• Proceedings of the KIEE Conference
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• 1987.07a
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• pp.47-50
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• 1987

There are various holographic recording materials, such as Dichromated Gelatin, Silver Halide, Thermoplastic, Photoresist. In this paper especially, we used Photoresist to make the phase holographic grating. Deep-groove diffractive grating formed in relatively thin holographic recording material is to express high diffraction efficiency. Phase holographic grating recorded In photoresist can be used very practical because it has the high diffraction efficiency, and it is possible to make a replication easily. So, it has the merit in recording the optical holographic grating than any other materials.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.614-615
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• 2009

For the high reflectance under the ambient light condition, a highly efficient diffractive reflector has been proposed, based on a micro grating structure.[1] This reflector was designed to show highly concentrated distribution of the reflected light to the normal direction of the reflector under specific incident conditions of the light. In order to apply a diffractive reflector to a reflective liquid crystal display, the coupling between the viewing angle characteristics of a liquid crystal (LC) cell and the reflective distribution of the reflector should be considered. Under the optimum configuration confirmed through the analysis of the coupling between a LC cell and a reflector, a reflective vertical alignment (VA) cell with a diffractive reflector shows contrast ratio and brightness much higher than that with a conventional bumpy reflector.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.644-647
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• 2001

Amorphous As-Ge-Se-S thin films have been studied with the aim of identifying optimum etching condition which can be used to produce holographic grating structure for use as diffractive optical elements. In this study, holographic gratings have been formed using He-Ne laser(632.8nm), and fabricated by the method of wet etching using NaOH etchant with various concentration(0.26N, 0.33N, 0.40N). The diffraction efficiency was obtained by +1st order intensity of the diffracted beam. The formed grating profiles were observed by atomic force microscope and showed that the expected grating profile could be achieved by controlling the etching time. Over-etching resulted in under-cutting of the grating lines. The highest 1st order diffraction efficiency for these gratings was about 5.05%.

• Current Optics and Photonics
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• v.6 no.4
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• pp.375-380
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• 2022

We demonstrate two types of light field displays based on waveguide grating coupler arrays: a line beam type and a point source type. Ultra violet imprinting of an array of diffractive nanograting cells on the top surface of a 50-㎛-thin slab waveguide can deliver a line beam or a point beam to a multidirectional light field out of the waveguide slab. By controlling the grating vectors of the nanograting cells, the waveguide modes are externally coupled to specific viewing angles to create a multidirectional light field display. Nanograting cells with periods of 300 nm-518 nm and slanted angles of -8.5°~+8.5° are fabricated by two-beam interference lithography on a 40 mm × 40 mm slab waveguide for seven different viewpoints. It is expected that it will be possible to realize a very thin and flexible panel that shows multidirectional light field images through the waveguide-type diffraction display.

• Journal of the Optical Society of Korea
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• v.10 no.3
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• pp.105-111
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• 2006

A novel image quality evaluation method, which is based on combination of the rigorous grating diffraction theory and the ray-optic method, is proposed. It is applied for design optimization and, tolerance analysis of optical imaging systems implementing diffractive optical elements (DOE). The evaluation method can predict the quality and resolution of the image on the image sensor plane through the optical imaging system. Especially, we can simulate the effect of diffraction efficiencies of DOE in the camera lenses module, which is very effective for predicting different color sense and MTF performance. Using this method, we can effectively determine the fabrication tolerances of diffractive and refractive optical elements such as the variations' in profile thickness, and the shoulder of the DOE, as well as conventional parameters such as decenter and tilt in optical-surface alignments. A DOE-based 2M-resolution camera lens module designed by the optimization process based on the proposed image quality evaluation method shows ${\sim}15%$ MTF improvement compared with a design without such an optimization.

