Simplified spectropolarimetry using reactive mesogen polarization gratings

\u3cp\u3eThe measurement of complete polarimetric parameters for a broad spectrum of wavelengths is challenging because of the multi-dimensional nature of the data arid the need to chromatically separate the light under test. As a result, current methods for spectropolarimetry and imaging polarimetry are limited because they tend to be complex and/or relatively slow. Here we experimentally demonstrate an approach to measure all four Stokes parameters using three polarization gratings arid four simultaneous intensity measurements, with potential to dramatically impact the varied fields of air/space-borne remote sensing, target detection, biomedical imaging/diagnosis, and telecommunications. We have developed reactive mesogen polarization gratings using simple spin-casting and holography techniques, and used them to implement a potentially revolutionary detector capable of simultaneous measurement of full polarization information at many wavelengths with no moving or tunable elements. This polarimeter design not only enables measurements over a likely bandwidth of up to 70% of the center wavelength, it is also capable of measurements at relatively high speed (MHz or more) limited only by the choice of photo-detectors and processing power of the system. The polarization gratings themselves manifest nearly ideal behavior, including diffraction efficiencies of greater than 99%, strong polarization sensitivity of the first diffraction orders, very low incoherent scattering, and suitability for visible and infrared light. Due to its simple and compact design, simultaneous measurement process, and potential for preserving image registration, this spectropolarimeter should prove an attractive alternative to current polarization detection arid imaging systems.\u3c/p\u3

Luminescent object comprising aligned polymers having a specific pretilt angle

A first aspect of the invention relates to a luminescent object comprising an aligned polymer that contains an oriented photoluminescent material, said aligned polymer having a pretilt angle of 10-90 DEG . The luminescent object according to the present invention may advantageously be employed in luminescent solar concentrator systems as it enables highly efficient transportation of radiation emitted by the photoluminescent material following exposure to incident solar light. Another aspect of the invention concerns a photovoltaic device comprising an electromagnetic radiation collection medium containing the aforementioned luminescent object and a photovoltaic cell capable of converting optical radiation to electrical energy which is optically coupled to the luminescent object.; Further aspects of the invention include a fluorescent light activated display and a room lighting system comprising the aforementioned luminescent object

An efficient illumination system for liquid crystal displays incorporating an anisotropic hologram

\u3cp\u3eAn anisotropic hologram is combined with an edge-lit planar waveguide to produce an improved liquid crystal display (LCD) backlight. A holographic-polymer dispersed liquid crystal material is exposed to a slanted one-dimensional interference pattern to produce an anisotropic Bragg transmission grating with strong diffraction for P-polarized light and very low diffraction for S-polarized light. While the hologram is recorded at a UV wavelength (351 nm), light at visible wavelengths propagating from the waveguide edge is redirected toward the normal direction. The emission is collimated, polarized, and unidirectional, effectively integrating several functions that are typically embodied in separate optical films in a conventional LCD.\u3c/p\u3

Polymerization-induced diffusion as a tool to generate periodic relief : a combinatorial study

Polymeric relief structures are extensively used in display technology due to their ability to redirect light in a controlled way. Photo-embossing is a new photo-lithographic technique to generate surface relief structures using photopolymers. In the present paper we show a combinatorial methodology to explore this technique. We have prepared and evaluated (using automated atomic force microscopy) 2-dimensional libraries of photo-embossed gratings, each library with a gradient in period and a gradient in either exposure energy or development temperature or film thickness or photoinitiator concentration or monomer to binder ratio. We show how this combinatorial approach helps us to better understand the photo-embossing process. In addition, we show that this methodology is an effective tool to identify processing conditions resulting in optimum shape and height of the polymeric relief micro-structures to be used in specific applications