• New Physics: Sae Mulli
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• v.68 no.12
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• pp.1378-1383
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• 2018

Multi-wavelength holography has a better axial range than single-wavelength holography, thus allowing unambiguous phase imaging. Noise amplification is the limiting factor in multi-wavelength holography as noise is amplified by a factor equivalent to the magnification of the wavelengths. Here, we propose a new algorithm to remove noise amplification in multi-wavelength holography. The proposed method does not use phase unwrapping and removes $2{\pi}$ ambiguities. Experiments and numerical simulations indicated that the proposed method is fast, has low noise, and is useful for measuring samples with arbitrary step heights.

• Journal of the Optical Society of Korea
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• v.13 no.2
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• pp.173-177
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• 2009

Digital holographic microscopy allows optical path difference measurement. Optical path difference depends on the both refractive index and morphology of sample. We developed a dual-wavelength in-line digital holographic microscope that can measure simultaneously the refractive index and morphology of a sample, providing highly precise three-dimensional information. Here we propose theoretical and experimental methods for dual-wavelength in-line digital holographic microscopy. The measured data were reasonable, although there was data error. By improving the experimental method, we could measure the refractive index more precisely and obtain more accurate three-dimensional information on samples.

• Journal of the Optical Society of Korea
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• v.18 no.5
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• pp.495-499
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• 2014

In this paper, a method is proposed for simultaneously measuring the front and back surface profiles of transparent micro-optical components. The proposed method combines a dual-wavelength digital holographic microscope with liquids to record holograms at different wavelengths, and then numerically reconstructs the three-dimensional phase information to image the front and back sides of the sample. A theoretical model is proposed to determine the surface information, and imaging of an achromatic lens is demonstrated experimentally. Unlike conventional interferometry, our proposed method supports nondestructive measurement and direct observation of both front and back profiles of micro-optical elements.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.123-130
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• 2009

In this paper, we designed and fabricated an input-output coupler system using two or three volume gratings at 632.8nm wavelength. The additional third grating is added at the output coupler to enhance the overall efficiency. The experimental results show that the total system throughput reaches 63% with two-grating and 75% with three-grating input-output coupler. We also present a design method to obtain the desired output power ratio between the gratings.

• Korean Journal of Optics and Photonics
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• v.12 no.1
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• pp.17-24
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• 2001

Two-dimensional binary-phase diffraction gratings which can be employed to fabricate two- and three-dimensional periodic structures are designed and analyzed using rigorous coupled-wave analysis. These gratings serve as phase-masks which generate several diffracted waves from a normally incident beam and thus can produce a periodic interference pattern in space via nearfield holography. The properties of the diffracted beams can be controlled by varying the polarization and wavelength of the incident beam, surface-profile, groove depth and duty cycle of the mask. For the two-dimensional structure, optimum results can be obtained when the diffraction efficiency of the zero-order beam is minimized while that of the first-order maximized. On the other hand, when the diffraction efficiency of the zero-order is appreciable or even greater than other orders, we can obtain a variety of three-dimensional interference patterns which may be used to fabricate photonic crystals of tetragonal-body-centered and hexagonal structures in a submicron scale. scale.