Third-order nonlinear optical susceptibility of wide-bandgap nitrides

Abstract

We calculate the third-order nonlinear optical susceptibility of III - V nitride compounds by adopting a linear combination of hybrids method which we have developed. We have constructed a basis set for the valence bands which is a linear combination of hybrids forming a bond in which their relative phase factors have been properly included. We have also constructed conduction-band states which are orthogonal to the valence-band states. We have used these basis functions in the expression for the non-dispersive part of . We have made an average energy-gap ansatz for the energy-gap denominator occurring in the expression for . We have used the Hall - Weaire and Thorpe approximation to calculate the matrix elements between different hybrids. We obtain in a tractable form in terms of matrix elements between intrasite hybrids and between hybrids of adjacent sites forming a bond. We have calculated of BN, AlN, GaN and InN and it would be interesting to compare our results with experimental data, when available.