• Title, Summary, Keyword: Diffraction grating

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Spectral Analysis of Arrayed Waveguide Grating (Arrayed Waveguide Grating의 스펙트럼해석)

  • Jung, Jae-Hoon
    • Journal of IKEEE
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    • v.8 no.1
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    • pp.121-127
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    • 2004
  • We performed the spectrum analysis of arrayed waveguide grating using Fresnel Kirchhoff diffraction formula and its approximated Fraunhofer diffraction equation and applied both methods to 16 channel and 40 channel models. We presented the spectra and found out the limitations of Fraunhofer diffraction in analysis of arrayed waveguide grating and compared the errors coming from Fraunhofer diffraction approximation and due to imperfection during the fabrication process.

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Analysis on Design and Fabrication of High-diffraction-efficiency Multilayer Dielectric Gratings

  • Cho, Hyun-Ju;Lee, Kwang-Hyun;Kim, Sang-In;Lee, Jung-Hwan;Kim, Hyun-Tae;Kim, Won-Sik;Kim, Dong Hwan;Lee, Yong-Soo;Kim, Seoyoung;Kim, Tae Young;Hwangbo, Chang Kwon
    • Current Optics and Photonics
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    • v.2 no.2
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    • pp.125-133
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    • 2018
  • We report an in-depth analysis of the design and fabrication of multilayer dielectric (MLD) diffraction gratings for spectral beam combining at a wavelength of 1055 nm. The design involves a near-Littrow grating and a modal analysis for high diffraction efficiency. A range of wavelengths, grating periods, and angles of incidence were examined for the near-Littrow grating, for the $0^{th}$ and $-1^{st}$ diffraction orders only. A modal method was then used to investigate the effect of the duty cycle on the effective indices of the grating modes, and the depth of the grating was determined for only the $-1^{st}$-order diffraction. The design parameters of the grating and the matching layer thickness between grating and MLD reflector were refined for high diffraction efficiency, using the finite-difference time-domain (FDTD) method. A high reflector was deposited by electron-beam evaporation, and a grating structure was fabricated by photolithography and reactive-ion etching. The diffraction efficiency and laser-induced damage threshold of the fabricated MLD diffraction gratings were measured, and the diffraction efficiency was compared with the design's value.

Direct writing of multi-layer diffraction grating inside fused silica glass by using a femtosecond laser (펨토초 레이저를 이용한 실리카 내부의 다층 회절격자 가공 기술)

  • Choi, Hun-Kook;Kim, Jin-Tae;Sohn, Ik-Bu;Noh, Young-Chul
    • Laser Solutions
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    • v.14 no.3
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    • pp.17-20
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    • 2011
  • We fabricated a multi-layer diffraction grating inside fused silica glass by using a femtosecond laser direct writing method. The femtosecond laser with a wavelength of 515 nm, a pulse width of 250 fs, a repetition rate of 100 kHz, and an average output power of 6 W was used. Two layer diffraction grating with a grating period of $6{\mu}m$ was successfully fabricated with the layer gap of 0.5, 1, 2, 3, and $5{\mu}m$, respectively. Also, we investigated the diffraction pattern by illuminating a He-Ne laser beam. Finally, we demonstrated the diffraction grating with a grating period of $3{\mu}m$ by adjusting the gap of each layer with a grating period of $6{\mu}m$. Femtosecond laser direct writing technology of multi-layer has a potential to fabricate the diffraction grating with a grating period of below $1.5{\mu}m$.

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Fabrication and improvement of diffraction grating with femtosecond and $CO_2$ laser (레이저를 이용한 회절격자 제작 및 효율 향상 연구)

  • Choi, Hun-Kook;Sohn, Ik-Bu;Noh, Young-Chul;Kim, Jin-Tae
    • Laser Solutions
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    • v.15 no.2
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    • pp.6-10
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    • 2012
  • We fabricated the diffraction grating on the surface of fused silica glass using a femtosecond laser. The grooves of diffraction grating has a lot of micro crack and debris result in reduced diffraction efficiency. So, we polished the diffraction grating with $CO_2$ laser beam. With different scan number of $CO_2$ laser beam, we observed the image of diffraction grating and measured the diffraction efficiency.

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Fabrication of a Polymeric Planar Nano-diffraction Grating with Nonuniform Pitch for an Integrated Spectrometer Module (집적화된 분광모듈 구현을 위한 고분자 기반의 비등간격 평면나노회절격자 제작)

  • Kim, Hwan-Gi;Oh, Seung-Hun;Choi, Hyun-Yong;Park, Jun-Heon;Lee, Hyun-Yong
    • 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.

