Tunable guided‐wave optical polarization converters in lithium tantalate
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Tunable guided-wave TE↔TM mode converters have been produced in LiTaO3using strain-induced polarization mode coupling. The waveguides are formed by Zn diffusion from the vapor phase. Phase matched coupling is obtained by depositing a thick SiO2film at an elevated temperature and delineating a spatially periodic pattern in the film at room temperature. The static shear strain resulting from the large thermal expansion mismatch between the substrate and film causes an off-diagonal change in the refractive index via the strain-optic effect and promotes TE↔TM coupling. Polarization conversion in excess of 98% was achieved at a wavelength of 627 nm in X-cut LiTaO3. The conversion efficiency is highly wavelength selective, with a spectral width of 7.3 nm in the 5.4 mm long device. Thermal and electro-optic tuning of the center wavelength was demonstrated.
author list (cited authors)
Tang, Z., Eknoyan, O., Taylor, H. F., & Swenson, V. P.