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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Korean Journal of Optics and Photonics
Journal Basic Information
Journal DOI :
Optical Society of Korea
Editor in Chief :
Volume & Issues
Volume 20, Issue 6 - Dec 2009
Volume 20, Issue 5 - Oct 2009
Volume 20, Issue 4 - Aug 2009
Volume 20, Issue 3 - Jun 2009
Volume 20, Issue 2 - Apr 2009
Volume 20, Issue 1 - Feb 2009
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Automatic Gain Flattening Control and Automatic Gain Control Using an All Optical Method in an Optical Amplifier
Choi, Bo-Hun ; Lee, Sang-Soo ;
Korean Journal of Optics and Photonics, volume 20, issue 5, 2009, Pages 261~265
DOI : 10.3807/KJOP.2009.20.5.261
Our amplifier using an all optical method and a fixed GFF achieved automatic gain flatness throughput the C-band without any NF degradation, and simultaneously achieved a constant 25 dB gain, while input signals were varied between one channel and forty WDM channels. When thirty nine channels were added and dropped, the transient gain variation of the survival channel was not greater than the steady-state gain variation, and its wavelength dependency was negligible.
Design of Thermo-optic Switch with Low Power Consumption by Electrode Optimization
Choi, Chul-Hyun ; Kong, Chang-Kyeng ; Lee, Min-Woo ; Sung, Jun-Ho ; Lee, Seung-Gol ; Park, Se-Geun ; Lee, El-Hang ; O, Beom-Hoan ;
Korean Journal of Optics and Photonics, volume 20, issue 5, 2009, Pages 266~271
DOI : 10.3807/KJOP.2009.20.5.266
We designed a thermo-optic switch based on a directional coupler with not only a high extinction ratio but also significantly low power consumption. The switch operates by using the thermo-optic effect of the polymer which the refractive index changes by heating the electrode. If the electrode is not powered (OFF), the input light will be coupled completely to the other waveguide. When the electrode is powered at a certain level (ON), input light launched into the input waveguide will remain in that waveguide due to the lower index adjusted in the other waveguide. The switch based on the directional coupler was designed using the generalized extinction ratio curve and the lateral shift of the input waveguide. The coupling length is 1,610
and the extinction ratios are -28 and -30 dB for ON and OFF states, respectively. The electrode structures were optimized by thermal analysis. The transported heat into the waveguide is increased, as the electrode width (w) is increased and the center distance between the electrode and the waveguide (d) is decreased. Also, because the heat generated in the electrode affects the other waveguide, the temperature difference between two waveguides is varied as the given w and d. There are specific conditions which have the maximum of the temperature difference. That of the temperature difference is increased as the width and the temperature of the electrode are increased. Especially, when the switch is designed using the condition with the maximum of the temperature difference for switching, the temperature of the electrode can be decreased. We expect this condition will be the novel method for the reduction of the power consumption in a thermo-optic switch.
Interference Fringe Signal Filtering Method for Performance Enhancing of White Light Interfrometry
Yim, Hae-Dong ; Lee, Min-Woo ; Lee, Seung-Gol ; Park, Se-Geun ; Lee, El-Hang ; O, Beom-Hoan ;
Korean Journal of Optics and Photonics, volume 20, issue 5, 2009, Pages 272~275
DOI : 10.3807/KJOP.2009.20.5.272
In order to enhance the background noise filtering performance of the white light interferometry(WLI), we demonstrate the noise filtering performance of preprocessing of the measured fringe signals. The WLI was realized through a mirau interferometer which was equipped with a green LED. When measuring large-height and rough surface objects, the illumination optics are considered the numerical aperture(NA) and the depth of focus(DOF). In this case, the limited NA of the illumination optics has a considerable impact on the interference fringe. Therefore, we propose a preprocessing method that uses the intensity difference between the measured intensity and the moving average intensity. The performance is demonstrated by measuring an array of metal solder balls fabricated on printed circuit board(PCB). The proposed method reduces the noise pixels by 15 percent.