Holographic Data Grating Formation of AsGeSeS Single & Ag/AsGeSeS Double Layer Thin Films with the Incident Beam Wavelength (입사빔의 파장에 따른 AsGeSes & Ag/AsGeSes 박막의 홀로그래픽 데이터 소거특성)

  • Koo, Yong-Woon;Chung, Hong-Bay
    • Proceedings of the KIEE Conference
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    • pp.1428-1429
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    • 2006
  • We investigated the diffraction efficiency, erasing property and rewriting property of diffraction grating with each wavelength of recording beam. A (P:P) polarized light was exposed on AsGeSeS and Ag/AsGeSeS thin film to form a diffraction grating by HeNe(635nm) laser and DPSS(532nm) laser. At the maximum efficiency condition, unpolarized HeNe laser beam was irradiated to erase 1ha generated diffraction grating. The HeNe laser showed more higher diffraction efficiency and the DPSS laser showed more faster diffraction grating time. At erasing and rewriting process, AsGeSeS(61%-85%)thin film showed better property than Ag doped Ag/AsGeSeS(53%-63%) double layer structured thin film.

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Spatial Frequency Filtering Characteristics of Annular Phase Gratings (고리형 위상 격자의 공간 주파수 필터 효과)

  • 김인길;고춘수;임성우;오용호;이재철
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.17 no.9
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    • pp.994-1000
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    • 2004
  • We studied the characteristics of annular phase gratings as spatial frequency filters. We first calculated the Fraunhofer diffraction patterns of annular gratings and then got the modulation transfer function (MTF) from the zeroth order Hankel transform of the intensity distribution function. Binaryphase annular grating shows higher diffraction efficiency than binary phase rectangular grating. But the MTF decreases linearly in the low-frequency region as that of rectangular grating does. The diffraction pattern of 4-phase annular grating is similar to that of 2-phase grating and hence MTFs of the two are much alike. For 8-phase annular grating, the 7th order diffracted beam is the lowest one next to the first. Consequently, the diffraction efficiency is very high and the MTF graph is curved upward. The diffracted beams except the first order are negligible and hence the MTF characteristics are more improved in the case of 16-phase grating. But the degree of improvement becomes lowered c(Impaled with 8-phase grating. We made a 16-phase annular grating and measured its MTF. The experimental result agrees well with the calculated one.

Symmetry Exploitation of Diffraction Gratings to Enhance the Spectral Resolution

  • Lee, Eun-Seong;Lee, Jae-Yong
    • 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.

Diffraction grating interferometer for null testing of aspheric surface with binary amplitude CGH (이진 컴퓨터 형성 홀로그램을 이용한 비구면 형상 측정용 위상편이 회절격자 간섭계)

  • 황태준;김승우
    • Korean Journal of Optics and Photonics
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    • v.15 no.4
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    • pp.313-320
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    • 2004
  • We present a null testing method fer aspheric surfaces, utilizing a phase-shifting diffraction grating interferometer along with a binary amplitude computer generated hologram (CGH). The binary amplitude CGH is designed to compensate for the wavefront between a point source and the aspheric surface under test. The fringe visibility of the grating interferometer is controlled easily by selecting suitable grating diffraction orders for the measurement and reference wavefronts or by optimizing the groove shape of the grating used. The binary amplitude CGH is designed by numerical analysis of ray tracing and fabricated using e-beam lithography for autostigmatic testing. Experimental results of a large-scale aspheric mirror surface are discussed to verify the measurement performance of the proposed diffraction grating interferometer.

2- Dimensional Embossing Type Hologram Fabrication in Amorphous As-Ge-Se-S with the Selective Etching (비정질 As-Ge-Se-S 박막에서 선택적 에칭을 통한 2차원 엠보싱형 홀로그램 제작)

  • Lee, Ki-Nam;Chung, Hong-Bay
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.55 no.7
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    • pp.354-358
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    • 2006
  • In this paper, we investigated the selective etching rate of amorphous As-Ge-Se-S thin film due to the photoexpansion effect and fabricated the 2-dimensional embossing type diffraction grating hologram. We measured the thickness change with the etching time among NaOH solution after forming 1-dimension diffraction grating. As a results, we found that the selective etching rate were $2.5\AA/s,\;3.3\AA/s,\;3.9\AA/s$ where NaOH solution concentration were 0.26N, 0.33N, 0.36N, respectively. Also after the formation of 2-dimensional diffraction grating by the $90^{\circ}$ degree of circulation on the formed 1-dimensional diffraction grating, we etched selectively during 60sec, among 0.26N NaOH solution and obtained 2-dimensional embossing diffraction grating. As the results of AFM (Atomic Force Microscopy), we confirmed the formation of distinct embossing type 2-dimensional diffraction grating hologram, successfully.