Second harmonic generation in nonlinear disordered media

The efficient energy transfer in nonlinear parametric optical processes such as second harmonic generation (SHG) require phase-matching between the interacting waves. In order to fulfill this condition various methods have been developed, including the quasi-phase matching (QPM) technique which relies on the spatially periodic modulation of the medium´s nonlinear properties [1]. In case of ferroelectric crystals this is typically achieved by inducing periodic anti-parallel ferroelectric domain structure which leads to periodic reversal of the sign of quadratic nonlinearity.