Guided-wave electrooptic devices utilizing static strain induced effects in ferroelectrics

The static strain optic (SSO) effect has been used in different ferroelectric substrate materials as a means of producing channel waveguides and various integrated optic devices. The static strain results from the large thermal expansion mismatch between the substrate and a thick film of SiO2 that is deposited on the surface at an elevated temperature and patterned at room temperature. Record low loss channel waveguides have been produced in tungsten bronze substrates SBN and BSTN, which have electrotrooptic coefficients similar to an order of magnitude greater than LiNbO3. GHz-bandwidth electrooptic modulation in the tungsten bronzes was obtained without repoling the crystal after processing at temperatures far above. T-c. In another application of the SSO effect, phase-matched polarization coupling has been used in an electrooptically tunable TE-TM mode converter and a channel dropping filter in LiTaO3.