Second-order nonlinear effects in asymmetric quantum-well structures

Abstract

The expression for second-order optical susceptibility based on band-to-band and intraband transitions in various asymmetric multiple-quantum-well structures is derived. The analogy with organic nonlinear materials is shown. The dependence of the second-harmonic coefficient and Pockels coefficient on well geometry, band offsets, and other material parameters is studied. The nonlinear and electro-optic coefficients of GaAs-${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As asymmetric quantum-well systems are estimated to be in the range of most conventional nonlinear materials, while for proposed ZnSe-GaAs heterostructures these coefficients are found to be substantially larger than in conventional materials. Some practical applications of asymmetric quantum-well systems are discussed, including novel methods of phase matching. The case for engineering of novel nonlinear materials is made.