Optical beam steering and switching by optically controlled liquid crystal spatial light modulator with angular magnification by high efficiency PTR Bragg gratings.

Non-mechanical optical beam steering and switching is produced by optically controlled liquid crystal spatial light modulator with angular magnification by high efficiency volume Bragg gratings recorded in a photosensitive PTR glass. Small angle beam deflection in a photoactive liquid crystal cell is produced by exposing it to a controlling beam from an external source of radiation with predetermined distribution of power density which causes predetermined spatial gradients of a refractive index in a liquid crystal cell and, therefore, refraction of a controlled beam which is made to propagate in the region with spatial gradient of the refractive index. Large angle beam deflection is produced by a volume Bragg grating with angular selectivity adjusted in such way that small angle scanning produced by optically controlled liquid crystal spatial light modulator results in change of diffraction efficiency from zero to 100% for switching the beam for two Bragg angles

Nonlinear Lens Mapping Of Optical Substrates

We have tested a technique for characterizing optical substrates using high sensitivity of the constant of nonlinear refraction to the structural and compositional homogeneity of the material. The technique consists in two steps: first the substrate is positioned in the focal region of a lens where the signal of the nonlinear phase shift is maximal and, second, the substrate is scanned in directions transverse to the propagation direction of the probe laser beam. The measured variations are proportional to variations in the nonlinear phase shift across the substrate and reflect distribution of parameters that contribute into the nonlinear phase shift, including the absorption coefficient and substrate thickness. This technique can be used for mapping trace amounts of impurities, dopants and inclusions as well as varying external/boundary conditions in glass substrates, liquid crystals, and other materials. As an example, we have visualized subtle changes inflicted on a holographic glass by UV exposure

Broadband Waveplate Lenses

We report on lenses that operate over the visible wavelength band from 450 nm to beyond 700 nm, and other lenses that operate over a wide region in the near-infrared from 650 nm to beyond 1000 nm. Lenses were recorded in liquid crystal polymer layers only a few micrometers thick, using laser-based photoalignment and UV photopolymerization. Waveplate lenses allowed focusing and defocusing laser beams depending on the sign of the circularity of laser beam polarization. Diffraction efficiency of recorded waveplate lenses was up to 90% and contrast ratio was up to 500:1

Transparent thin film polarizing and optical control systems

We show that a diffractive waveplate can be combined with a phase retardation film for fully converting light of arbitrary polarization state into a polarized light. Incorporating a photonic bandgap layer into a system of such polarizers that unify different polarization states in the input light into a single polarization state at its output, rather than absorbing or reflecting half of it, we developed and demonstrated a polarization-independent optical controller capable of switching between transmittive and reflective states. The transition between those states is smoothly controlled with low-voltage and low-power sources. Using versatile fabrication methods, this “universally polarizing optical controller” can be integrated into a thin package compatible with a variety of display, spatial light modulation, optical communication, imaging and other photonics systems

Visualization 1: Digital polarization holography advancing geometrical phase optics

Polarized image of an “invisible” cat revealed by inserting and removing a polarizer. Originally published in Optics Express on 08 August 2016 (oe-24-16-18297

Visualization 3: Digital polarization holography advancing geometrical phase optics

Sample with the invisible photo of George Washington (the background is The New York Times homepage) Originally published in Optics Express on 08 August 2016 (oe-24-16-18297