source: © 2017 Optical Society of America
The addition of optoacoustic sensing to optical microscopy may supplement fluorescence contrast with label-free measurements of optical absorption, enhancing biological observation. However, the physical dimensions of many optoacoustic systems have restricted the implementation of hybrid optical and optoacoustic (O2A) microscopy to imaging thin samples in transmission mode or to ex-vivo investigations. Here we describe a miniaturized optoacoustic sensor, based on a ?-phase-shifted fiber Bragg grating embedded in an acoustic cavity, which is virtually invisible to the optical path and can be seamlessly integrated into any conventional optical microscope. The new sensor enables, for the first time to our knowledge, entirely optical O2A intravital microscopy in epi-illumination mode, demonstrated by label-free optoacoustic and second-harmonic generation images of a mouse abdomen and ear. Our technique greatly simplifies the integration of acoustic detection in standard microscopes and could therefore make optoacoustic microscopy more accessible to the biomedical community. [Read More…]
Fig. 5. Schematic depiction of the O2A microscopy setup: A standard inverted microscope with laser sources for optoacoustic and non-linear optical imaging is combined with galvanometric mirrors for fast laser raster scanning. The sensor is mounted on the microscope objective, with a tunable CW laser coupled to the embedded ?-FBG. The inset shows the 3D printed platform supporting an anesthetized mouse and mounted on a ??? positioning stage. DM, dichroic mirror; BP, bandpass filter; PH, pinhole; ND, neutral density filter; BS, beam splitter; PMT, photomultiplier tube; OA, optoacoustic; DAQ, data acquisition card.