The light propagation in channel waveguides, formed by silver ion-exchange in glass using dielectric and metallic masks, has been studied. It is shown that the variation of the mode interference pattern with formation process parameters can be predicted with good accuracy using a proposed model of diffusion coefficient dependence on diffusate concentration for solving the exchange equation and computing modes of the resulting refractive-index profile. It is found that the quasi-periodic nature of light propagation in the waveguides is determined by the interference of several lowest even waveguide modes and it is very dependent on the diffusion aperture width.

Properties of thin film waveguides obtained by using rf-sputtering from optical glasses on glass substrates of different composition have been studied. It is established that the character of the sputtered film properties dependence on the substrate composition is determined by the ratio of sputtered target and used substrate material mol-fractions. Optical heterogeneity of these films has been studied. The transition layer parameters dependence on the substrate composition is considered. The refractive index profile of films has been investigated by means of ellipsometry and WKB method. The film formation initial condition effect on its optical parameters is discussed.

A method for determining losses in single-mode channel waveguides has been developed which is capable of measuring simultaneously both propagation loss in a channel waveguide and coupling efficiency in a waveguide/single-mode fiber contact. The method was employed in determining losses in a single-mode Ti:LiNbO₃ channel waveguide.

The optical properties of Rb:KTP channel waveguides have been investigated. The increase in depth and refractive index have been measured and the anisotropy of the increase in index in such waveguides determined for several samples. In the experiment carried out on one of the waveguides no optical damage was observed up to power densities of 1 MW cm^-2 in the blue-green spectral region.

Various differential optical techniques have been developed to examine objects with minute topography and refractive-index variations. The differential phase optical microscope (DPOM) was shown to be capable of measuring variations in optical path length with the accuracy of about 0.2 nm. This technique seems to be very promising for the study of integrated optical components, where numerous waveguide structures usually have complicated refractive-index profiles and there is a well established need to know and control them properly. The differential approach is based on measurements of phase difference between two beams reflected from two adjacent points of a sample. It results in a high depth resolution but, on the other hand, the system response is fairly simple only for step-like structures and it should be treated carefully when measuring the arbitrary refractive-index profiles. The parametric method proposed recently uses the presumption about the shape of profile, the parameters of which are to be determined according to the differential phase measurements by the DPOM. Therefore, this method can be applied only if there is some previous information about the refractive-index profile of the structure to be examined.

Parameters of refractive-index profile, the birefringence value, and mode interference pattern of buried planar waveguides fabricated by proton irradiation with doses from 10¹⁴ to 10¹⁷ cm^-2 have been investigated experimentally. It has been shown that the Epsteyn model is a good approximation of waveguide refractive-index profile. The mechanical stress distribution in such waveguide layers has been studied by optical methods. A method for reconstructing the radiation induced defect distribution in the collision region has been proposed. The value of the proportionality factor in the refractive-index increment dependence on dose was determined more exactly on the basis of experimental data. Changes of the waveguide parameters dependent on the temperature of isochronous annealing also have been investigated.

Physical mechanisms, causing the change of optical properties of doped ferroelectric crystals, have been considered. The aspects which are essential for waveguide formation have been discussed. Among them are the possibility to predict optical properties with the help of a set of physical parameters, the reasons of the spread in optical characteristics of waveguides, etc.

The kinetic model of proton exchange in LiNbO₃, LiTaO₃ crystals is proposed. The model is based on the formalism of relative composing units, which enables the user to find the expressions for gradients of chemical potentials of diffused particles in the sublatticies of sites and intersites. The diffusion equations for hydrogen, lithium, and vacancies in sites are obtained. Their solutions with some values of self-diffusion coefficients allow us, for the first time, to explain the step-like concentration profile of hydrogen, the upper limit of its concentration, the asymmetry of hydrogen and lithium depth-distributions, and some other specific features of proton exchange process.

