Nonlinear optical susceptibility of atomically thin WX₂ crystals

Authors

Mohammad Mokim, University of Rhode Island
Adam Card, University of Rhode Island
Feruz Ganikhanov, University of Rhode IslandFollow

Document Type

Article

Date of Original Version

2018

Abstract

We have studied tungsten diselenide (WSe₂) and tungsten disulfide (WS₂) monolayer materials in second harmonic generation spectroscopy and microscopy experiments. Ultra-broadband continuum pulses served as the fundamental beam while its second harmonic spectrum in the visible and ultraviolet (UV) range was detected and analyzed with a better than 0.3 nm spectral resolution (<2 >meV). We provide dispersion data and absolute values for χ⁽²⁾ for the materials within a photon energy range of 2.3–3.2 eV. Fine spectral features that were detected within the dispersion data for the optical nonlinearities indicate the impact of near bandgap exciton transitions. The fundamental bandgap of 2.35 eV and exciton binding energy of 0.38 eV were determined from the measurements for WS₂ monolayers while the corresponding values in WSe₂ monolayers were 2.22 eV and 0.71 eV. Ranges for the absolute values of the sheet nonlinearity for WS₂ and WSe₂ are shown to be 0.58–1.65 × 10⁻¹⁸ m²/V and 0.21–0.92 × 10⁻¹⁸ m²/V, correspondingly.

Citation/Publisher Attribution

Mokim, M., Card, A., & Ganikhanov, F. (2019). Nonlinear optical susceptibility of atomically thin WX₂ crystals. Optical Materials, 88, 30-38. doi: 10.1016/j.optmat.2018.11.003

Available at: http://dx.doi.org/10.1016/j.optmat.2018.11.003