Abstract-Theoretical Evaluation on Terahertz Source Generator from Ternary Metal Chalcogenides of PbM6Te10 (M = Ga, In)

Wendan Cheng, Chen-Sheng Lin, Hao Zhang, Guo-Liang Chai,

https://pubs.acs.org/doi/abs/10.1021/acs.jpcc.7b10972?journalCode=jpccck

We develop a new method to calculate nonlinear optical susceptibility, and give a definition of the extended figure of merit (EFOM) contributing from optical susceptibility, refractive index and absorptions to evaluate the material intrinsic property. The calculated phonon frequency determines the infrared absorption coefficient and transparent cutoff edge. We calculate the conversion efficiencies of terahertz source generating from chalcogenides PbM6Te10 (M = Ga, In), based on difference frequency generation of optical process in term of the EFOM and experiment parameters. The calculated terahertz light conversion efficiencies of PbGa6Te10 and PbIn6Te10 are in the order of 10-3 to 10-2 at low side of THz wavelengths, and the conversion efficiency of PnIn6Te10 is larger than that of PbGa6Te10 at the same conditions. A small terahertz wavelength and absorption coefficient, and large nonlinear susceptibility, i.e. a large EFOM will result in a large conversion efficiency. These studies give an indication that the chalcogenides with heavy element composites are the desired candidates as terahertz source generation. The present work will give contributions to evaluate and search new NLO materials as terahertz source generation.

Abstract-Theoretical Evaluation of Terahertz Sources Generating From Infrared Nonlinear Optical Materials SnGa4Q7 (Q = S , Se)

http://onlinelibrary.wiley.com/doi/10.1002/cphc.201601128/abstract

We have theoretically evaluated the integrate knowledge, which contribute to conversion efficiency, including the phonon, photon and electron properties of infrared nonlinear optical materials SnGa4Q7 (Q = S, Se) being as terahertz (THz) sources. Specially, we have developed a new formula to calculate susceptibility of difference frequency generation (DFG) optical process. By the characteristics of materials-self properties in the THz region, we find that a larger nonlinear susceptibility or a large figure of merit will result in a large efficiency of THz source by the comparisons between the findings of SnGa4Se7 and SnGa4S7 under the same experimental conditions, and the THz absorption will reduce the efficiency of THz source for the two materials of SnGa4Q7 (Q = S, Se). The efficiency of THz source also depends on the experimental conditions. A large crystal size, strong pump intensity and small THz wavelength will gain large efficiency of THz source based on DFG process. The efficiency is a comprehensive index to evaluate the THz source based on DFG process.