# Coherent Vibrational Anti-Stokes Raman Spectroscopy Assisted by Pulse Shaping

## TL;DR

This paper reviews how pulse shaping improves coherent anti-Stokes Raman spectroscopy for better imaging and analysis in biophotonics.

## Contribution

The paper provides a comprehensive review of passive and active pulse shaping strategies in CARS spectroscopy.

## Key findings

- Passive pulse shaping techniques like hybrid CARS and spectral focusing CARS are effective for spectral resolution.
- Active pulse shaping using SLMs enhances CARS by enabling precise control of laser pulses.
- Combining active and passive shaping with AOPDFs improves CARS performance experimentally demonstrated in the study.

## Abstract

Coherent anti-Stokes Raman scattering (CARS) is a powerful nonlinear spectroscopic technique widely used in biological imaging, chemical analysis, and combustion and flame diagnostics. The adoption of pulse shapers in CARS has emerged as a useful approach, offering precise control of optical waveforms. By tailoring the phase, amplitude, and polarization of laser pulses, the pulse shaping approach enables selective excitation, spectral resolution improvement, and non-resonant background suppression in CARS. This paper presents a comprehensive review of applying pulse shaping techniques in CARS spectroscopy for biophotonics. There are two different pulse shaping strategies: passive pulse shaping and active pulse shaping. Two passive pulse shaping techniques, hybrid CARS and spectral focusing CARS, are reviewed. Active pulse shaping using a programmable pulse shaper such as spatial light modulator (SLM) is discussed for CARS spectroscopy. Combining active pulse shaping and passive shaping, optimizing CARS with acousto-optic programmable dispersive filters (AOPDFs) is discussed and illustrated with experimental examples conducted in the authors’ laboratory. These results underscore pulse shapers in advancing CARS technology, enabling improved sensitivity, specificity, and broader applications across diverse scientific fields.