Created by sebastien.popoff on 04/07/2020
Endoscopy combining photoacoustic and fluorescence imaging with a small footprint
Achieving optical-resolution photoacoustic imaging can currently only be obtained using endoscopy. It usually implies a quite bulky endoscope and/or a low signal-to-noise detection. In this paper, the authors present a technique that combines wavefront shaping through a multimode fiber, to scan the focus spot, with a single-mode fiber-based ultrasound sensor to achieve a high signal-to-noise with a small footprint (250 by 125 microns).
Created by sebastien.popoff on 14/06/2013
A noninvasive measure of the transmission matrix in scattering media using the photo-acoustic effect
Optical wavefront shaping allows imaging or focusing of light in strongly scattering media at a depth where usual microscopy techniques fail. However, wavefront shaping techniques usually require captors (like a CCD array) or probes (like fluorescent entities) to guide the focusing of light or to characterize the system for imaging purposes. Recently, [X. Xu, H. Liu and L.V. Wang, Nat. Photon., 5, 154, (2011)] and [X. Xu, H. Liu and L.V. Wang, Nat. Photon., 7, 300, (2013)] (see Retrieving an optical scale resolution with light focusing guided by ultrasound) have shown how to use ultrasound to noninvasively guide light focusing in a scattering medium. This method uses an iterative optimization scheme for focusing on each target. This limits the applications for imaging due to the time requirements. In this paper, the authors use the photo-acoustic effect to measure the transmission matrix that links the optical field on the surface of a spatial light modulator (SLM) modulating the input light to the optical field on different points inside a scattering medium. This knowledge of this matrix allows selective focusing on multiple points and detection of targets buried in the medium.