Laser-induced breakdown mediated interaction between stimulated Raman scattering and four-wave mixing for broadband coherent radiation

Abstract

Broadband coherent radiation is of great importance for spectroscopy, precision metrology, and nonlinear optics. In this work, precise control of laser-induced breakdown (LIB) in binary liquids is achieved through the synergistic tuning of the benzene (C6H6)–carbon tetrachloride (CCl4) volume ratio and the laser focusing conditions, leading to a significant enhancement of high-order stimulated Raman scattering (SRS). The addition of C6H6 reduces the ionization threshold of mixtures and modifies the characteristics of the LIB process. The plasma generated subsequently promotes the occurrence of four-wave mixing (FWM) and influences the interaction process between SRS and FWM. At the volume ratio of 19:1 (CCl4 to C6H6), the 8th-order Stokes SRS is achieved. The aperture-limited spectra reveal a correlation between higher-order SRS features and FWM. The pump-energy-dependent behaviors of the SRS and transmitted energies provide further evidence that the introduction of C6H6 facilitates the FWM process and reduces the breakdown threshold. By employing the self-resonant stimulated Raman approach, 6th-order coherent anti-Stokes Raman scattering (CARS) and 11th-order Stokes SRS are achieved, producing broadband coherent radiation spanning from −2749 to 5068 cm−1. This work offers a new route for broadband coherent radiation and Raman comb generation in binary liquid systems.