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Photorefractive properties of tin-doped CdTe crystals are studied. The material demonstrates sensitivity for low-intensity recording. A one-center model of the space-charge formation perfectly describes the experimental results. The tin impurity center is characterized using the data of optical absorption and light-induced absorption spectroscopy, pseudo-3D mapping of the photoabsorption, magnetic circular dichroism, and optical detection of magnetic resonance. Spectroscopic studies confirm appropriateness of the one-center model for describing the space-charge formation with tin as a main photorefractive center. Optical ionization (neutralization) energies are estimated for phototransitions from Sn+ (1.14 eV) and Sn0 (1.09 eV). Possible ways for improvement of the photorefractive performances are discussed.

A chiral nematic (N*) liquid crystal (LC) was hybridized with a z-cut iron doped lithium niobate (Fe:LN) substrate and exposed with a focused continuous wave diode laser beam. The N* LC layer was confined with a cover glass to provide a homogeneous LC layer thickness. Two distinct kinds of test cells were investigated, one with an uncoated glass covering slip and one with an indium tin oxide (ITO) coated cover glass. Photo generated electric fields (generated in the Fe:LN) resulted in a localized defect formation and textural transitions in the N* LC. Due to field confinement, the field induced responses were more localized in samples with ITO coated cover glasses. By scanning the laser beam on programmed trajectories, formation of persistent patterns could be achieved in the N* LC layer. Polarized optical microscopy of the exposed samples revealed that these patterns consisted of adjacent circular Frank-Pryce defects. Exposure with a slightly defocused laser beam could be applied selectively to erase these patterns. Thus, a promising method is reported to generate reconfigurable patterns, photonic motives, and touch sensitive devices in a hybridized N* LC with micron accuracy.

The photorefractive effect in Sn2P2S6 (SPS) is caused by a spatial redistribution of both positively charged and negatively charged carriers, which leads to the formation of two out-of-phase space charge gratings that partially compensate each other in the steady state. The unusual intensity dependence of the compensation grating buildup time is reported in this article for antimony doped SPS; it is explained by the thermal excitation of electrons into conduction band from the optically recharged Sb3+ → Sb2+ impurity ions.

We studied a system of a core-shell nanowire array in the liquid crystal (LC) matrix 5CB supposing that the nanowire shell permittivity is anisotropic with radially power-law dependent components. The nanowire core material is either silver or gold. We calculated the effective permittivity tensor of the core-shell nanowire array in the LC matrix, and show that the system under consideration can possess two hyperbolic metamaterial (HMM) areas: where the real part of the effective permittivity component parallel to the nanowire is negative, and the real part of the effective permittivity component perpendicular to the nanowire is negative. Dependence of the frequency position for these areas on the core-shell nanowire parameters and the LC matrix orientational state is studied.

Doping photorefractive single crystals of Sn2P2S6 with antimony introduces both electron and hole traps. In as-grown crystals, Sb3+ (5s2) ions replace Sn2+ ions. These Sb3+ ions are either isolated (with no nearby perturbing defects) or they have a charge-compensating Sn2+ vacancy at a nearest-neighbor Sn site. When illuminated with 633 nm laser light, isolated Sb3+ ions trap electrons and become Sb2+ (5s25p1) ions. In contrast, Sb3+ ions with an adjacent Sn vacancy trap holes during illumination. The hole is primarily localized on the (P2S6)4− anionic unit next to the Sb3+ ion and Sn2+ vacancy. These trapped electrons and holes are thermally stable below ∼200 K, and they are observed with electron paramagnetic resonance (EPR) at temperatures below 150 K. Resolved hyperfine interactions with 31P, 121Sb, and 123Sb nuclei are used to establish the defect models.

A liquid crystal light valve is an optically controlled spatial light modulator made as a cell with liquid crystal on a photoconductive substrate. Dynamic holograms recorded in such a hybrid device may give rise to the amplification of one of the recording beams at the expense of the other. In the present work, liquid crystal light valves with different thicknesses of the liquid crystal layer are studied at various conditions of the dynamic grating recording aiming to maximize the signal beam amplification in the infrared. A seventeen-fold gain is achieved in the improved cell for optimal recording conditions.

