Dislocation parity effects in crystals with quadratic nonlinear response.

The effect of edge topological dislocations on the phase matching spectrum of quadratic nonlinear photonic crystals was studied theoretically and experimentally. We have found that the parity of the dislocation's topological charge governs the transfer of energy between an input wave and its second harmonic. A dislocation with an odd topological charge nulls the efficiency of the otherwise optimal phase matched wavelength, whereas high conversion is now achieved at new wavelengths that exhibited low efficiency without the dislocation. However, when the topological charge is an even number, the dislocation has a negligible effect on the efficiency curve. This effect is observed in periodically poled crystals having a single peak in the phase matching spectrum, as well as in phase-reversed and quasiperiodic nonlinear photonic crystals that are characterized by multiple efficiency peaks, where a dimple is imprinted on each spectral peak.