Dynamic linear electro-optic frequency dependence in PMN-32%PT and PZN-8%PT for RF microwave photonics

The electrooptic effect (at lambda = 633nm) in both PMN-32%PT and PZN-8%PT relaxor ferroelectric single crystals was investigated as a function of small signal modulation frequencies. Piezo-resonance measurements were also conducted to examine piezooptic coupling in these materials for selected resonance modes to observe the influence of piezoelectric activity on the electro-optic behavior. The electrooptic rC coefficient in PMN-32PT and PZN-8%PT crystals were found to have strong frequency dependence at frequencies below 100s Hz apparently due to space charge effects. Anomalous electrooptic properties near piezoelectric resonance frequencies are reported to be attributed to a synchronization of the low frequency piezoelectric resonance and high frequency transverse lattice vibrations near 4th harmonics.; Also reported is enhanced electrooptic properties near piezoelectric resonant frequencies that may be attributed to synchronization of the low frequency fundamental modes and up to their 5th order harmonics accompanied by nonlinear extrinsic activity in the form of lateral domain region motion. A constructive interaction with overlapping high order piezoelectric and electrooptic resonances can be engineered, using PMN-32%PT rhombohedral and PZN-8%PT crystals as an example, so that a small signal (.25V/mm) amplified electro-optic detector in the RF frequency region may be envisaged.