Experimental verification of backscattering CARS spectroscopy on opaque media

Abstract

The applicability of a recently suggested coherent anti-Stokes Raman spectroscopic (CARS) reflection technique to investigatiom of strongly absorbing materials was tested. The underlying principle is that the CARS signal generated in the surface layers of the sample is detected as a beam which is backscattered from the surface of an opaque medium rather than in transmission. A special experimental arrangement was used which allowed CARS spectra to be obtained with reasonable signal strength. As an example, experimental results for a TS6 (hexa-t,4diynylene di-p-toluenesu1phonate)polydiacetylene single crystal are presented. Spectra obtained at different angles of incidence are discussed.

Epi-detected hybrid coherent Raman micro-spectroscopy

“…We do not observe this effect, so we confirm again that the epi-detected signal is real. Similar temporal behaviors of CARS/CSRS in These experimental results confirm that the hybrid CARS micro-spectroscopy can be used in epi-detection configuration and potentially applied to opaque media [26,27].…”

Interface-Specific χ(4) Coherent Raman Spectroscopy in the Frequency Domain

“…From a theoretical study, we can consider that the interface has only a few molecular diameter thickness. In contrast, the χ (3) spectroscopy, i.e., CARS in the reflection configuration, , is supposed to probe the “interfacial” region of wavelength-order thickness. Therefore, the region probed by the χ (3) spectroscopy should be essentially regarded as bulk.…”

Novel interface‐selective even‐order nonlinear spectroscopy

“…Therefore, if the vibrational reswww.lpr-journal.org onance is achieved with only visible or NIR light, the above-mentioned problems are solved. Based on this idea, we recently developed the two types of the interfaceselective χ (4) Raman spectroscopy in the frequency domain [25,27], i.e., CARS-type homodyne-detection χ (4) Raman and inverse-Raman-type heterodyne-detection χ (4) Raman, in which the vibrational resonance is realized by the Raman process (CARS: coherent anti-Stokes Raman scattering [53][54][55][56][57][58][59]). Because χ (4) Raman does not employ IR but uses only visible or NIR light, it can be applied to interfaces buried in thick IR absorbers if they are transparent for visible or NIR light.…”