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Channel waveguides have been produced in LiNbO3, LiTaO3, and BaTiO3 ferroelectric crystals by depositing thick SiO2 films at an elevated temperature and patterning them by reactive ion etching. The static strain resulting from the large thermal expansion mismatch between the substrate and film causes a localized increase in the refractive index via the strain-optic effect. In addition, an electro-optic contribution to the index increase is believed to result from a surface charge distribution which compensates the electric field due to the piezoelectric effect. Single-mode waveguides at a wavelength of 0.633 μm for both polarizations have been produced in x-cut LiNbO3, with losses of 0.8 dB/cm for TE polarization and 0.9 dB/cm for TM polarization. The 11-μm-wide channel waveguides were formed by a z-axis strain induced by a 2.8-μm-thick SiO2 film deposited at 300 °C. Electro-optic modulation was also demonstrated in these waveguides. Guiding for both polarizations was also observed in LiTaO3 and BaTiO3 channel waveguides at 0.83 μm wavelength.

Mobility data for GaP in the temperature range 200–550 K as a function of impurity concentration are presented. The data were determined from sheet Hall coefficient and resistivity measurements obtained using the van der Pauw method. The results are given for a wide range of concentrations ranging from unintentionally doped to degenerately doped conditions. The maximum values of the electron and hole mobilities at room temperature were found to be 160 and 135 cm2/Vs, respectively. The observed average temperature dependence of the mobility is T−1.7 for electrons and T−2.3 for holes.

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Low-loss optical waveguides have been produced in z-cut Sr0.6Ba0.4Nb2O6 (SBN:60) and electro-optic modulation has been demonstrated at a wavelength of 1.3 μm. The refractive index increase responsible for waveguiding results from a strain produced by a SiO2 film which has been deposited on the surface of the substrate at 320 °C. The waveguides are formed in the crystal by dry etching of channels in the strain film. The resulting optical waveguides support both polarizations. Propagation loss values of 0.7 dB/cm for TM polarization and 1.6 dB/cm for TE polarization were measured. Electro-optic modulation up to 22 MHz was performed on repoled samples using coplanar electrodes.

Characterization of bulk single crystals and optical waveguides in Ba1−xSrxTiyNb2−yO6 (BSTN) indicate it to be a promising new ferroelectric material for electrooptic devices. The electro-optic coefficient r33 is measured to be 218±12 pm/V, a factor of 7 greater than LiNbO3. Data on refractive indices, dielectric constant, and Curie temperature Tc in bulk samples are also presented. Strain-induced waveguides in Z-cut samples exhibited low losses (1.8 dB/cm for TM polarization and 2.5 dB/cm for TE polarization) at a wavelength of 1.3 μm. Electro-optic modulation was demonstrated in these waveguides to frequencies ≳100 MHz. A ‘‘self-poling’’ effect was found, whereby strong electro-optic modulation is observed in the strain waveguides without repoling the crystal after processing at temperatures far above Tc.

New designs for acousto-optic tunable filters and electro-optic tunable filters with the Mach-Zehnder configuration are proposed. The new designs differ from conventional designs in three respects: (1) polarizing beam splitters are not required, (2) the optical path difference for the waveguides between the beam splitters is a half-wavelength, and (3) the relative positions of the polarization coupling regions in the two waveguides are displaced in the propagation direction by half of the spatial period of the perturbation responsible for the coupling. Because the new designs provide an additional degree of freedom in achieving the required beam-splitter performance, they are expected to be much easier to fabricate than conventional filter designs with polarizing beam splitters.

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