• Korean Journal of Optics and Photonics
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• v.28 no.2
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• pp.53-58
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• 2017

This paper presents the design and fabrication of a planar nano-diffraction grating for an integrated miniature spectrometer module. The proposed planar nano-diffraction grating consists of nonuniform periods, to focus the reflected beams from the grating's surface, and an asymmetrical V-shaped groove profile, to provide uniform diffraction efficiency in the wavelength range from 400 to 650 nm. Also, to fabricate the nano-diffraction grating using low-cost UV-NIL technology, we analyzed the FT-IR spectrum of a uvcurable resin and optimized the conditions for the UV curing process. Then, we precisely fabricated the polymeric nano-diffraction grating within 5 nm in dimensional accuracy. The integrated spectrometer module using the fabricated polymeric planar nano-diffraction grating provides spectral resolution of 5 nm and spectral bandwidth of 250 nm. Our integrated spectrometer module using a polymeric planar nano-diffraction grating serves as a quick and easy solution for many spectrometric applications.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.3
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• pp.73-77
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• 2015

This paper presents integrated polymeric spectrometer module which offers compact size, easily-fabricated structure and low cost. The proposed spectrometer module includes the nano diffraction grating with non-uniform pitch and planar optical waveguide with concave mirror to be fabricated by UV imprint lithography. To increase the reflection efficiency, we designed the nano diffraction grating with triangular profiles. The polymeric planar spectrometer includes a spectral bandwidth of 700 nm, resolution of 10 nm and precision below 5 nm. This polymeric planar spectrometer is well-suited for sensor system.

• Journal of the Optical Society of Korea
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• v.15 no.3
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• pp.216-221
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• 2011

A diffraction grating is a highly symmetric optical element with a physical structure that is invariant under translational spatial movements. The translational symmetry is reflected in the fields that are diffracted from the grating. Here, we introduce a plane-parallel mirror pair onto the grating, which translates the fields through double reflections, and we describe a method of exploiting the symmetry to enhance the spectral resolution of a diffraction grating beyond the limit that is set by the number of grooves. The mirror pair creates another virtual grating beside the original one, effectively doubling the number of grooves. Addition of more mirror pairs can further increase the effective number of grooves despite the increased complexity and difficulty of experimental implementation. We experimentally demonstrate the spectral linewidth reduction by a factor of four in a neon fluorescence spectrum. Even though the geometrical restriction on the mirror deployment limits our method to a certain range of the whole spectrum, as a practical application example, a bulky spectrometer that is nearly empty inside can be made compact without sacrificing the resolution.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.189-196
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• 2002

The components and alignment parameters of a flat-field soft x-ray spectrometer used in the wavelength range below 50 $\AA$ are determined, and the characteristics of the spectrometer are analyzed. It consists of a toroidal mirror, a slit, a varied line-spacing concave grating, and a soft x-ray detector. The space-resolved spectral image of a source is formed on a single plane using the tordidal mirror and the 2400-grooves/mm varied line-spacing concave grating. The former is used to compensate for the astigmatism caused by the grazing incidence of soft x-ray light on the concave grating. The spectral and spatial resolutions of the spectrometer are calculated by applying the wave front aberration theory, and the diffraction efficiency is calculated by applying the scalar diffraction theory.

• Journal of the Optical Society of Korea
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• v.17 no.4
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• pp.312-316
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• 2013

A novel fiber-optic sensor system is suggested in which fiber Bragg grating sensors are demodulated by a wavelength-sweeping fiber laser source and a spectrometer. The spectrometer consists of a diffraction grating and a 512-pixel photo-diode array. The reflected Bragg wavelength information is transformed into spatial intensity distribution on the photo-diode array. The peak locations linearly correspond to the Bragg wavelengths, regardless of the nonlinearities in the wavelength tuning mechanism of the fiber laser. The high power density of the fiber laser enables obtaining high signal-to-noise ratio outputs. The improved demodulation characteristics were experimentally demonstrated with a fiber Bragg grating sensor array with 5 gratings. The sensor outputs were in much more linear fashion compared with the conventional tunable band-pass filter demodulation. Also it showed advantages in signal processing, due to the high level of photo-diode array signals, over the broadband light source system, especially in measurement of fast varying dynamic physical quantities.

