Wavelet-transform analysis for independent electro-optic control of multiple quasiphase-matched nonlinear interactions

Electro-optic control of quasiphase matching (QPM) conditions has been proven a useful technique in realisation of integrated nonlinear frequency conversion devices. Multiple nonlinear interactions may take place simultaneously in aperiodically poled (domain engineered) ferroelectric crystals. In this case it may be necessary to have the possibility of an independent control on any nonlinear interaction via the electro-optic effect. Whilst the Fourier transform provides the overall behaviour after the interacting waves have travelled throughout the whole domain structure, a window-transform analysis (like short time Fourier transform or wavelet-transform) reveals the spatial location of the crystal contribution to any particular interaction. This information is particularly useful if an independent control of individual interactions is pursued, based on the electro-optic effect.