Abstract

We present a detailed investigation on thickness-dependent third-order (χ(3)) nonlinear optical properties of RF-sputtered WSe₂ thin-films using ultrashort pulses centered at different excitation wavelengths. The single-beam Z-scan based investigation in the visible spectrum reveals the prominent role of Pauli-blocking towards inducing saturable absorption or optical limiting in WSe₂ thin-films of various thicknesses. The study also explores the dispersion in third-order nonlinear susceptibility (χ(3)) in WSe₂ thin films. Interestingly, WSe₂ thin-films of any thickness exhibit a self-focusing effect depicting a positive nonlinear refractive index (n2 > 0). The frequency-dependent nonlinear absorption (β) bear distinct correlations with the bandgap of the films which is also investigated through density-functional-theory (DFT) based simulations. The alteration in bandstructure is primarily due to the Se-deficiency induced defect bands in WSe₂ thin-films which has discernible impact on the optical limiting characteristics.

Abstract

We present a detailed investigation on thickness-dependent third-order (χ(3)) nonlinear optical properties of RF-sputtered WSe₂ thin-films using ultrashort pulses centered at different excitation wavelengths. The single-beam Z-scan based investigation in the visible spectrum reveals the prominent role of Pauli-blocking towards inducing saturable absorption or optical limiting in WSe₂ thin-films of various thicknesses. The study also explores the dispersion in third-order nonlinear susceptibility (χ(3)) in WSe₂ thin films. Interestingly, WSe₂ thin-films of any thickness exhibit a self-focusing effect depicting a positive nonlinear refractive index (n2 > 0). The frequency-dependent nonlinear absorption (β) bear distinct correlations with the bandgap of the films which is also investigated through density-functional-theory (DFT) based simulations. The alteration in bandstructure is primarily due to the Se-deficiency induced defect bands in WSe₂ thin-films which has discernible impact on the optical limiting characteristics.

Abstract

We present a detailed investigation on thickness-dependent third-order (χ(3)) nonlinear optical properties of RF-sputtered WSe₂ thin-films using ultrashort pulses centered at different excitation wavelengths. The single-beam Z-scan based investigation in the visible spectrum reveals the prominent role of Pauli-blocking towards inducing saturable absorption or optical limiting in WSe₂ thin-films of various thicknesses. The study also explores the dispersion in third-order nonlinear susceptibility (χ(3)) in WSe₂ thin films. Interestingly, WSe₂ thin-films of any thickness exhibit a self-focusing effect depicting a positive nonlinear refractive index (n2 > 0). The frequency-dependent nonlinear absorption (β) bear distinct correlations with the bandgap of the films which is also investigated through density-functional-theory (DFT) based simulations. The alteration in bandstructure is primarily due to the Se-deficiency induced defect bands in WSe₂ thin-films which has discernible impact on the optical limiting characteristics.

Abstract

We present a detailed investigation on thickness-dependent third-order (χ(3)) nonlinear optical properties of RF-sputtered WSe₂ thin-films using ultrashort pulses centered at different excitation wavelengths. The single-beam Z-scan based investigation in the visible spectrum reveals the prominent role of Pauli-blocking towards inducing saturable absorption or optical limiting in WSe₂ thin-films of various thicknesses. The study also explores the dispersion in third-order nonlinear susceptibility (χ(3)) in WSe₂ thin films. Interestingly, WSe₂ thin-films of any thickness exhibit a self-focusing effect depicting a positive nonlinear refractive index (n2 > 0). The frequency-dependent nonlinear absorption (β) bear distinct correlations with the bandgap of the films which is also investigated through density-functional-theory (DFT) based simulations. The alteration in bandstructure is primarily due to the Se-deficiency induced defect bands in WSe₂ thin-films which has discernible impact on the optical limiting characteristics.