Piezoelectric resonance enhanced optical transmission at microwave frequencies

Both the intrinsic and secondary contributions to the electrooptic (EO) coefficients in ferroelectric PMN-PT, PZNPT, and (Sr,Ba)Nb2O6 crystals, were studied. At low frequencies space charge and acousto-optic coupling effects dominate the apparent EO effect measured, which however decreases steeply upon increasing of frequency. At certain frequencies relevant to piezoelectric resonance frequencies of given mode, it is found that EO coefficient and the optical transmission are greatly enhanced. Such enhancement is explained qualitatively using the theoretical model of transverse optical phonons of lattice wave. When being coherent in scale with crystal dimensions, the displacive current created by transverse optical phonons could enhance the EO coefficient at the given frequency. The implication of the lattice vibration EO amplification and the feasibility of engineering single crystal resonators as detectors or modulators in selected frequencies as microwave photonic devices are explored and discussed.