We have examined the effects of annealing in air at 350 to 550 degree(s)C on proton-exchanged waveguides in lithium niobate crystals. By making a complex analysis of the processes that take place during annealing, which included structural, waveguiding-optical, IR-spectroscopical, and thermogravimetric measurements, we were able to find the conditions under which the LiNb₃O₈ phase is formed in H:LiNbO₃ waveguides. A noticeable increase of LiNb₃O₈ begins at the moment the refractive index increment at the boundary of the initial proton-exchanged waveguide reaches the value (Delta) n_e equals 0.037. With further annealing, when the (Delta) n_e on the surface of the plate also becomes equal to 0.037, there begins the evaporation of Li₂O and intensive formation of LiNb₃O₈. The results presented enable one to understand why under certain conditions of annealing the optical losses in H:LiNbO₃ waveguides become greater, and to optimize the conditions of such annealing to produce high-quality waveguides.

By using x-ray diffraction from different crystallographic planes, we have found the crystal structure deformations in proton-exchanged and titanium-indiffused lithium niobate waveguides. We have calculated the appearing mechanical stresses and the contribution of the photoelastic effect to the changes in refractive indices. It is shown that the waveguides have biaxial structure.

A new method has been applied to form Cd_uZn₁-_uSe waveguides -- ion exchange in the melts of salts. The regularities and specific features of ion exchange processes Cd²⁺ yields Zn²⁺ in ZnSe powder and single crystal plates have been studied. Cd_uZn₁-_uSe solid solution obeys the model of regular solution. Temperature dependencies of equilibrium constant and interaction energy of strained and unstrained Cd_uZn₁-_uSe solid solutions have been defined. We proposed the model taking into account the role of lattice misfit-induced stresses and dislocations in the ion exchange equilibrium. The depth profiles of elements and the refractive-index profiles in the ion exchanged Cd:ZnSE waveguides were analyzed and temperature dependencies of the self-diffusion coefficients of Cd²⁺ and Zn²⁺ ions were determined.

In Rb:KTiOPO₄ and Cs:KTiOPO₄ waveguides, the dependence of the refractive index changes on the mole fraction of an admixture has been found to be of the form (Delta) n_i equals A_ic. In the Rb-doped case, the coefficients A_i are equal to A_x equals 0.030, A_y equals 0.026, and A_z equals 0.023, whereas these are 0.16, 0.13, and 0.10, respectively, for the Cs-doped case. Also found are the effective ion diffusion coefficients: from D_z+^* equals 0.11 (DOT) 10^-10 cm²/c to D_z-^* equals 0.17 (DOT) 10^-10 cm²/c in Rb:KTiOPO₄ layers at 400 degree(s)C and D_z^* equals 0.56 (DOT) 10^-11 cm²/c in Cs:KTiOPO₄ layers at 430 degree(s)C. In the waveguides under study, the dispersion of the refractive index increments within (lambda) equals 0.44 divided by 1.15 micrometers has been shown not to occur. The synthesis regimes for the formation of single-mode channel waveguides in Z-cut KTiOPO₄ have been calculated from the derived relations. Channel Rb:KTiOPO₄ waveguides, single-mode at (lambda) equals 1.15 micrometers , were obtained experimentally.

Theoretical and experimental results are presented on the characteristics of a Mach-Zehnder integrated-optic modulator with TM- and TE-polarized waves simultaneously excited at its input. It is established that under certain conditions the modulator linearity for a wave combination can be substantially increased above that obtained when light of one polarization is used. In the experiments, adjustment of light polarization at the modulator input with respect to the crystal axis ensured an optimal ratio of the wave intensities, so an increase of the linearity range (LR) from 69% to 92% was achieved and the dynamic range (DR) was improved from 75 dB to 87 dB.

In order to reduce nonlinear distortions inserted in an analog optical system by an integrated-optic modulator (IOM) of interferometric type, it is necessary that the modulator phase bias be at the middle of the linear section of the modulation characteristic (MC). In this paper, a technique is presented that allows us to tune phase bias and extinction ratio in a wide range by adjusting a single-mode fiber (SMF) at the modulator input. The technique is based on excitation of the symmetric and asymmetric modes of the input Y-junction. The ratio of their amplitudes is tuned by changing coupling conditions (adjustment of the fiber) that results in tuning of phases and intensities of the waves in the interferometer arms. The technique can be applied for a Mach-Zehnder modulator of the conventional scheme (with a single-mode input waveguide section), but to strengthen the effect, it is useful to modify the modulator geometry.

