Analysis of Pulses Bandwidth and Spectral Resolution in Femtosecond Stimulated Raman Scattering Microscopy

Luigi Sirleto,Rajeev Ranjan,Maria Antonietta Ferrara

doi:10.3390/app11093903

Luigi Sirleto, Rajeev Ranjan + Show 1 more

Open Access

https://doi.org/10.3390/app11093903

Copy DOI

Abstract

In the last decade, stimulated Raman scattering (SRS) imaging has been demonstrated to be a powerful method for label-free, non-invasive mapping of individual species distributions in a multicomponent system. This is due to the chemical selectivity of SRS techniques and the linear dependence of SRS signals on the individual species concentrations. However, even if significant efforts have been made to improve spectroscopic coherent Raman imaging technology, what is the best way to resolve overlapped Raman bands in biological samples is still an open question. In this framework, spectral resolution, i.e., the ability to distinguish closely lying resonances, is the crucial point. Therefore, in this paper, the interplay among pump and Stokes bandwidths, the degree of chirp-matching and the spectral resolution of femtosecond stimulated Raman scattering microscopy are experimentally investigated and the separation of protein and lipid bands in the C-H region, which are of great interest in biochemical studies, is, in principle, demonstrated.

Highlights

Over the past ten years, stimulated Raman scattering (SRS) microscopy has been investigated in nanophotonics [1,2,3,4] as well as in biophotonics as an analytical, label-free, noninvasive technique with unique cellular and tissue imaging capabilities [5,6,7,8]
From Equations (2) and (3), we found that τ·τ0 ≈ 4 ln 2|group delay dispersion (GDD)| ≈ 2 ln 2/|β|; this product is considered a direct measure of the chirp parameter β for τ τ0 [19]
In order to carry out cross-correlation between Ti:Sa and OPO, both sources are focused inside the TPA detector, by inserting an optical delay line (Newport MOD MILS200CC) between the Ti:Sa and the microscope, we introduce an optical delay in the Ti:Sa beam; at each step of the delay line, the signal is acquired

Summary

Introduction

Over the past ten years, stimulated Raman scattering (SRS) microscopy has been investigated in nanophotonics [1,2,3,4] as well as in biophotonics as an analytical, label-free, noninvasive technique with unique cellular and tissue imaging capabilities [5,6,7,8]. Information obtained by autocorrelation measurements allows us to monitor the pulse duration and chirp of the laser beam, which are very important parameters to optimize the non-linear interaction in microscopy.

Results

Conclusion