Compared with conventional histology, Stimulated Raman scattering (SRS) microscopy provides high specificity, fast speed and label-free histopathological analysis of the lesions by mapping their chemical compositions. However, benchtop SRS microscopy is limited to its bulky size to access the tissues of interest in-vivo inside the human body. To enable SRS in-vivo label-free histology, here, we develop an implantable fiber-scanning SRS endoscope. The endoscope is capable of providing hyperspectral Raman images at C-H and C-D regions. We use a double-clad single-mode fiber to deliver the pump and Stokes femtosecond pulses through the core and collect back-scattering signals through the outer cladding. To remove the nonlinear background induced by the pulse interactions in the fiber, we temporally separate the two pulses by tuning a delay line. We custom-design a micro-objective made of high-dispersive ZnSe glass which enables a simultaneously focusing and recombining the two pulses at spatial and time domains on the sample for excitation. A piezo actuator is designed to resonantly scan the fiber cantilever with spiral patterns. By establishing this technology, we expect the SRS endoscope to have great potential in medical applications such as label-free image-based diagnosis and surgical guidance.
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