We model electromagnetic cloaking of a spherical or cylindrical nanoparticle enclosed by an optically anisotropic and optically inhomogeneous symmetric shell, by examining its electric response in a quasi-static uniform electric field. When the components of the shell permittivity are radially anisotropic and power-law dependent (ε~r(m)) whereris distance to the shell center, and m a positive or negative exponent which can be varied), the problem is analytically tractable. Formulas are calculated for the degree of cloaking in the general case, allowing the determination of a dielectric condition for the shells to be used as an invisibility cloak. Ideal cloaking is known to require that homogeneous shells exhibit an infinite ratio of tangential and radial components of the shell permittivity, but for radially inhomogeneous shells ideal cloaking can occur even for finite values of this ratio.

The purpose of this paper is to find the polarizations and spatial orientations of the two interacting counterpropagating coherent light waves which ensure the largest beam coupling in monoclinic photorefractive crystal. The results of calculations are presented that are verified experimentally with Sn₂P₂S₆.

This novel joint feature issue on “Hybrid organic–inorganic materials for photonic applications” in Applied Optics and Optics Materials Express comprises 14 papers on liquid crystals, polymers, photoconductive materials, and gratings and filters. It is hoped that this feature issue encourages and stimulates further research to into hybrid materials with enhanced linear and nonlinear optical properties, their mechanisms of operation, and their applications.

We present a method for the preparation of transparent Tb doped zirconia (Tb:ZrO2) ceramics that luminesce in the visible. The visible luminescence is temperature dependent, yielding samples that have integrated temperatures sensing capabilities. Our approach is to simultaneously react and densify ZrO2 and Tb4O7 using current activated pressure assisted densification (CAPAD). The Tb dopant serves to both stabilize the tetragonal phase of zirconia and for emitting light. The Tb:ZrO2 ceramics have an excellent combination of structural and optical properties; the toughness is comparable to yttria stabilized zirconia and the transparency in the visible is high. Moreover, the luminescent lifetimes are long and amenable to luminescent thermometry. The ceramics have promise as thermal barrier materials and high-strength windows with “built-in” temperature measurement capabilities.

The spatial distribution of new beams generated above the threshold of absolute instability of two counterpropagating incoherent light waves is studied and compared with the results of calculation.

The q-parameter of a Gaussian beam is a convenient way to determine its paraxial propagation in a medium as well as in an optical system under external or induced lensing. The assumption is that the Gaussian beam either is scalar or has a linear polarization. It is shown that propagation of radially polarized Gaussian beams in a medium and/or under lensing can be readily analyzed rather simply by knowing the q-transformation of the underlying scalar Gaussian beam. The exact profiles of the longitudinal and transverse components of initially radially polarized lowest-order Laguerre-Gaussian beams are derived and compared with those of the linearly polarized Gaussian beam. It can be readily shown that the longitudinal component of the polarization does not contribute to real power flow at the focal plane. The focal shift and the Guoy phase during lensing are calculated, again based on the underlying q-parameter. The methodology for extension to higher-order Laguerre-Gaussians is also developed. Finally, waveguiding of radially polarized beams in a graded index square law medium is analyzed, and conditions for the existence of radially or longitudinally polarized modes are derived.

Considerable improvement of a transient two-beam coupling gain is reported for Sn(2)P(2)S(6), a photorefractive crystal that possesses two types of movable charge carrier. A gain enhancement occurs if the phase difference of the interacting beams is abruptly changed to pi. Enhancement is also achieved with periodic phase variations of zero and pi between two discrete states at modulation frequencies lower than the smallest of two reciprocal characteristic times of the space-charge formation.

We report on the determination of liquid crystal pre-tilt inside cells fabricated using single crystal birefringent and dichroic windows of cerium doped strontium barium niobate. We show that the average pre-tilt is significantly affected by the crystalline windows, leading to much larger values than those obtained with glass windows using identical fabrication methods. The same technique can be used to determine pre-tilts as large as 40 degrees, which is significantly larger than normally measurable using the cell rotation method.

The spatial distribution of the power transfer achieved by contradirectional two-beam coupling using self-pumped photorefractive reflection gratings is investigated in two materials with different photorefractive gain coefficients, LiNbO3:Fe and KNbO3:Fe. Incremental portions of the volume grating are erased optically by inducing thin optical damage planes, reducing the overall two-beam coupling efficiency. By monitoring the effect of local grating disruption, the distribution of power transfer is spatially resolved throughout the crystal, and the results are found to be in agreement with our theoretical predictions.

We theoretically demonstrate beam shaping through adaptive feedback in an acousto-optic device with electrical feedback by using experimentally determined parameters. Cases of positive feedback and negative feedback from undiffracted and diffracted orders are investigated. In addition, we demonstrate the dependence of the final value of the induced grating strength in the acousto-optic cell on the feedback parameters.