Dmitrii K. Tagantsev

Optical limiting behavior of a glass–ceramic containing sodium niobate crystallites

The nonlinear absorption properties of a glass–ceramic containing ferroelectric sodium niobate (NaNbO3) crystallites were investigated. Two- and three-photon absorption coefficients were determined using nanosecond pulsed lasers. The optical power-limiting performance for light beams at 1064 and 532 nm was dependent on the volume fraction of NaNbO3 crystallites formed during the heat-treatment process.

Picosecond Z-scan measurements on a glass-ceramic containing sodium niobate nanocrystals

Abstract The third-order nonlinearity of a glass-ceramic containing sodium niobate (NaNbO 3 ) nanocrystals was studied using the Z -scan technique. The measurements were performed at 532 nm with 70-ps pulses at 5 Hz. Two-photon absorption coefficients and light-induced refractive index changes were determined. The results show dependence of the nonlinear parameters on the volume fraction of NaNbO 3 crystallites.

A Highly Sensitive Technique for Measurements of the Kerr Electrooptic Coefficient in Glasses and Glass Ceramics

A technique for measuring the Kerr electrooptic coefficient in glassy optical materials and the corresponding laboratory setup are described. The technique proposed, which is based on the application of an alternating voltage of a sound frequency to the samples under characterization, ensures the compensation of the initial birefringence of the samples and shows a high sensitivity (Bmin = 10–17 m/V2 and Δnmin = 0.8 × 10–8) at moderate requirements for the optical quality of the samples. The comparative measurement method, the unaltered opto-mechanical part of the setup, and the minimum number of the measured parameters make it possible to eliminate a number of sources of errors and to offer the prospect for developing an automated setup.

Near-infrared nonlinear properties of a glass–ceramic containing sodium niobate nanocrystals

We have investigated the third-order nonlinear optical response of a niobic–silicate glass–ceramic containing sodium niobate (NaNbO3) nanocrystals using picosecond Z-scan and femtosecond optical Kerr gate techniques at 1064 and 800 nm, respectively. The results show a large dependence of the nonlinear refractive index (n2) on the volume fraction occupied by NaNbO3 crystallites. Nonlinear absorption is negligible for all samples and the response time of the nonlinearity was shorter than 100 fs demonstrating that this material is a promising candidate for ultrafast optical switching.

Graded index objective with a spherical end for endoscopy

A number of problems connected with producing the graded-index micro-objective with a spherical end for medical endoscopy, including the optical material and the mathematical modeling of optical and physico-chemical processes, have been considered in view of the technology of producing those objectives.

Niobium phosphate glasses doped with rare earths

Er- and Sm-doped sodium-niobium phosphate glasses have been produced by melting technique. Their optical and spectroscopic properties have been fully characterized. Fluorescence lifetimes of the metastable states of Er3+ and Sm3+ ions are long enough to make these glasses suitable to be used in optical amplification devices. Waveguides have been produced by diluted Ag+/Na+ ion exchange and their properties are also described.

GRIN elements in the interference method of glass index measurement

A new interference method for measurement of the refractive index of glass has been developed. The method is based on the Mach-Zehnder interferometry and GRIN elements are used for a scale of refractive index. Cone, pyramid or wedge elements are privileged in this method. Both the object under study and GRIN elements are placed in an oil immersion container, then oil is heated until the specimen becomes invisible. For such a situation the interference fringes produced by the GRIN standard are analyzed. The accuracy of refractive index measurements is equal to +/- 0.00001.

New fabrication technology of micro-objectives for endoscopy

Technological possibilities of making wide-angle micro-objectives for endoscopes out of separate modules with different refractive indexes (RI) have been considered and the corresponding investigation of optical calculations has been done. Aspherical surfaces in modules was achieved without any mechanical treatment.

Nonlinear refractive behavior of a transparent glass-ceramic containing NaNbO/sub 3/ nanocrystals in the infrared

The nonlinear optical behavior of a glass-ceramic containing sodium niobate (NaNbO/sub 3/) nanocrystals (GC-SNN) was studied in recent experiments where the third-order susceptibility, /spl chi//sup (3)/, at 532 nm was measured using nanosecond power limiting and picosecond Z-scan techniques. It was shown that the presence of NaNbO/sub 3/ nanocrystals influences the magnitude of the nonlinear (two-photon) absorption coefficient (/spl alpha//sub 2/) and the nonlinear refractive index (n/sub 2/) of the material. Here we extended our previous studies probing /spl chi//sup (3)/ at wavelengths where nonlinear absorption contributions are negligible.

Origin of electrooptical sensitivity of glasses

A niobium-lithium-silicate glass demonstrating a record Kerr coefficient (266•10-16 m/V2) has been formed, and transparent glass-ceramics demonstrating Kerr coefficients exceeding 6000•10-16 m/V2 has been elaborated. A conception of the origin of electrooptical sensitivity of glasses is developed. It supposes that the fluctuation microinhomogeneities peculiar to as-prepared glasses are the regions with exact crystalline symmetry, and that just those regions are the pre-nuclei of the crystallites, which form in glass-ceramics in heat treatment. Having the composition and the symmetry of electrooptical ferroelectric crystal, these regions appear to condition high Kerr sensitivities of both the glasses and the glass-ceramics formed from these glasses.