We report the observation of a photorefractivelike nonlinearity responsible for the formation of giant relief modulations in amorphous semiconductor glasses. The photoinduced softening of the matrix, formation of defects with enhanced polarizability, and their drift under the optical field gradient force is believed to be the origin of the mass transport.

A new series of liquid crystalline diblock copolymers composed of a polystyrene and a polymethacrylate with an azobenzene moiety in the side chain were synthesized through atom transfer radical polymerization and characterized by various techniques. Photoinduced birefringence of diblock copolymers and the azobenzene homopolymer was investigated and compared under different excitation conditions. The results show that the microdomain structures characteristic of diblock copolymers hinder the photoalignment of azobenzene mesogenic groups.

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A cyclic side-chain liquid crystalline polymer (SCLCP) bearing azobenzene mesogens, namely, poly{6-[4-(4-methoxyphenylazo)phenoxy]hexyl methacrylate} (PAzoMA), was successfully synthesized by using "click" cyclization of the linear polymer precursor with alkyne and azide end groups. Samples of cyclic-PAzoMA of various molecular weights were prepared, characterized, and studied in comparison with their linear counterparts. The results show that the topological constraint arising from the tortuosity of the ring structure and the absence of chain ends in cyclic-SCLCPs affects profoundly the liquid crystalline (LC) phase transitions (temperature, enthalpy, and entropy) of mesogenic side groups and that this topological effect is more prominent for smaller SCLCP rings. Moreover, the photoinduced anisotropy in films as a result of the trans-cis photoisomerization of azobenzene mesogens was investigated, and cyclic-PAzoMA was found to behave differently from linear-PAzoMA. On the one hand, the cyclic polymer exhibits a nonmonotonic rise and erasure of birefringence upon linearly and circularly polarized excitation (488 nm), respectively, in contrast with the linear polymer displaying monotonic changes. On the other hand, unlike the linear polymer, the photoinduced orientation of azobenzene mesogens in cyclic-PAzoMA cannot be enhanced upon annealing in the nematic phase. All these manifestations of the topological constraint suggest that cyclization offers a new way to change the coupling between mesogenic side groups and chain backbone of SCLCPs, and their interplay under the additional topological effect may generate new behaviors that are of interest to be explored.

Electrically variable gradient index liquid crystal lens is developed that uses flat uniform liquid crystal layer and electrodes. The spatial modulation of the electric field across the lens aperture is obtained by the modulation of the effective dielectric constant of an integrated doublet lens structure. The dielectric constants of two materials, composing the doublet, are chosen to be different at electrical driving frequencies, while their optical refractive indexes are the same, hiding thus the structure from the optical point of view. This "hidden layer" approach decouples the electrical and optical functions of that structure, increases significantly the performance of the lens and enables new functionalities. The technical performance and various driving schemes of the obtained lens are presented and analyzed.

The photoexcitation, relaxation, and optical erasure regimes of spiropyran- (SP-) doped polymer films were studied. Cellulose acetate, poly(vinyl acetate), and poly(methyl methacrylate) (PMMA) were used as host polymer matrices. We studied the character of the photoreaction for both coloring and bleaching processes. Reversible holographic recording in SP-PMMA films and the origin of the photochemical fatigue was studied upon repeated UV-visible irradiation cycles.

We investigate the electro-optical properties of polymer stabilized nematic liquid crystals produced by in situ photopolymerization technique using Gaussian laser beam. The distribution of refractive index in such structure under the action of a homogeneous electric field reveals a non-homogeneous lens-like character, approximately reproducing the intensity transverse distribution in the photopolymerizing beam.