Stabilization of Output Pulses from a Passively Q-switched Nd:YVO
Laser Pumped by a Continuous-wave Laser Diode
Ahn, Seung-In ; Park, Yune-Bae ; Yeo, Hwan-Seop ; Lee, Joon-Ho ; Lee, Kang-In ; Yi, Jong-Hoon ;
Korean Journal of Optics and Photonics, volume 20, issue 5, 2009, Pages 276~280
DOI : 10.3807/KJOP.2009.20.5.276
A Cr:YAG crystal was used as a saturable absorber for passive Q-switching of a Nd:
laser which was pumped by a 1-W continuous wave laser diode. The first surface of the Cr:YAG was high-reflection coated for the pump wavelength. The high-reflection coating improved the absorption efficiency of the pump beam in the Nd:
through double pass absorption. It also prevented pump beam induced partial bleaching of the Cr:YAG. The peak-to-peak pulse fluctuation of passively Q-switched laser output was approximately 4 %. The minimum pulse-width was measured to be 7.11 ns. Also, the average pulse repetition rate was 9 kHz and the maximum output power was 16.27 mW.
Precise Measurement of Optical Anisotropy of Rubbed Polyimide on Patterned Glass and its Nanoscale Variation
Kim, Ha-Rang ; Kim, Sang-Youl ;
Korean Journal of Optics and Photonics, volume 20, issue 5, 2009, Pages 281~287
DOI : 10.3807/KJOP.2009.20.5.281
The optical anisotropy of rubbed PI(polyimide) film on patterned LCD glass substrate is analyzed using polarimetry. The direction of the optic axis and the magnitude of the very small retardation (
0.4 nm or less) is precisely measured by using a transmission ellipsometer. The variation of the optical anisotropy is presented as the curve of the optic axis versus the magnitude of the phase retardation and it is explained by using a simple optical model.
Analysis of Effective Optic Axis and Equivalent Retardation of Composite Optically Anisotropic Film by Using Transmission Ellipsometry
Ryu, Jang-Wi ; Kim, Sang-Youl ;
Korean Journal of Optics and Photonics, volume 20, issue 5, 2009, Pages 288~293
DOI : 10.3807/KJOP.2009.20.5.288
Polarization characteristics of a composite film composed of two optically anisotropic films are analyzed. The procedure to determine the effective optics axis and the equivalent retardation of the composite film is suggested in conjuction with the related ellipsometric expressions. The explicit expressions of the effective optic axis and the equivalent retardation of a non-uniform anisotropic film are derived when all optic axes are parallel. Those expressions of the composite film where optic axes of two constituting anisotropic films are not parallel are also derived. Dependence of those expressions on the polarization state of the incident light or the azimuth angle of the linearly polarized light and their limit when applied to practical use are discussed.
Four-leaf Clover-shaped Antenna for THz Photomixer for High Output Power
Woo, In-Sang ; Nguyen, Truong Khang ; Park, Ik-Mo ; Lim, Han-Jo ; Han, Hae-Wook ; Chu, Hong ;
Korean Journal of Optics and Photonics, volume 20, issue 5, 2009, Pages 294~300
DOI : 10.3807/KJOP.2009.20.5.294
To improve the output power of a photomixer as a THz source, we propose a four-leaf clover-shaped antenna structure which is composed of a highly resonant radiation element and a stable DC feed element. The resonance characteristics of the proposed structure were investigated on a half-infinite substrate first as a simplified radiation environment in order to save the computation time. Based on the antenna characteristics on a half-infinite substrate, the antenna structure was designed to have a maximum total efficiency and a maximum directivity on an extended hemispherical lens. In comparison with a full-wavelength dipole, an input resistance of this structure increased six fold and this characteristic significantly improved the mismatch efficiency between a photomixer and an antenna. THz output power from this structure is expected to increase by 2.7 times as compared to a full-wavelength dipole case.
Self-aligning Characteristics of Optical Sheets with Apertures
Park, Gyeung-Ju ; Kim, Young-Gyu ; Choi, Gye-Hun ; Baik, Sang-Hoon ; Hwang, Sung-Ki ; Gwag, Jin-Seog ; Yi, Jong-Hoon ; Kwon, Jin-Hyuk ; Park, Yi-Soon ;
Korean Journal of Optics and Photonics, volume 20, issue 5, 2009, Pages 301~307
DOI : 10.3807/KJOP.2009.20.5.301
Optical sheets with apertures on the opposite side of the substrate are designed and analyzed in order to use them as high efficiency light concentration sheets in LCD edge-lit backlight. Formation of apertures by self-aligning exposure were analyzed for the microlens array sheet, pyramid array sheet, and cone array sheet and the microlens array sheet showed the best performance for the formation of apertures by the self-aligning exposure.