Chang-Won Shin

Holographic polarization-selective module based on a small Dove prism coupler for magneto-optical pickup heads

A new structure for polarization-selective elements, consisting of two holographic gratings and a Dove prism coupler, is proposed. The absence of a multistage waveguide and the benefits of compact size and lightweight volume are the outstanding features of the new structure. Based on the coupled-wave theory, the analysis and design of the structure are discussed in detail to calculate the required index modulation. Several parameters, such as the recording intensity, the exposure time, and the recording angles for the fabrication of the proposed element, are determined. Under these conditions, the element is fabricated in Dupont photopolymer HRF-150-38 material and with an operating wavelength of 532 nm. A simplified pickup head is constructed to evaluate the performance of the fabricated element.

Enhanced depth-of-field of an integral imaging microscope using a bifocal holographic optical element-micro lens array

We propose and implement an integral imaging microscope with extended depth-of-field (DoF) using a bifocal holographic micro lens array (MLA). The properties of the two MLAs are switched via peristrophic multiplexing, where different properties of the MLA are recorded onto the single holographic optical element (HOE). The recorded MLA properties are perpendicular to each other: after the first mode is recorded, the HOE is rotated by 90° clockwise, and the second mode is recorded. The experimental results confirm that the DoF of the integral imaging microscopy system is extended successfully by using the bifocal MLA.

Acceleration Method for Computer Generated Hologram Using Random-sampled Wavefront Recording Plane

Random-sampled wavefront recording plane for fast computer generated hologram is proposed. This approach can accelerate computing process by replacing nonuniform sampled angular spectrum method to ray-tracing method in wavefront recording plane.

Optical characteristics of an organic-inorganic hybrid photopolymer film for holographic storage and optical application

Monomer diffusion in an organic-inorganic nanocomposite films during the holographic recording was investigated. The photopolymer films with low shrinkage were prepared by dispersing an aromatic methacrylic monomer and a photo-initiator in organic-inorganic hybrid sol-gel matrices. The shrinkage of the photopolymer film and the diffusion of monomers during the holographic recording could be controlled by optimizing the content of an organically modified silica precursor (ORMOSIL) in the sol-gel matrices. The photopolymer film showed high diffraction efficiency (>90%) under an optimized condition. Photo-sensitivity, angular selectivity and application potential for holographic data storage and optical application will be discussed.

Holographic stereogram printer for computer-generated holograms

A design and implementation of full-parallax holographic stereogram printer is presented. The holographic stereogram is synthesized using 2D perspective images of the 3D object that are rendered from multiple directions. The perspective images of the 3D scene are firstly captured by a virtual camera and transformed to two-dimensional holographic elements called hogels. The hogels are exposed using the perspective images to form the whole holographic stereogram. After all the hogels are exposed successively, a holographic stereogram can be achieved. Numerical simulation and optical reconstructions are implemented.

Complex object wave extraction using time-multiplexing in off-axis digital holography

In this paper, we present an algorithm for complex object wave extraction in off-axis digital holography using a time-multiplexing and frequency spectrum-shifting technique. The proposed approach utilizes the digital time-multiplexing technique, in which two 90-deg-rotated off-axis holograms are recorded in sequence, and corresponding spectra are subtracted in the computed Fourier domain to eliminate the DC term. Then, the two subtracted holograms are digitally multiplexed into one complex hologram in the same plane, and by shifting the spatial frequency spectra of the subtracted hologram in the spatial frequency domain, one of the two cross-correlations can be obtained in the center. This technique simply extracts the spectrum of the real image in the frequency domain than the spatial filtering method.

Development of holographic solar concentrator using holographic optical elements

In this paper, we present the development of holographic solar concentrator using holographic optical elements (HOE). The transmission HOE was evaluated by measuring the optical efficiencies of holographic gratings recorded at 532 nm wavelengths. We experimentally confirmed that holographic solar concentrator can condense the wide angle light to a single point through HOE.

Mask pattern recording of reflection type photopolymer using total internal reflection

In this paper, recording and reconstruction of micro-pattern using total internal reflection hologram applied in reflection type photopolymer are studied. The line and point patterns with the interval of 1 mum are recorded successfully and can be observed when the micro objective lenses with 100 time magnification are used.

Optical characteristics of photopolymer for holographic applications as a input beam coupler

In this paper, a holographic grating coupler based on the photopolymer has been designed and experimentally demonstrated with photopolymer of HRF 150 series at wavelength of 405 nm and we researched optical properties of OmniDex 700 series for holographic application at 532 nm. To achieve the high diffraction efficiencies in the structure, we investigated the optical properties of the material to the exposure energy and incident angles at the 532 nm wavelength, we researched the optical characteristics of the Dupont photopolymer OmniDex 700(series) and HRF 150(series) for holographic application as a input beam coupler. The performance and the optical characteristics of the volume holographic grating will be discussed in detail.

Optical properties of a photopolymer film for digital holographic storage

Tir- and mono functional monomers were dispersed in a solution of polysulfone in organic solvent containing a photo initiator and other additives. New photopolymer film was prepared by dispersing acrylic monomer in a polysulfone matrix. The Polysulfone was adopted as a binder since it affords transparent thick films with low dimensional changes during holographic recording. Optical property of the photopolymer showed high diffraction efficiency (>90%) under an optimized optical condition at 532nm laser. The angular selectivity for angular multiplexing page oriented holographic memories (POHMs), the maximum diffraction efficiency of the material during holographic recording, the diffraction efficiency of the films as a function of an incident angle of two beams, exposure energy for saturation of the holographic material and application for holographic data storage will be discussed.