Observation of spatial self-phase modulation induced via two competing mechanisms

Nonlinear Optical Properties of the Topological Material Bi2Se3 Family for the Application of an Ultrafast Pulse Laser Based on the Occupied and Unoccupied Band Structures

The Bi2Se3 family can exhibit many intriguing topological insulator properties, including a narrow bandgap and strong surface states, which show excellent nonlinear optical properties. Thinning bulk Bi2Se3 family materials to create a low-cost photoelectric modulation device and explaining the mechanisms of nonlinear optical differences in different types of materials remain challenges. Based on liquid-phase exfoliation technology and tapered fiber, this work prepared optoelectronic modulation devices for various samples within the Bi2Se3 family, quantitatively compared their nonlinear optical properties, and analyzed the sources of differentiation using the occupied and unoccupied multiband structure theory. The results correspond well to the phenomena observed in the ultrafast laser, which will provide strong support for the design of higher performance photoelectric devices based on topological insulators.

Visible optical nonlinearity of vanadium dioxide dispersions

Vanadium dioxide (VO2), a correlated oxide compound, is one of the functional materials extensively studied in solid state physics due to its attractive physical properties. However, the nonlinear optical response of VO2 and related all-optical applications have been paid less attention. Here, the nonlinear refractive index (n 2) and third-order nonlinear susceptibility (χ (3)) of VO2 dispersions have been acquired to be 3.06 × 10-6 cm2 W-1 and 1.68 × 10-4 esu at a wavelength of 671 nm, and 5.17 × 10-6 cm2 W-1 and 2.83 × 10-4 esu at a wavelength of 532 nm via the spatial self-phase modulation (SSPM) and spatial cross-phase modulation (SXPM) effects in the visible regime, respectively. Based on the excellent nonlinear optical properties of VO2 dispersions, the proof-of-principle functions such as optical logic or-gates, all-optical switches, and inter-channel information transfer are implemented in the visible wavelength. The experimental results on the response time of VO2 to light indicate that the formation of diffraction rings is mainly an electronically coherent third-order nonlinear optical process. The experimental results show that the VO2 dispersions exhibit an excellent nonlinear optical response and may lay the foundation for the application of VO2-based all-optical devices.

Identification of aggregated 2D cobalt tellurides using a spatial self-phase modulation technique

We report a previously unreported application of the spatial self-phase modulation (SSPM) technique for recognizing solute-solvent interaction in a suspension of 2D material. Broadband optical absorption of the 2D Co₂Te₃ leads to a nonlinear optical (NLO) susceptibility for the monolayer, i.e., χ M o n o(3) of 1.5 ×10^-9 (3.3 ×10^-9) esu at 532 (632) nm, which is 1-2 orders higher than for the 2D CoTe and CoTe₂. The fine structure of the SSPM patterns is analyzed to explore the foundations of the observed NLO effects. With increasing polarity of the liquid media, a change of 2D Co₂Te₃ from homophonous dispersion to aggregation occurs, as confirmed from in situ optical microscopy and UV-vis absorption spectroscopy. As a result, type-I (thickest outer ring) SSPM ring patterns are converted to type-II (thinnest outer ring) SSPM ring patterns. Therefore, using SSPM with a CW laser as an optical tool to identify solvent-polarity-induced aggregation in 2D materials is possible.