Measurement of the surface-enhanced coherent anti-Stokes Raman scattering (SECARS) due to the 1574 cm(-1) surface-enhanced Raman scattering (SERS) mode of benzenethiol using low-power (<20 mW) CW diode lasers.

The surface-enhanced coherent anti-Stokes Raman scattering (SECARS) from a self-assembled monolayer (SAM) of benzenethiol on a silver-coated surface-enhanced Raman scattering (SERS) substrate has been measured for the 1574 cm(-1) SERS mode. A value of 9.6 ± 1.7×10(-14) W was determined for the resonant component of the SECARS signal using 17.8 mW of 784.9 nm pump laser power and 7.1 mW of 895.5 nm Stokes laser power; the pump and Stokes lasers were polarized parallel to each other but perpendicular to the grooves of the diffraction grating in the spectrometer. The measured value of resonant component of the SECARS signal is in agreement with the calculated value of 9.3×10(-14) W using the measured value of 8.7 ± 0.5 cm(-1) for the SERS linewidth Γ (full width at half-maximum) and the value of 5.7 ± 1.4×10(-7) for the product of the Raman cross section σSERS and the surface concentration Ns of the benzenethiol SAM. The xxxx component of the resonant part of the third-order nonlinear optical susceptibility |3 χxxxx((3)R)| for the 1574 cm(-1) SERS mode has been determined to be 4.3 ± 1.1×10(-5) cm·g(-1)·s(2). The SERS enhancement factor for the 1574 cm(-1) mode was determined to be 3.6 ± 0.9×10(7) using the value of 1.8×10(15) molecules/cm(2) for Ns.

Measurement of the Raman line widths of neat benzenethiol and a self-assembled monolayer (SAM) of benzenethiol on a silver-coated surface-enhanced Raman scattering (SERS) substrate.

Raman line widths of neat benzenethiol and a self-assembled monolayer (SAM) of benzenethiol on a surface-enhanced Raman scattering (SERS) substrate have been measured using a mini spectrometer with a resolution (full width at half-maximum) of 3.3 ± 0.2 cm(-1). Values of 7.3 ± 0.7, 4.6 ± 0.6, 2.4 ± 0.6, 3.2 ± 0.5, 8.8 ± 0.9, and 11.0 ± 1.1 cm(-1) have been determined for the Raman line widths of the 414, 700, 1001, 1026, 1093, and 1584 cm(-1) modes of neat benzenethiol. Values of 13.3 ± 0.7, 9.1 ± 0.7, 5.1 ± 0.6, 5.9 ± 0.6, 13.3 ± 0.5, and 8.7 ± 0.5 cm(-1) have been determined for the SERS line widths of a benzenethiol SAM on a silver-coated SERS substrate for the corresponding frequency-shifted modes at 420, 691, 1000, 1023, 1072, and 1574 cm(-1). The line widths for the SERS modes at 420, 691, 1000, 1023, and 1072 cm(-1) are about a factor of two larger than those of the corresponding Raman modes. However, the line width of the SERS mode at 1574 cm(-1) is slightly smaller than the corresponding Raman mode at 1584 cm(-1).