In this paper, a novel scheme of interference type modulator is proposed which ensures enhancement of linearity of the modulation characteristic (MC) by adding sinusoidal MCs. These characteristics correspond to the waves that appeared as a result of multiple reflections from the waveguide faces.

New chirped-toothed electrodes with triangular or trapezoidal edges are invented for Z-cut LiNbO₃ travelling-wave integrated-optic channel modulators. Such electrodes produce sweeped-frequency sinusoidally oscillating spatial dependencies of the local electro-optic interaction efficiency upon the coordinate along the direction of wave propagation. These dependencies are obtained for lossless electrodes by the reverse Fourier transform implying the desirable uniform rectangular magnitude-frequency-response and quadratic phase-frequency-response of the designed modulator. The invented electrodes ensure either equiefficient bandwith broadening or modulation efficiency increase in the fixed frequency band depending on the implied frequency response. The influence of the frequency dependent rf losses is corrected by an appropriate amplitude modification of the electro-optic interaction dependence for initially lossless electrodes. For example, two electrode structures (1 cm and 7.5 mm long) are designed for the broadband (up to 160 GHz) and bandpass (from 80 GHz up to 160 GHz) modulators. The computed magnitude frequency responses show perfect uniformity in the frequency band taking into account the influence of the frequency dependent rf losses of 1 - 2 dB (DOT) cm^-1 (DOT) GHz^-1/2.

Acousto-optic (AO) interaction in waveguide structures based on GaAlAs solid alloys has been investigated. A full set of the elastic and photoelastic constants of Ga_1-xAl_xAs was estimated. Dependencies of the AO interaction efficiency on the surface acoustic wave (SAW) frequency, waveguide parameters, and optical wavelength were obtained from the exact solution of SAW propagation in a layered structure. Results of experimental investigations on a GaAlAs-waveguide at the wavelengths of gallium arsenide ((lambda) ₀ equals 0.88 micrometers ) and gellium-neon ((lambda) ₀ equals 1.15 micrometers ) lasers in the frequency range of 100 - 500 MHz are presented.

We propose the use of KTP-based waveguides for all-optical switching. The passing of subnanosecond light pulses through an Rb:KTP nonlinear directional coupler is investigated. The nonlinear switching of 40% of light power from the one channel to the other is observed at 5 kW input power.

For the first time the excitation of surface acoustic waves (SAWs) by means of interdigital transducers has been realized in an Rb:KTP crystal. The SAW speed of 3.9 km/s and the insertion loss of 29 dB were measured at the frequency of 240 MHz.

The theoretical analysis of operation of an integrated electro-optic Bragg processor for digital-to-analog conversion and scalar multiplication of vectors is presented on the basis of the two-wave two-dimensional theory of Bragg diffraction. It is shown that the accuracy of these operations is determined by the geometry parameter of an individual Bragg cell. The relevant results of the experimental study of the processor fabricated utilizing a planar Ti-diffused waveguide in LiNbO₃ are reported.

Two-dimensional problems of the calculation of planar electrode systems are considered. A rigorous solution is found in analytic form for the quasistatic electrodynamic problem of planar systems with an arbitrary number of parallel infinite thin electrodes placed on the interface of two arbitrarily oriented conducting single crystals. On this basis transition processes connected with a spatial charge excitation in anisotropic media are analyzed. A numerical method of solving the electrostatic problem for planar electrodes with a buffer layer is developed. The established analytic solutions for infinitely thin electrodes are used for approximate solutions design in the case of realistic finite thickness electrodes and in the case of the buffer layer presence.

This paper is devoted to the description of the basic properties of the collinear acousto-optic (AO) interaction in planar waveguides and its applications recently developed for different multichannel AO devices performing light deflection, spectrum analysis, spectrum multiplexing and demultiplexing, etc.

The problem of the waveguided light energy loss, due to irregularities of the surfaces, was raised in the very first works on planar optics. Later, the light scattering on irregularities of thin-film waveguides (TW) was discussed by a number of authors. There are two approaches to the problem: attenuation coefficient, and scattering diagram (SD), etc., -- direct problem and characterization of surface roughness statistical parameters with the help of recorded scattering diagram -- inverse problem. Here we discuss the works performed at the Department of Radiophysics of the People's Friendship University since 1963, mainly those that deal with the light scattering on irregularities of TW and the characterization of the surface roughness.