Third-order nonlinear optical behavior and optical limiting properties of thulium-doped zinc tungstate crystal

Thulium-doped zinc tungstate (ZnWO₄: Tm) crystal is an important functional material, which has potential applications in the field of laser technology. However, the third-order nonlinear optical behavior and nonlinear optical limiting (NOL) properties of ZnWO₄: Tm crystal have rarely been investigated. In this study, we have successfully grown ZnWO₄ crystal doped with Tm³⁺ using the Czochralski method. We have measured the absorption, Raman, and X-ray diffraction spectra of the crystal, with absorption peaks corresponding to the energy transitions of Tm³⁺. Utilizing Z-scan technique at the wavelength of 1064 nm, we have determined the nonlinear absorption coefficients arising from two-photon absorption, the nonlinear refraction coefficients stemming from electronic Kerr effect, and the third-order nonlinear coefficients for the crystal. Furthermore, we have evaluated the NOL performance of the crystal by measuring its transmittance at three different thicknesses of 2, 4, and 6 mm. At the thickness of 6 mm, the crystal exhibits a maximum transmittance of 89.1% at low input fluence and a minimum transmittance of 54.2% at high input fluence. These experimental results suggest that the novel ZnWO₄: Tm crystal holds potential as a promising new material for NOL at 1064 nm.