Metallic nanoparticles are a very attractive and fascinating material due to their multifunctional properties, such as
surface plasmon resonance absorption and excitation band tuning. In particular, these properties are proved to be
valuable in photothermal therapeutic applications, where the tunable, efficient near-field enhanced ablation or
photothermal energy conversions can be used to destroy cancerous cells. A similar mechanism can be applied for three-dimensional
multilayer nanopatterning of polymer matrix doped with NPs, where the field enhancement and
photothermal energy conversion are utilised to produce micro-explosions and voids. Previously, it was reported that
engineering the morphology of nanoparticles (rod and shell shape) can greatly enhance the field enhancement and
photothermal conditions. Here, we numerically study the field enhancement efficiencies of nanparticles with
heterogeneous morphologies (such as metal - dielectric - metal core-shell structures), and compare their efficiencies to
conventional nanosphere and nanoshell structures. Unlike the previous approximate analytical models, the SPR
excitation and field enhancement efficiencies are numerically simulated, using the frequency-dependent finite-difference
time domain method under tightly focused ultrashort pulse laser irradiation to accurately emulate the experimental
conditions.
Recently, a lot of interests have been focused on surface plasmon resonance (SPR), generated by the charge density oscillation existing on the interface between dielectric and metal surface. This particular surface wave has been widely used for sub-wavelength scale photonic circuits, fluorescence microscopy, bio-sensing devices, and photonic display applications. Also, it has a lot of potentials from holographic optical devices to holographic display applications. The
measurement of SPR can be simply evaluated by the well-known Kretchmann-Raether attenuated total reflection geometry using angle multiplexing of the incident wave. Based on these concepts, we propose and analyze a plasmon-coupled waveguide and a polymethyl-methacrylate (PMMA) metal thin film grating structure for optical beam coupling and splitting applications. For efficient beam coupling and splitting, we analyze the SPR phenomenon and design plasmon-coupled waveguide structures and the grating structures. To form the PMMA-metal lamella grating structure, we inscribe the grating on the PMMA layer by using excimer laser with the wavelength of 244nm. Then, we deposit gold on the PMMA grating. Finally some experimental results, discussion, and its practical photonic applications are provided.
We analyze the optical transmission characteristics of prism sheet layers based on a geometrical approach. An analytic method for finding the radiant intensity profile of the light transmitted through a single prism sheet for an incident light with arbitrary radiant intensity profile is developed. It is shown that the output radiant intensity profile is the inner product of the newly defined partial transmission coefficient distribution of the prism sheet and the input radiant intensity profile. The developed analysis method for a single prism sheet is immediately generalized to analyze prism sheet layer being composed of several prism sheets.
KEYWORDS: 3D image reconstruction, 3D displays, Holograms, 3D image processing, Computer generated holography, Integral imaging, Spatial light modulators, Holography, Displays, 3D image enhancement
For large viewing-angle enhancement in three-dimensional (3D) display, a dynamic computer-generated holographic display system combined with integral imaging is proposed and implemented using a single phase-type spatial light modulator and an elemental lens array. For viewing-angle enhanced colorized 3D integral image display the computer-generated holograms have been synthesized and scaled for minimizing the color dispersion error in the hologram plane. Using the integral imaging and synthetic phase holography, we can get 3D images with full parallax and continuously varying viewing-angle range of +/-6 degree. Finally we show some experimental results that verify our concept.
Several issues on the optimal diffractive beam shaping with a dynamic phase spatial light modulator are addressed. As for design theories, the optimal design method of the phase holograms considering the functional relationship between phase and amplitude modulations of the phase spatial light modulator is described. To achieve the optimal trade-off between diffraction efficiency and smoothness of the obtained diffraction images, the iterative Fourier transform algorithm with adaptive regularization parameter distribution is devised. Regarding experimental issues, we propose a beam shaping system configuration with the genetic feedback tuning loop in which the simplified genetic algorithm is employed to finely compensate the internal aberration of the optics in the beam shaping system. It is shown that the real-time tuning of the phase holograms for accurate beam shaping is possible using the dynamic behavior of the spatial light modulator.
A full-color auto-stereoscopic video display system has been introduced and developed using only a single phase-only spatial light modulator, a simple projection lens module, and three laser diode sources with the wavelengths of 635nm (red), 532nm (green), and 473nm (blue). Full-color stereoscopic input video frames are separated by each red, green, and blue component with respect to each stereo eye view for a 3D image frame. Each hologram is then optimized by a modified iterative Fresnel transform algorithm method, for the reconstruction of each gray-level quantized stereo image without color dispersion. To solve the color dispersion problem we applied scaling constraints and phase-leveling techniques for each hologram. Then the optimized holograms are synthesized with direction-multiplexed holograms and modulated by a single phase-type spatial light modulator. The modulated signals are Fourier-transformed by an achromatic lens and redirected to each viewer's eye for the reconstruction of the composed full-color auto-stereoscopic 3D display. Experimentally, we demonstrated that the designed computer-generated holograms were able to generate full-color stereoscopic 3D video images without any use of glasses.
