Measurement of the Third-Order Nonlinear Optical Susceptibility \(\chi^{(3)}\) for the \(1002-cm^{-1}\) Mode of Benzenethiol Using Coherent Anti-Stokes Raman Scattering with Continuous-Wave Diode Lasers

Abstract

The components of the third-order nonlinear optical susceptibility \(\chi^{(3)}\) for the \(1002-cm^{–1}\) mode of neat benzenethiol have been measured using coherent anti-Stokes Raman scattering with continuous-wave diode pump and Stokes lasers at 785.0 and 852.0 nm, respectively. Values of \(2.8 ± 0.3 × 10^{–12}\), \(2.0 ± 0.2 × 10^{–12}\), and \(0.8 ± 0.1 × 10^{–12} cm g^{–1} s^2\) were measured for the xxxx, xxyy, and xyyx components of \(|3\chi^{(3)}|\), respectively. We have calculated these quantities using a microscopic model, reproducing the same qualitative trend. The Raman cross-section \(\sigma_{RS}\) for the \(1002-cm^{–1}\) mode of neat benzenethiol has been determined to be \(3.1 ± 0.6 × 10^{–29} cm^2\) per molecule. The polarization of the anti-Stokes Raman scattering was found to be parallel to that of the pump laser, which implies negligible depolarization. The Raman linewidth (full-width at half-maximum) \(\Gamma\) was determined to be \(2.4 ± 0.3 cm^{–1}\) using normal Stokes Raman scattering. The measured values of \(\sigma_{RS}\) and \(\Gamma\) yield a value of \(2.1 ± 0.4 × 10^{–12} cm g^{–1} s^2\) for the resonant component of \(3χ^{(3)}\). A value of \(1.9 ± 0.9 × 10^{–12} cm g^{–1} s^2\) has been deduced for the nonresonant component of \(3\chi^{(3)}\).