Measurement of third-order nonlinearities in selected solvents as a function of the pulse width

Abstract

We investigated the magnitude and origin of the nonlinear refraction in several solvents with the nonlinear ellipse rotation measurements as a function of the pulse duration in the range from 60fs to 2ps. Due to the presence of non-instantaneous nuclear contributions concurrently with the nearly instantaneous electronic nonlinearity, solvents present effective refractive nonlinearities that depend on the pulse duration. By proposing an empirical model where the nonlinearity grows exponentially with the pulse duration normalized to the response time, we could separate contributions from fast isotropic and slow nuclear reorientational nonlinearities. Z-scan measurements were also carried out to support our model.

Temporal and polarization dependence of the nonlinear optical response of solvents

“…The n 2,eff of the benzene derivatives at longer pulse widths (>10 ps) increases ∼8 × over the short pulse limit, primarily owing to their large n 2,l and n 2,r , while ∼4 × increase of n 2,eff is seen for chloroform for the same reasons. CCl 4 and alcohols with zero or negligible reorientational nonlinearities do not show a considerable increase of n 2,eff for longer pulse widths as expected from their response functions, e.g., n 2,eff of ethanol shows an increases of only ∼1.3 × for long pulse widths, which is consistent with the observation in [29]. Other NLO experiments such as Z-scan can be used to verify such predictions from BD measurements, as is shown for CS 2 [20,25].…”

“…The usefulness of the response function is that it can be used to predict and interpret the outcomes of other NLO experiments over a wide range of pulse widths. For example, for CS 2 , the response functions determined from our BD measurements in [20,25] have successfully predicted the pulse-width dependence of n 2,eff measured from Z-scan [20,29], as well as the results from other experiments, including degenerate four-wave mixing (DFWM) [20] and optical limiting [30]. In a recent study, our NLO response functions have also been used to interpret the results of mid-infrared supercontinuum generation from CS 2 -core optical fibers, which helps us understand new hybrid soliton dynamics as a result of the noninstantaneous NLR of CS 2 [31,32].…”

“…In a recent study, our NLO response functions have also been used to interpret the results of mid-infrared supercontinuum generation from CS 2 -core optical fibers, which helps us understand new hybrid soliton dynamics as a result of the noninstantaneous NLR of CS 2 [31,32]. Recently, seven solvents (also included in this work) were studied along with CS 2 using nonlinear ellipse rotation (NER) experiments [33,34] for a range of pulse widths, from which predictions of n 2,eff are given using an empirical model [29]. To open up more possibilities for other materials to be used in NLO applications, we follow the same BD methodology as [20,25] to perform extensive experimental characterizations on the third-order NLO response functions for 24 widely used organic solvents, as listed in Table 1.…”

Origin of the Kerr effect: investigation of solutions by polarization-dependent Z-scan

“…As the electronic contribution is instantaneous compared to the nuclear effects, by measuring the Kerr effect at different pulse widths, it is possible to separate these contributions. This has already been reported in the scientific literature by measuring the Kerr effect with pulse width from 100 fs to a few ps [19,20]. This allows for more in-depth studies of the NLO properties and for better understanding in which cases measured NLO properties resemble materials applicability in solid form as specific nuclear responses such as molecular reorientation will be much more limited.…”

“…Recently scientific groups have started to study the NLO properties of materials depending on incident laser beam polarization, by introducing λ/4 plate into the Z-scan setup [21]. Many works of polarization studies for inert gases [22], CS2 [23,24] and various solvents [19,23] have already been presented in the scientific literature, but similar in-depth studies of the NLO active organic dyes are insufficient, especially implementing the Z-scan method. Recently a paper was published regarding the separation of the thermal and the electronic contributions of Rhodamine B dissolved in methanol using polarization-resolved Z-scan measurements giving more insight for these effects in organic dyes [25].…”