Materials Science and Engineering

Biography

Biography: Wen-Dan Cheng

Abstract

Terahertz (THz) wave is the explosion of applications requirements, especially in the fields of security and biomedicine. However, there are still delays in a widespread use of THz technology due to the scarcity of reliable, simple use sources produced on a large scale. New mid/far infrared nonlinear optical crystals SnGa₄Q₇ (Q = S, Se) can be used to design laser sources of THz wave by difference frequency generation (DFG) process. In order to simulate the output THz light, we have calculated the conversion efficiencies of THz source, which are relative with the cutoff edge of transparent infrared spectrum, absorption coefficient of THz light, and figure of merit, based on the DFG process of infrared nonlinear optical materials SnGa₄Q₇ (Q = S, Se). The calculated phonon dispersions and phonon band densities are employed to determine the transparent cutoff edge of infrared spectrum. The calculated infrared intensities are used to derive the absorption coefficients of THz wave. The calculated nonlinear optical parameters and linear refractive indices are used to determine the figure of merit. The obtained results show that the THz conversion efficient of SnGa₄Se₇ is much larger than that of SnGa₄S₇ under the same experimental conditions, and the THz absorption significantly reduce the conversion efficiency of THz source for the materials of SnGa₄Q₇ (Q = S, Se). We should choose more wide transparent material in mid/far infrared zone or avoid the THz absorption band of material, and choose a large figure of merit material in designing THz source based on DFG process.