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We have successfully demonstrated a low-driving-voltage electro-optic (EO) modulator using newly developed KTa1-x Nb x O3 (KTN) buried waveguides. We prepared high-quality and large KTN crystals. The crystals exhibited a large quadratic EO coefficient of 4.8×10-15 m2/V2 at 1.55 µm. The KTN crystals also exhibited a very large linear EO effect, for example 600 pm/V at a biased potential of 60 V/mm, which is twenty times larger than the r 33 of LiNbO3. The waveguide layers for the core and cladding were formed by liquid phase epitaxy techniques on the KTN crystals. The propagation loss was less than 0.5 dB/cm and the polarization dependent loss was less than 0.1 dB/cm. The EO modulators had a low V π of <2.5 V (4.0-V biased potential, l=6 mm) and a fast response of 3 GHz.

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An epitaxially grown ytterbium-doped gadolinium gallium garnet (Yb:GGG) buried channel waveguide laser is prepared on an yttrium substituted GGG substrate (Y:GGG). The effective light guiding structure is obtained as a result of the difference of refractive indices of Yb:GGG and Y:GGG. The Yb:GGG waveguide exhibits single-mode 1.025 μm lasing operation at room temperature. The incident threshold and slope efficiency of the 5-mm-long waveguide laser when pumped at 0.941 μm are 80 mW and 13.4%, respectively.

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