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We report on the measurement of the electrooptic coefficient FJ| in proton exchanged LiNbO 3 waveguides. Using electrooptic prism (EOF) structures and waveguiding layer interferometers (WLI), we evaluated the electrooptic constants from the lateral Gaussian beam deflection and the measured phase shift, respectively, which are caused by external electric fields applied. For proton exchanged LiNbO 3 fabricated in 1 M% lithium enriched benzoic acid melt, we obtained a r 3 f value less than (2.0 + 0.3)· 10 ~6μιη/ν, significantly reduced in comparison with virgin LiNbO 3 . However, after strong annealing the electrooptic coefficient is almost re-established and arrives at (19.8 ± 1.5) · 10" 6 μπα/Υ.

A quantitative comparison of the photorefractive effect in annealed proton-exchanged channel waveguides in MgO-doped and congruent LiNbO(3) at the wavelengths of 633 and 830 nm is presented. An accurate measurement technique is described to measure the refractive-index change as a function of time and the guided mode intensity for different wavelengths. The results show that doping with 7% MgO reduces the photorefractive effect at a wavelength of lambda = 633 nm by 2 orders of magnitude. The photorefractive effect in the doped substrate shows only a weak dependence on the guided power. Doping with 4 mol.% MgO has only little effect on the photorefractive effect compared with that on the congruent material. A reduced photovoltaic current is responsible for the small photorefractive effect in the 7 mol. %-doped substrate.

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Photorefractive effects (PRE) in KTiOPO4 channel waveguides were studied at the wavelengths 0.633 and 0.83 μm. The 4 μm-wide waveguides were fabricated by Rb ion exchange on the z-face of the crystals and along the y axis. At 0.633 μm, crystals from one source showed conventional photorefractive response with a saturation index change Δn of 2×10−5, but samples from a different source were not photorefractive. Neither type of crystals displayed photorefractive behavior in response to 0.83 μm light at guided-wave power flow of 2.4×107 W/m2. Differences in bicrystal structure are suggested as a possible cause of differing PRE between the two samples. On crystals from the first source, the relaxation time of generating PRE is related to power flow of the irradiating beam. The relaxation time of PRE disappearance after stop irradiation is also related to power flow of the irradiating light.