Invited Article: CARS molecular fingerprinting using sub-100-ps microchip laser source with fiber amplifier

Hiroaki Yoneyama,Kazuhiro Sudo,Philippe Leproux,Akihito Inoko,Hideaki Kano,Vincent Couderc

doi:10.1063/1.5027006

Abstract

We have developed an ultrabroadband multiplex coherent anti-Stokes Raman scattering (CARS) microspectroscopic system using a supercontinuum (SC) seeded by sub-100-ps (85 ps) laser pulses with a sub-MHz (0.82 MHz) repetition rate. Because of the high peak power and ultrabroadband spectral profile of the SC, we can efficiently generate multiplex CARS signals in the spectral range of 600–3600 cm−1, which covers the entire molecular fingerprint region, as well as the C—H and O—H stretching regions. Due to the high peak power of the new laser source, the exposure time (pixel dwell time) for CARS imaging of polymer beads was reduced to less than 1 ms (0.8 ms), which was limited by the readout time of a CCD camera. Owing to the improvement in CARS spectral quality, clear molecular fingerprinting was achieved for living HeLa cells at different phases in the cell cycle.

Highlights

Nonlinear Raman spectroscopic imaging is a powerful method of performing label-free microscopic molecular imaging.[1,2,3,4,5,6] Coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) are two of the major techniques of nonlinear Raman spectroscopic imaging
The laser pulses are divided into two with one part being used as the pump radiation (ω1) for the CARS process and the other being seeded into a photonic crystal fiber (PCF) to generate a SC, which is used as the Stokes radiation (ω2) for the CARS process
The Im[ χ(3)] spectrum at each spatial position was calculated from the raw CARS spectra using the maximum entropy method (MEM).[23,30]

Summary

Introduction

Nonlinear Raman spectroscopic imaging is a powerful method of performing label-free microscopic molecular imaging.[1,2,3,4,5,6] Coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) are two of the major techniques of nonlinear Raman spectroscopic imaging. A sub-nanosecond laser source has been used as the master laser source

Methods

Results

Conclusion