Miniature probe for all‐optical double gradient‐index lenses photoacoustic microscopy

Abstract

A novel all-optical double gradient-index (GRIN) lens optical-resolution photoacoustic microscopy (OR-PAM), termed as DGL-PAM, is demonstrated. The miniature probe consists of a single-mode fiber and double GRIN lenses for optical focusing and a miniature fiber Fabry-Perot sensor for ultrasound detection. The new design is simple and realizes high resolution with long working distance (WD) by virtue of the double GRIN lenses. The overall size of the probe is 2.7 mm in diameter. High lateral resolution of 3.7 μm (at 532 nm laser wavelength) and long WD of 5.5 mm are achieved. In vivo OR-PAM of mouse ear demonstrates the imaging ability of DGL-PAM. Since precise alignment of optical and acoustic foci is not needed, the proposed DGL-PAM is relatively easy to implement. It has potential to be developed as a low-cost, disposable OR-PAM probe and for endoscopic applications. The proposed double GRIN lenses for making miniature endoscopic probes can also be applied to other modalities, such as optical coherence tomography and confocal fluorescence microscopy, to enable high resolution and long WD.

Photoacoustic Imaging of Lithium Metal Batteries

“…Figure 2(c) shows the lateral profile of photoacoustic signals with scanning step size of 0.5 µm. The profile was fitted by an edge spread function (ESF) [25]. Then, we took the first derivative of the ESF to obtain a linear spread function and extracted its full width at half maximum (FWHM) as lateral resolution, which was 3.3 µm.…”

“…Photoacoustic imaging is based on the photoacoustic effect that light absorbed by a material can be converted into heat and the subsequent thermoelastic expansion to generate an acoustic wave. In the past 20 years, this has been extensively explored in the biomedical imaging field to reveal a wide variety of endogenous or exogenous absorbers. − Since light is highly absorbed by most metals, we anticipate that Li metal can be visualized and quantified by photoacoustic imaging. In this paper, for the first time, we demonstrate that photoacoustic imaging can be exploited to map Li protrusions in Li metal batteries in 3D.…”

Advances in Endoscopic Photoacoustic Imaging

“…Due to the introduction of a US transducer, US imaging can be incorporated seamlessly. Alternatively, an all optical US sensor, such as a Fabry-Pérot interferometer and microresonator, can be also applied to detect a generated PA signal [13][14][15][16][17][18][19][20]. The intensity of the generated PA signal is proportional to the local absorption coefficient of the tissue, the light intensity, and the Grüneisen parameter, which represents thermoacoustic conversion efficiency.…”

PMN-PT/Epoxy 1-3 composite based ultrasonic transducer for dual-modality photoacoustic and ultrasound endoscopy

“…A piezoelectric transducer or all-optical ultrasound (US) sensor can be used to detect these generated ultrasonic waves, or the PA signals. An all-optical US sensor, such as a Fabry-Pérot interferometer or microresonator, is able to provide wide detection bandwidth, resonance-free acoustic detection spectrum, and high resolution [[4], [5], [6], [7], [8], [9], [10], [11]]. However, it still presents challenges for US detection.…”