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An integrated optics spectrum analyzer based on using the linear electrooptic effect was theoretically investigated earlier. This spectrum analyzer performs Fourier analysis of sampled electronic signals, where each voltage sample is fed to an electrode of a metal electrode array. The electrode array acts as a spatial light modulator, and the diffracted light field is focused on a detector array. The intensity values at the detector elements represent a weighted discrete Fourier transform of the voltage values on the electrodes. The first experimental results to verify the principle of operation of the device are now reported and compared with theory. The prism coupling technique has been used to investigate the influence of an electrode array with voltages on a collimated beam in a LiNbO_3 waveguide. The voltage distributions analyzed correspond to a square wave function and rect functions. The theory has also been extended, and some pertinent signal processing properties of the device are discussed.

Refractive-index profiles and diffusion parameters for planar and channel waveguides fabricated in magnesium-doped lithium niobate by titanium indiffusion are investigated. The diffusion constant was found to be 5.5 × 10^−17 m^2/sec at 1050°C, which is approximately 3.5 times lower than for comparable undoped lithium niobate. An enhanced lateral diffusion was observed, which could not be unambiguously described by using the diffusion model commonly adopted for Ti:LiNbO_3 channel guides. The wavelength dispersion for the index increase was found to be the same as for undoped lithium niobate. The ordinary index increase was found to vary approximately linearly with the titanium concentration, which is in strong contrast to the case of undoped lithium niobate. The results obtained have important implications for the design of waveguides for nonlinear optical applications as second-harmonic generation.

Second-harmonic generation (SHG) in channel waveguides fabricated by titanium diffusion into MgO-doped lithium niobate is studied. A conversion efficiency for SHG of 2.4%/W has been obtained for a 16-mm-long waveguide by using a Nd:YAG laser as pump source. The conversion efficiency is lower than the theoretical prediction. This difference is attributed to inhomogeneities along the waveguide. The channel waveguides used carried several modes at the second-harmonic wavelength; those modes, phase matched above room temperature (~80°C), showed substantially lower sensitivity for photorefractive damage than others phase matched at room temperature.