High-sensitivity frequency modulation CARS with a compact and fast tunable fiber-based light source

TL;DR

This paper introduces a compact, fast, and tunable fiber-based light source for frequency modulation CARS, enabling rapid wavelength switching and high sensitivity, suitable for medical and environmental applications.

Contribution

The development of a fiber-based light source that allows rapid wavelength tuning within 5 ms and enhances FM CARS sensitivity by 40 times.

Findings

40-fold sensitivity enhancement at 1 Hz LIA bandwidth

18-fold contrast improvement at 1 MHz LIA bandwidth

Wavelength tuning within 5 ms for rapid measurements

Abstract

Frequency modulation coherent anti-Stokes Raman scattering (FM CARS) is presented, using a compact as well as fast and widely tunable fiber-based light source. With this light source Raman resonances between 700 cm$^{-1}$ and 3200 cm$^{-1}$ can be addressed via wavelength tuning within only 5 ms, which allows for FM CARS measurements with frame-to-frame wavelength switching. Moreover, the functionality for high-sensitivity FM CARS measurements was integrated by means of fiber optics to keep a stable and reliable operation. The light source accomplished FM CARS measurements with a 40 times enhanced sensitivity at a lock-in amplifier (LIA) bandwidth of 1 Hz. For fast imaging with frame-to-frame wavelength switching at a LIA bandwidth of 1 MHz a 18-fold contrast enhancement could be verified, making this light source ideal for routine and out-of-lab FM CARS measurements for medical diagnostics or environmental sensing.