• Korean Journal of Optics and Photonics
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• v.10 no.4
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• pp.348-353
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• 1999

Ray-optics approach based on the rigorous coupled wave theory, called by the rigorous ray-optics method (RROM), is developed for the calculation of couling coefficients of waveguide grating devices. The coupling coefficients of several grating structures, such as rectangular, sinusoidal, triangle, and trapezoidal shapes, are determined by the RROM, and they are compared with those obtained by conventional methods of the ray-optics method (ROM) and the coupled mode method (CMM). In the case of rectangular gratings, the coupling coefficients is evaluated in detail by various depths and duty-cycles of the grating. We have found that the RROM gives more exact solutions for the coupling coefficients of even arbitrary shapes of diffractive waveguide grating devices than the other conventional methods.

• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.392-398
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• 2003

We present a novel concept of a phase-shifting diffraction-grating interferometer, which is intended for the optical testing of concave mirrors with high precision. The interferometer is configured with a single reflective diffraction grating, which performs multiple functions of beam splitting, beam recombination, and phase shifting. The reference and test wave fronts are generated by means of reflective diffraction at the focal plane of a microscope objective with large numerical aperture, which allows testing fast mirrors with low f-numbers. The fiber-optic confocal design is adopted for the microscope objective to focus a converging beam on the diffractive grating, which greatly reduces the alignment error between the focusing optics and the diffraction grating. Translating the grating provides phase shifting, which allows measurement of the figure errors of the test mirror to nanometer accuracy.

• ETRI Journal
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• v.17 no.2
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• pp.1-10
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• 1995

We propose a novel planar optical interconnection scheme for 100 Gb/s optical packet address detection, which consists of waveguide grating couplers and a diffractive microlens integrated on a glass substrate 3-dimensionally. Length and duty cycle of the grating couplers have been determined on the bases of the ray-optic propagation-mode analysis in a slab waveguide and of the rigorous coupled-wave diffraction analysis for out-coupled radiation-modes. The 3-dimensionally integrated planar optics makes it possible to connect each address bit-signals of $TE_ 0-waveguide$ mode to the detector with a power uniformity of 6.4 % and a total coupling efficiency of 72.3 %.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.8
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• pp.906-912
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• 2012

This paper presents the new method for a six-degree-of-freedom (DOF) motion measurement and those dynamic characterizations in an ultraprecision linear stage using angle sensor-implemented grating interferometry. It consists of a diffractive optical element, a corner cube, four separate two-dimensional position sensitive detectors, four photodiodes and auxiliary optics components. From the previous study, it was confirmed that the proposed optical system could measure a six-DOF motion error in a linear stage. In this article, six-DOF motion dynamic characteristics of the stage were investigated through the step response and with respect to the conditions with a different speed of a slide table. As a result, the natural frequency and damping ratio according to a six-DOF direction was obtained. Also, it was seen that the speed of slide table had an significant effect on a six-DOF displacement motion, especially, X, which was considered as the effect of friction mechanism and local elastic mechanical deformation in a slide guide.

• Macromolecular Research
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• v.16 no.6
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• pp.532-538
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• 2008

Epoxy-based azopolymers were synthesized by the reaction of the diglycidyl ether of bisphenol A (DGEBA) or N,N-diglycidyl aniline (DGA) with disperse orange 3 (DO3) to give poly(DGEBA-co-DO3) or poly(DGA-co-DO3), respectively. Aniline-based azopolymers prepared from poly(DGA-co-An) precursors, synthesized by the reaction of DGA with aniline, were produced by the post-azo coupling reaction with diazonium salts containing various substituents. Holographic gratings were carried out to measure the diffractive efficiencies (DE) for the interference patterns of the $Ar^+$ laser from 50 to $300\;mW/cm^2$ intensity. The shorter repeating unit with higher chromophore density induced deeper surface relief gratings (SRG). Large surface gratings were observed for the aniline-based azopolymers with -COOH substituents, as compared with those for epoxy-based azopolymers. The aniline-based azopolymers with dimerized chromophores and various substituents were also synthesized to observe the effect of chromophore substituents and dimerization on the holography. The dimerized chromophores were more sensitively photoisomerized by the $Ar^+$ laser beam, and demonstrated a larger grating than that with one azo bond.