Miniaturized CARS endomicroscopic probe with a large field of view using a MEMS mirror scanner – concept and design considerations

We present here the concept of a MEMS-mirror based nonlinear endomicroscopic probe for coherent anti-Stokes Raman scattering (CARS), two-photon excitation fluorescence (TPEF), and second harmonic generation (SHG). The rigid probe head is 5 mm in diameter and 4 cm in length, offering a large field of view (FOV) with a high numerical aperture (NA). It incorporates a double-core fiber delivering two excitation wavelengths of CARS in isolated cores, with a large cladding area to increase the collection efficiency of the nonlinear signal from the tissue. A diffractive grating element is included in the probe to compensate for the spatial offset of two emission cores.