Ab initio calculated frequency-dependent nonlinear optical properties on CsGeBr3

L. C. Tang; Y. C. Chang; J. Y. Huang; C. S. Chang

doi:10.1117/12.681410

7 September 2006 Ab initio calculated frequency-dependent nonlinear optical properties on CsGeBr3

L. C. Tang, Y. C. Chang, J. Y. Huang, C. S. Chang

Author Affiliations +

Proceedings Volume 6294, Infrared and Photoelectronic Imagers and Detector Devices II; 62940J (2006) https://doi.org/10.1117/12.681410
Event: SPIE Optics + Photonics, 2006, San Diego, California, United States

Abstract

A systematic first-principles calculation of the linear and second-order optical susceptibilities as functions of frequency for CsGeBr₃ is presented. Specifically, we study the relation between the structural properties and the optical responses. Three structural deformation factors, Δα, d_Ge, d_X are used to express the degree of distortion from the ideal perovskite structure in bond angle, Ge position, and anion position, respectively. Based on our first-Principles studies, we find that Δα and d_Ge increase, while d_X decreases as we substitute the halogen ion from Cl to Br and then to I. The dielectric function and the second harmonic generation coefficient are also found to increase with increasing Δα and d_Ge. Our calculation indicates that the direct bandgap, E_g, of CsGeX₃ occurs at the R-point for all three compounds, and its magnitude decreases as Δα and d_Ge increase (i.e. E_g(CsGeI₃) < E_g(CsGeBr₃) < E_g(CsGeCl₃)). Our partial density of states (PDOS) analysis reveals that the valence band maximun (VBM) and conduction band minimum (CBM) are mainly associated with the p-orbitals of Germanium. Interband and intraband analysed results for (formula available in manuscript) in C_sG_eBr₃ can be separated into two main groups of peaks. One was contributed from the magnitude electronic bandgap; the other part was recognized to be attribution from the distortional structural factors. The magnitudes of (formula available in manuscript) were in the same manner with some reported experiment near the band gap.

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L. C. Tang, Y. C. Chang, J. Y. Huang, and C. S. Chang "Ab initio calculated frequency-dependent nonlinear optical properties on CsGeBr3", Proc. SPIE 6294, Infrared and Photoelectronic Imagers and Detector Devices II, 62940J (7 September 2006); https://doi.org/10.1117/12.681410

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