• Current Optics and Photonics
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• v.1 no.4
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• pp.295-307
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• 2017

An innovative system for the alternative continuous wide spectral spatial heterodyne spectrometer (ACWS-SHS) is proposed. The relationship between the ACWS-SHS and the wide spectral spatial heterodyne spectrometer (WS-SHS) at the resolution limit, the spectral range, the grating diffraction efficiency and the interference fringes contrast ratio has been analyzed theoretically. Through the comparison of the theoretical analysis and simulation results, it is found that the two systems for the WS-SHS and the ACWS-SHS have the same resolution limit and spectral range, which are ${\delta}{\sigma}$ and ${\sigma}_{01}$, while in the ACWS-SHS system the critical diffraction efficiency of echelle grating is 68.39% and the critical contrast ratio of interference fringes is 0.4135, which is much better than the performance of the WS-SHS system. Therefore, the ACWS-SHS reduces the high requirements for the precision of equipment and expands the application field of SHS effectively.

• Journal of Sensor Science and Technology
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• v.26 no.1
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• pp.28-34
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• 2017

An NIR grism Si optical area sensor spectrometer with in-band reference wavelength is designed and fabricated. It is composed of a transmission type diffraction grating (spatial density 300 line/mm), a rectangular N-BK7 prism (apex angle 30 degree), NIR filter(cutoff wavelength 720 nm), an imaging convex lens(focal length 50 mm F1.8) and an IR modified DSLR camera (Canon EOS40D) of Si optical area sensor ($3,888{\times}2,592$ pixels, pixel size $5.710{\mu}m$). "In-band reference wavelength function" is implemented using non-dispersive 0th diffraction order optical beam. The NIR grism spectrometer is tested in a laboratory using a halogen lamp and a Neon lamp. And the spectrometer is used in an astronomy field for obtaining the planet Jupiter NIR spectrum. In-band reference wavelength i.e. un-deviation wavelength is 846 nm, an wavelength resolution is 0.3027 nm/pixel, an wavelength resolving power is 2,794 and an wavelength range is 650~1,000 nm.

• Journal of the Optical Society of Korea
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• v.20 no.6
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• pp.669-677
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• 2016

A miniaturized FTIR spectrometer based on lamellar grating interferometry is being developed for passive remote-sensing. Consisting of a pair of micro-mirror arrays, the lamellar grating can be fabricated using MEMS technology. This paper describes a method to compute the optical field in the interferometer to optimize the design parameters of the lamellar grating FTIR spectrometer. The lower limit of the micro-mirror width in the grating is related to the formation of a Talbot image in the near field and is estimated to be about $100{\mu}m$ for the spectrometer to be used for the wavelength range of $7-14{\mu}m$. In calculating the far field at the detection window, the conventional Fraunhofer equation is inadequate for detection distance of our application, misleading the upper limit of the micro-mirror width to avoid interference from higher order diffractions. Instead, the far field is described by the unperturbed plane-wave combined with the boundary diffraction wave. As a result, the interference from the higher order diffractions turns out to be negligible as the micro-mirror width increases. Therefore, the upper limit of the micro-mirror width does not need to be set. Under this scheme, the interferometer patterns and their FT spectra are successfully generated.

• Journal of Biomedical Engineering Research
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• v.11 no.1
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• pp.19-24
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• 1990

A simple diffraction grating spectrometer is successfully utilized to distinguish the similar red colored sediments obstained from both of cancer and non-cancer urine reactions caused by the the previous developed reagent for the cancer diagnosis by examining their spectral absorption bands in order to improve its sensitivity and specficity. It is found that the cancer and non-cancer absorp- tion band regions lie between 4250 A and 4750 A and between 5250 A and 5400 A, respectively.

• Journal of the Korean Chemical Society
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• v.49 no.6
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• pp.584-590
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• 2005