Discrimination between two distinct nonlinear effects by polarization-resolved Z-scan measurements

Abstract

We investigated how the Z-scan technique can be explored to distinguish two types of nonlinear refractive effects by employing two distinct laser polarizations. It is possible that pure electronic, molecular orientation and thermal nonlinear effects may occur simultaneously during light-matter interaction. We found a way to discriminate and quantify two distinct nonlinear processes from Z-scan signals measured with linear and circular polarizations. This paper provides analytical equations for nonlinear refractions and in order to test them, we carried out measurements in CS2 and in a rhodamine-B solution, where electronic and orientational, and electronic and thermal nonlinearities mixing, respectively, are present.

Spatial Self-Phase Modulation of Optical Vortex Beams in Liquid Suspensions of Semiconducting, Semimetallic, and Metallic 2D Nanoflakes due to a Kerr-like Nonlinearity

“…In a study regarding CS 2 , Reichert et al discussed how the electronic nonlinear response has a strong polarization dependence, with a more pronounced effect for linearly polarized light. 25 This result is supported by Melhado et al, 26 which showed that electronic and orientational nonlinear effects are polarization-dependent, while thermal nonlinearities are not, an indication that the observed nonlinearities in our experiments are most likely of thermal origin. In a recent work, Bautista et al 20 discussed in detail the physical mechanisms responsible for SSPM of Gaussian beams interacting with liquid suspensions of 2D materials when CW or ML high repetition-rate lasers are employed.…”

“…In a study regarding CS 2 , Reichert et al discussed how the electronic nonlinear response has a strong polarization dependence, with a more pronounced effect for linearly polarized light . This result is supported by Melhado et al, which showed that electronic and orientational nonlinear effects are polarization-dependent, while thermal nonlinearities are not, an indication that the observed nonlinearities in our experiments are most likely of thermal origin.…”

Study of Impulsive Stimulated Raman Scattering Effects Using the Femtosecond Pump–Probe Z-Scan Technique

“…Actually, we verified that in our experimental setup, the excitation beam profile could not be described as a fundamental Gaussian beam; moreover, the thin sample approximation was not fully verified. Therefore, we used the known value of the CS2 sample nonlinear refractive index for hundred-femtosecond pulses, i.e., γref = 2 × 10 −6 cm 2 /GW [23,[25][26][27], as a reference value to calibrate our system and to obtain the Kerr nonlinearity of other samples, using the method described in [28], essentially exploiting the linear dependence of the Z-scan peak-valley amplitude ΔTpv on the nonlinear refractive index for small nonlinearities. Here, the peak-valley amplitude of the CS2 reference sample was ∆𝑇 = 13%, and thus, given the measured value ∆𝑇 of an unknown sample in the same excitation conditions, the associated refractive index is given by As evidenced by an attempt to fit the data with the commonly used simple theoretical model [20], assuming a TEM 00 Gaussian beam, thin sample and small nonlinearities, the experimental traces deviated substantially from the model.…”

Polarization Z-Scan Studies Revealing Plasmon Coupling Enhancement Due to Dimer Formation of Gold Nanoparticles in Nematic Liquid Crystals

“…Polarization z-scan allows for a comprehensive analysis of the material's anisotropic properties, revealing how nonlinear optical behavior changes with different polarizations [35][36][37][38][39][40][41]. In this report, we used the polarization z-scan technique to probe the interparticle plasmon coupling within AuNP dimers as well as establish their presence and structural characteristics.…”