Intensity dependent self-action of a continuous wave (CW) or pulsed optical beam can lead to spatial or spectral effects upon propagation through a nonlinear medium, which can be described as an intensity dependence of the refractive index, known as self-phase modulation (SPM). In this work, we revisit the nonlinear optical propagation of a CW and a CW mode-locked (CW-ML) high repetition rate [ ∼ megahertz (MHz)] laser propagating through pure ethanol in regions of very low optical absorption (800 nm) or very high absorption (1480 nm, 1560 nm). Spatial and spectral SPM and Z -scan experiments were performed to clarify the origin of the third-order nonlinear optical response in the different optical excitation regimes. From spatial SPM and Z -scan at either CW or CW-ML MHz regime, a thermal nonlinear response was determined to be the origin of the nonlinearity at 800 nm or 1480 nm, 1560 nm region, with the nonlinear refractive index response of the order of 10 − 4 − 10 − 9 c m 2 / W . From the spectral SPM, the non-thermal origin of the nonlinearity, arising from electronic or nuclear processes in the ethanol, was determined, and values of the order of 10 − 13 − 10 − 16 c m 2 / W were obtained, depending upon the spectral region. The results were supported by theoretical calculations using the nonlinear Schrödinger equation for the spectral behavior or Fresnel–Kirchhoff integral for the spatial results and clarify some of the misinterpreted results reported in the literature, besides complementing other nonlinear refraction data available at different wavelengths from 355 nm to 1560 nm.

We report experimental studies of spatial self-phase modulation (SSPM) in liquid suspensions of semiconducting MoS 2 , MoSe 2 , MoTe 2 , WS 2 , semimetallic ZrTe 2 , WTe 2 , and metallic NbS 2 , NbSe 2 using linearly and circularly polarized light with CW or CWmode-locked (ML) excitation lasers. For the semiconducting suspension of nanoflakes, excitation above and below the bandgap was performed. The results show that the intensity-dependent changes in the refractive index responsible for SSPM and associated ring formation are explained as arising from thermal origin. Measured values of the effective thermal nonlinear coefficient, n 2,th , range from ∼4.3 × 10 −7 to ∼4.2 × 10 −5 cm 2 /W, depending on the absorption strength of the suspension, and are independent of the optical excitation regime (polarization and laser mode of operation). The use of circularly polarized light to obtain the same results as seen with linearly polarized light is fundamental to complement the results, demonstrating that at the spectro-temporal regimes studied, thermal nonlinearity explains well the ring formation, in addition to providing the original SSPM results for NbS 2 , ZrTe 2 , and WTe 2 .

Phosphotellurite based glasses and glass-ceramics have interesting features such as low characteristic temperatures, high glass forming ability, promising optical properties and a broad transparency window from UV to NIR.

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We correct the unit of pulse duration in Table 1 [J. Opt. Soc. Am. B 38, 1104 (2021)JOBPDE0740-322410.1364/JOSAB.418635]. The correct unit is femtosecond (fs).