Toward nonlinear endomicroscopy for exploration of the pulmonary airways: preliminary spectroscopic study of human lung tissue using a single-mode fibre

Abstract

We are developing a non-linear fibered endomicroscope for imaging the extracellular matrix collagen and elastin fibrillar networks during bronchoscopy. As a proof of concept, laser pulses at the output of a standard 2 meter long single-mode fibre have been obtained with pulse duration of about 50 fs and pulse energy up to 50 uJ, using a specially designed grism line for the dispersion compensation. With these pulses, we performed a spectroscopic characterization of the non-linear endogenous signal, consisting of two-photon fluorescence and second harmonic generation, and originated from human pulmonary tissue of various thickness, both in forward and backward geometry of signal collection, with excitation at 830 nm.