Tuning linear and nonlinear optical properties of wurtzite GaN byc-axial stress

Abstract

We study the linear and nonlinear optical properties of wurtzite GaN under c-axial stress field, using density functional theory calculations. The fully structural optimization at each c-axial strain was performed. The calculated dielectric functions show that tensile c-axial strain effectively improves the linear optical efficiency, especially for the band-edge transitions, and significantly increase the mobility of electrons in the conduction band. Second-order nonlinear optical susceptibilities show that the tensile c-axial strain will enhance the zero-and low-frequency nonlinear responses of GaN. The enhancement of the nonlinear optical property is explained by the reduction of the polarization of wurtzite GaN under tensile c-axial strains. Based on these findings, we propose a method for improving the electrical and optical properties of the crystal through imposing appropriate stress on the high symmetry crystalline directions.

Large second-harmonic generation and linear electro-optic effect in trigonal selenium and tellurium

“…It is clear from Fig. 7(b) that the spectrum of the absolute value of χ (2) xxx (−2ω, ω, ω) shows a broad plateau from 1.34 eV to 3.44 eV and reaches the maximum of 1.85×10 −6 esu at 1.7 eV which is a few times larger than that of GaN [6,7], a widely used NLO semiconductor.…”

“…Note that the r(0) and χ (2) (0, 0, 0) are listed in the units of SI pm/V unit and 1 pm/V (= 3 4π × 10 −8 esu). Interestingly, Table VII shows that tellurium exhibits large static secondorder NLO susceptibility, especially χ (2) xyz (0), which is up to 100 times larger than that of GaN in both zinc-blende and wurtzite structure [6,7]. Furthermore, for both materials, the static second-order NLO susceptibility exhibits strong anisotropy.…”

“…The phenomenon is explained by the fact that the two materials are helical chains along the c-axis and possess a high degree of anisotropy. In particular, the absolute value of second-order NLO susceptibility χ (2) xxx of tellurium is as high as 8.69×10 −6 esu at 0.94 eV, which is nearly sixteen times larger than that of GaN [6,7]. This suggests that tellurium would be a superior NLO material and has potential application in NLO and LEO optical devices such as frequency conversion, optical switching, second-harmonic generation, optical modulation and sensing devices.…”

Variation of second-order piezoelectric coefficients with respect to a finite strain measure

“…Also, theoretical calculations have predicted the nonlinear behaviour of such crystals, see e.g. Shimada et al (1998), Gavrilenko & Wu (2000), Ambacher et al (2002), Cai & Guo (2009), Clayton (2010, Pal et al (2011Pal et al ( , 2012, Beya-Wakata et al (2011), Prodhomme et al (2013). Linear piezoelectric parameters of the material can be determined by the use of many, well established approaches, while formulation and measurements of higher-order piezoelectric coefficients (elastostriction and electrostriction) are not clearly presented in the literature.…”

Strain-induced improvements on linear and nonlinear optical properties of SrB4O7 crystal

“…1(a)]. Thus, it is reasonable to apply the directional external stress in order to introduce the configurational as well as optical anisotropy, which have already been successfully done in tuning magnetism, 12 ferro-electricity 13 and optical properties [14][15][16][17] of many other materials. The first-principles density functional theory (DFT) methods implemented in CASTEP package are employed.…”