Quadratic Nonlinear Optical Coefficient of AlxGai-xAs Thin Film

Recently there has been considerable interest in surface-emitting second-harmonic (SH) generators fabricated from the AlxGa1-xAs system.1,2) No systematic data are available, however, on the d coefficients of AlxGa1-xAs1,3,4) A major reason for this is that many interesting semiconductors, including AlxGa1-xAs, are obtainable only in the form of a thin epitaxial layer. Furthermore, the substrate is often absorptive at SH frequencies. We have developed a new method for characterizing the optical nonlinearity of such thin-film materials on the basis of the method of reflected harmonics.5) The new method has been applied to the determination of the coefficient d14 of AlxGa1-xAs as a function of x, the AlAs composition of the alloy semiconductor.