Multimodal label-free optical microscopy for in vivo and in situ imaging of human tissue represents a challenge especially when nonlinear optical techniques are used. One possible solution to address this challenge is the use of specific hand-held and endomicroscopy probes, based on optical fibers, capable to image at the same time the chemical composition and the morphological structure of the tissues. Nonlinear optical imaging techniques, including TPEF, SHG, spectral focusing CARS, combined with spectral domain OCT are capable to give functional, molecular and morphological information. Since nonlinear optical microscopy and SD-OCT require ultrashort pulses to efficiently image the targeted sample, the development of such probes requires specific attention to high peak power and ultrashort pulse delivery at the focal plane. Different optical fiber technologies for femtosecond pulse delivery are experimentally investigated in order to suggest an optical fiber that fulfill at the same time the requirements for above mentioned imaging modalities. We investigated three different approaches that are normally considered for ultrashort pulse delivery: large-mode area (LMA) fiber, hollow-core photonic bandgap fiber and kagome hollow-core fiber from GLOphotonics. We tested this three fibers on our label-free multimodal imaging platform which is capable to simultaneously acquire TPEF, SHG, spectral focusing CARS and SD-OCT. From our investigation, we identify the fiber which better satisfy the requirements of all the above mentioned imaging modalities in terms of dispersion profile and transmission of high energy pulses. Imaging capabilities are shown on a biological tissue of interest.
|