, often leading to a bulky setup that requires physically scanning the ultrasound transducer to achieve a large field of view.AimThe aim of this work is to develop an OR-OAM configuration that does not require physically scanning the ultrasound transducer or the acoustic beam path.ApproachOur OR-OAM system is based on a non-coaxial configuration in which the detection is performed by a silicon-photonics acoustic detector (SPADE) with a semi-isotropic sensitivity. The system is demonstrated in both epi- and trans-illumination configurations, where in both configurations SPADE remains stationary during the imaging procedure and only the optical excitation beam is scanned.ResultsThe system is showcased for imaging resolution targets and for the in vivo visualization of the microvasculature in a mouse ear. Optoacoustic imaging with focal spots down to 1.3 μm, lateral resolution of 4 μm, and a field of view higher than 4 mm in both lateral dimensions were demonstrated.ConclusionsWe showcase a new OR-OAM design, compatible with epi-illumination configuration. This setup enables relatively large fields of view without scanning the acoustic detector or acoustic beam path. Furthermore, it offers the potential for high-speed imaging within compact, miniature probe and could potentially facilitate the clinical translation of OR-OAM technology.
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