Advanced imaging and display techniques are widely explored for realistic content capture and visualization but cannot fully follow the miniaturization and mobility trends in technology. Wide field-of-view displays require large surfaces and image capture requires separate installation of cameras having separate footprints and perspective views. Here we propose a novel, portable dual purpose passive screen that can simultaneously facilitate display and imaging with unprecedented features and performance. The optical design of the screen is presented. A prototype of the dual-purpose screen paired with a camera and a low power mobile projector is demonstrated. The developed screen has size of 28×21cm2 to facilitate capture of eye contacted perspective view and displays high-quality images with high-brightness (>100cd/m2 ) using only 15 lumen pico projector.
We have investigated photorefractive (PR) properties of a polymer composite with low glass-transition temperature (Tg) in a symmetric reflection geometry. A diffraction efficiency of more than 30% is observed in 105μm thick devices. In low Tg photorefractive polymers, poling of the nonlinear optical chromophores at room temperature leads to birefringence in the material. The birefringence will alter the Bragg condition, as the propagation vectors for object and reference beams as well as the readout angle are influenced. We observed the Bragg-mismatch effect that caused a reduction in diffraction efficiency as the external field is increased. We have varied the angle of readout beam slightly at each bias field to get the highest efficiency.
We report the photorefractive properties of tetraphenyldiaminobiphenyl (TPD) based polymer composites
that have been developed for single pulse laser operation at 532 nm. With an optimized composite, we
demonstrate more than 50% diffraction efficiency using 4 mJ/cm2 single shot writing and 633 nm
continuous wave (cw) beam reading. The present devices showed a 300 μs fast response time. This
reveals the potential for these polymer devices in applications which require fast writing and erasure. Since
the writing pulse-width is in nanosecond time scale, the recording is totally insensitive to vibrations. These
devices can also be used as a stepping stone to realize all-color holography since they are sensitive to both
green (532nm) and red (633nm) wavelengths. The holograms can be written with either of these two
wavelengths and can be read by the same wavelength or the other wavelength with high diffraction
efficiency. This demonstrates that these devices have the advantage of performing two-color holography, a
step closer to a dynamic full-color holographic recording medium.
We propose and demonstrate a novel technique for efficient local fixing of photorefractive polymer hologram using a
laser beam. In the new technique, a CO2 laser beam is used to heat the sample and a local hologram can be fixed easily.
By using glass and sapphire with particular thickness as the substrates for the photorefractive device, the hologram can
be fixed efficiently and at much faster speed. The fixation efficiency can be greater than 80% and the hologram can be
fixed in a few seconds. This technique is critical for dynamic holographic 3D display and holographic data storage.
We describe the material characteristics and photorefractive properties of novel tetraphenyldiaminobiphenyl (TPD) based polymer composites that were developed for operation wavelengths up to 1 micron. With an optimized composite, we demonstrated more than 50% external diffraction efficiency coupled with a fast response time of about 35 ms at 980 nm. In addition to this high performing composite, we have developed a composite with high two beam coupling gain (300 cm-1). To accomplish these attractive photorefractive properties in the near-infrared, we explored the chemical flexibility of the guest-host approach. We employed a new dye with enhanced near-infrared absorption to extend the sensitivity into this long wavelength range. Styrene-based chromophores were utilized to enable high refractive index modulation. We explored ellipsometry as well as photo-conductivity measurements to optimize the composition of the composites. In addition to the composites that contain a single chromophore species, we also analyzed samples prepared with a mixture of chromophores. Our studies reveal the potential of this new polymer-composite family to extend the operation wavelength of the photorefractive materials to even longer wavelengths. Attractive photorefractive properties coupled with long wavelength sensitivity make these materials potential candidates for imaging and communication applications.
We report on the photorefractive properties of two polymer composites that utilize a new bis-triarylamine side-chain polymer matrix. Correctly locating the frontier orbitals of the new transport manifold with respect to the HOMO levels of chromophores, allows stable continuous operation over exposure levels of more that 4 kJ/cm2 when samples are electrically biased at 57 V/μm. This operational stability is combined with video-rate compatible grating build-up times and a dynamic range that allows index modulations of 3 x 10-3 and gain coefficients on the order of 100 cm-1 at moderate fields. The thermal stability of one of the composites reported is excellent, showing no signs of phase separation even after one week at 60°C. A comparison with the stability of composites where the new matrix was replaced by PVK is also presented.