KEYWORDS: Diffractive optical elements, Diffraction, Global system for mobile communications, Convolution, Deconvolution, Gaussian beams, Detection and tracking algorithms, Mathematical modeling, Coherence (optics), Transformers
A novel design method of diffractive optical element for shaping Gaussian Schell model beams is investigated. In the design, it is important to solve a deconvolution problem for obtaining diffraction image with edge-sharpness degraded by the convolution effect of the partially coherent Gaussian Schell model beam. In this paper, a simple heuristic approach to the deconvolution problem is addressed. It is shown that an extra rim pattern around the target diffraction image can lighten the unwanted edge-blur of the diffraction image. The algorithm for generating the extra rim pattern is explained.
In this paper, the applications of holographic devices for optical communications are reviewed and discussed. In dense wavelength division multiplexing (DWDM) optical communication systems, holographic devices have some potential applications to satisfy the complex requirements of the systems. We explain recent accomplishment in this field using holographic gratings (HGs) recorded in a photorefractive crystal or a photopolymer. General properties of the HG as a filter are reviewed. We note that the photopolymer HG can be used as a wavelength demultiplexer in DWDM system. It uses spatial dispersion properties of diffraction grating, which provides wavelength-dependent diffraction angle change to separate the multiplexed wavelength channels. The HG device has inherent advantages compared to the other device technologies. As specific applications of the device, we propose chromatic dispersion management of the multiple channel wavelength demultiplexer, channel wavelength tuning of the device output, and double band demultiplexer using superposed HGs. Also, we discuss optical signal routing using computer-generated holograms (CGHs) on a phase spatial light modulator. We expect that these HG devices and CGH system can exploit phase control, tunability, multiplexing and dynamic imaging control of holograms to cope with various DWDM system requirements.
We introduce the concept of directional diffractive optical elements (DOEs) for LCD backlight illumination for 3D display systems. Stereoscopic images can be obtained by two camera systems. And then, they are displayed at an LCD by interlacing. To generate 3D images, the LCD is programmed to display left and right images of a stereo pair on alternate rows of pixels. The light is diffracted by the DOEs designed for splitting the viewing directions and for adjusting the size of the viewing zones. The lines are spaced with respect to the LCD pixel rows such that the left eye sees all the lines through the odd rows of the LCD, while the right eye sees them through even rows. The DOEs are designed by iterative Fourier transform algorithm for high diffraction efficiency and uniform illumination distribution. For eliminating the twin image noise, the DOEs are designed by eight-quantized levels and synthesized for generating the stereoscopic viewing region. We discuss the design issues of this method and also discuss the advantages of this method over the conventional lenticular method. We will also discuss the initial experiment of the DOE characteristics for this purpose.
In this paper, we propose and examine mask design methods for fabricating optical devices containing multiple holographic gratings. As the conventional fiber Bragg grating fabrication, the mask is also required to achieve compactness and accuracy in this case. However, for the case where there needs multiplexing of several holographic gratings in the same volume of the recording medium, the mask should provide multi-order diffractions and control their relative diffraction efficiencies. We propose two methodologies for the required mask, cascaded phase mask and polymeric angularly multiplexed holographic mask. The cascaded phase mask is composed of the multi-order generating mask and the Bragg mask of two-order diffraction. The polymeric angularly multiplexed holographic mask is a kind of commonly referenced multiplexed holograms. The mask design and fabrication processes are examined. Multiple holographic grating recording in the photorefractive crystal with designed mask is discussed. In order to exclude cross diffraction order modulations, there needs to control the density of acceptors in photorefractive crystal case.
Multi-phase and binary-phase computer-generated holograms were designed and demonstrated for full-color image generation. Optimize a phase profile of the hologram that achieves each color image, we employed a simulated annealing method. The design binary phase hologram had the diffraction efficiency of 33.23 percent and the reconstruction error of 0.367 X 10-2. And eight phase hologram had the diffraction efficiency of 67.92 percent and the reconstruction error of 0.273 X 10-2. The designed BPH was fabricated by micro photolithographic technique with a minimum pixel width of 5micrometers . And the it was reconstructed using by two Ar-ion lasers and a He-Ne laser. In addition, the color dispersion characteristic of the fabricate grating and scaling problem of the reconstructed image were discussed.
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