Types of acousto-optic interactions between acoustic and circularly polarized optical waves:case of Pb5Ge3O11 crystals.

In the present work, we analyze acousto-optic (AO) interactions between acoustic waves (AW) and circularly polarized optical eigenwaves in gyrotropic crystals. We find that the AO diffraction of circularly polarized eigenwaves can be divided into six different interaction types. Contrary to the AO interactions analyzed earlier for the case of linearly polarized optical eigenwaves, we distinguish three isotropic interaction types and three anisotropic ones. Moreover, unlike the isotropic AO interactions of linearly polarized eigenwaves of no-no and ne-ne interaction types, the effective elasto-optic coefficient (EEC) in the case of interactions between circularly polarized eigenwaves does not depend on the sign of an incident circular optical wave. The anisotropy of the EEC and AO figure of merit is analyzed for a particular case of lead germanate crystals, Pb5Ge3O11. We demonstrate that the maximal AO figures of merit are achieved for type I isotropic diffraction at the quasi-longitudinal AW. Our calculations are confirmed by the experimental data obtained for the EEC using the Dixon-Cohen method. The experiment is concerned with the AO interactions of circular eigenwaves in Pb5Ge3O11.

Electro-optically induced topological reactions of optical indicatrix orientation and polarization state defects.

We have studied the behavior of topological defects (TDs) of the optical indicatrix orientation and polarization state, which appear when a divergent optical beam propagates through LiNbO3 crystals under an external electric field. We have found that the topological reaction of the splitting of a central TD of optical indicatrix orientation, which occurs under the electric field EX, proceeds according to a scheme 1=1/2+1/2. This reaction splits a doubly charged optical vortex into two singly charged vortices. An increase in the electric field strength leads to angular displacement of the optical vortices, thus making it possible to operate spatial positions of the optical vortices via a Pockels effect. We have found that the lateral TDs with the strengths ±½ represent the defects of the polarization state and are not caused by defects of optical indicatrix orientation. They form topological dipoles and generate optical vortices. These topological dipoles undergo no topological reactions in the external electric field.

Efficient acousto-optic crystal, TlInS2: acoustic and elastic anisotropy.

We have studied experimentally the acoustic wave velocities for TlInS2 crystals and determined all components of their elastic stiffness and compliance tensors. It has been found that TlInS2 reveals small elastic anisotropy with respect to normal mechanical stresses. The compliance components S44 and S55 are very large, thus suggesting that the TlInS2 crystals are extremely compliant to the shear stresses in the cleavage plane. We have also revealed that the velocities of some of the quasi-transverse waves are very low (∼725 m/s), leading to extremely high acousto-optic figures of merit (∼2200-9000×10-15 s3/kg). This implies that the crystals under study can prove to be a very efficient acousto-optic material.

Acoustic and elastic anisotropy of acousto-optic Pb2P2Se6 crystals.

We have determined experimentally the acoustic wave velocities for Pb2P2Se6 crystals and obtained complete matrices of the elastic stiffness and elastic compliance coefficients on this basis. The anisotropy of the acoustic wave velocities has been analyzed, and the spatial directions of propagation and polarization of the slowest acoustic waves have been determined. In the case of acousto-optic (AO) interaction with these waves, the AO figure of merit can reach extremely high values, thus making Pb2P2Se6 a promising AO material for the infrared spectral range.

Synthesis and spectroscopic study of several novel annulated azulene and azafluoranthene based derivatives.

A series of cyclized five-membered annulated azafluoranthene (AAF) and seven-membered annulated azulene (AA) derivatives have been synthesized and characterized by spectroscopic methods. The optical absorption and fluorescence spectra have been recorded in organic solvents of different polarity and analyzed within the semiempirical quantum chemical model PM3. In combination with the molecular dynamics simulations it properly reproduces the overall shape of the measured absorption spectra of both AA and AAF dyes including the strongest band in the region of 250-300 nm and the broad first absorption band above 400 nm. While the solvent polarity rises all the dyes exhibit the hypsochromic shift of the first absorption band and the bathochromic shift of the fluorescence band. Such opposite solvatochromic trends appear to be consistent with the Lippert-Mataga solvatochromic model. Compared to AA compounds, both AAF dyes reveal much stronger solvatochromic shift and broadening of the fluorescence band likewise the relative decrease in quantum yield on rising solvent polarity what may be an evidence for the intramolecular charge transfer mechanism being involved into the fluorescence emission. Depending on solvent polarity AA and AAF dyes emit light in the green-yellow range of the visible spectra what may be of interest for potential luminescent or electroluminescent applications.

Synthesis and optical characterization of LiKB4O7, Li2B6O10, and LiCsB6O10 glasses.

In the current work we report on the synthesis of LiKB(4)O(7), Li(2)B(6)O(10), and LiCsB(6)O(10) borate glasses. The results for their piezo-optic, acousto-optic, acoustic, elastic, refractive, optical transmission, and optical resistance properties are also presented. It is shown that some of these glasses represent efficient acousto-optic materials that are transparent down to the vacuum ultraviolet range and highly resistant to laser radiation.

Acoustic and elastic properties of Sn(2)P(2)S(6) crystals.

We present the results concerned with acoustic and elastic properties of Sn(2)P(2)S(6) crystals. The complete matrices of elastic stiffness and compliance coefficients are determined in both the crystallographic coordinate system and the system associated with eigenvectors of the elastic stiffness tensor. The acoustic slowness surfaces are constructed and the propagation and polarization directions of the slowest acoustic waves promising for acousto-optic interactions are determined on this basis. The acoustic obliquity angle and the deviation of polarization of the acoustic waves from purely transverse or longitudinal states are quantitatively analysed.

Highly efficient acousto-optic diffraction in Sn2P2S6 crystals.

We have studied the acousto-optic (AO) diffraction in Sn2P2S6 crystals and found that they manifest high values of an AO figure of merit. The above crystals may therefore be used as highly efficient materials in different AO applications.