Measurements of the nonlinear refractive index in scattering media using the Scattered Light Imaging Method - SLIM

Abstract

The Scattered Light Imaging Method (SLIM) was applied to measure the nonlinear refractive index of scattering media. The measurements are based on the analysis of the side-view images of the laser beam propagating inside highly scattering liquid suspensions. Proof-of-principle experiments were performed with colloids containing silica nanoparticles that behave as light scatterers. The technique allows measurements with lasers operating with arbitrary repetition rate as well as in the single-shot regime. The new method shows advantages and complementarity with respect to the Z-scan technique which is not appropriate to characterize scattering media.

High-order optical nonlinearities in plasmonic nanocomposites—a review

“…The beam propagation along the sample was recorded by two CCD cameras placed on the laser beam axis and in the direction perpendicular to the beam axis. For the analysis of the images collected in the transverse direction the scattered light imaging method (SLIM) [172,173] was used. Figure 11(b) displays the behavior of the output beam radius as a function of the incident intensity, after the beam passed through a 2 mm long cell (∼8 Rayleigh lengths), containing the quintic-septimal medium.…”

Intensity correlation scan (IC-scan) technique to characterize the optical nonlinearities of scattering media

“…Among them, the wellestablished Z-scan technique suffers with the distortion of the transmitted intensity beam pro le and wavefront induced in the scattering media, which causes the intensity transmitted by the small aperture (closed aperture (CA) Z-scan) to show large uctuations at each step during sample translation. Experiences in highly scattering media, such as colloids containing SiO 2 nanoparticles (NPs) suspended in acetone, show that the uctuations in the CA Z-scan curve can be larger than the peak-valley transmittance variations, making its characterization unfeasible [34]. Similar experiments show a low signal-to-noise ratio in the CA Z-scan curves when vitreous humor [37], ammonium dihydrogen phosphate crystals [38], and liquid crystals [39,40] were studied.…”

“…Similar experiments show a low signal-to-noise ratio in the CA Z-scan curves when vitreous humor [37], ammonium dihydrogen phosphate crystals [38], and liquid crystals [39,40] were studied. To overcome this limitation in scattering media, some adaptations to existing (or new) techniques have been developed [33][34][35]. In the spatial domain, the scattered light imaging method (SLIM) was proposed to collect light scattered by the turbid medium, in the direction perpendicular to propagation, to image the evolution of the laser beam diameter along propagation [34].…”

“…Here, the NL refractive index is determined by analyzing the divergence angle variations induced by the self-focusing (or self-defocusing) effect, even in a single shot con guration. Thus, unlike NL transmission techniques that suffer with light scattering, SLIM can only be used when scattering is relevant and the samples are thick enough to analyze light propagation within scattering media [34]. In addition to measuring the NL refractive index, SLIM was also recently applied to discriminate the NL extinction due to NL absorption and NL scattering contributions in turbid media [41].…”

Third-order optical measurements of porphyrin compounds using Dark-field and D4σ-Z scan imaging techniques

“…Because of the large discrepancy found in the literature related to third-order optical nonlinear (NL) coefficients an unbiased comparison of different materials sometimes is very difficult. Hence, development of new NL techniques is still relevant and subject to active research [1,2,3] to find simple and sensitive ways to measure the optically induced NL refraction (NLR) despite of the presence of relatively high NL absorption (NLA). Therefore, the newly introduced imaging techniques: DFZ-scan [4] and D4σ-Zscan [5,6] are applied here to demonstrate their ability to measure the thirdorder NL refractive index, n 2 , in presence of large NLA coefficient, β, as it is often the case with organic materials.…”