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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Optical Society of Korea
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Journal DOI :
Optical Society of Korea
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Volume & Issues
Volume 16, Issue 4 - Dec 2012
Volume 16, Issue 3 - Sep 2012
Volume 16, Issue 2 - Jun 2012
Volume 16, Issue 1 - Mar 2012
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Alternative Method of AWG Phase Measurement Based on Fitting Interference Intensity
Oh, Yong Ho ; Lim, Sungwoo ; Go, Chun Soo ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 91~94
DOI : 10.3807/JOSK.2012.16.2.091
Arrayed waveguide grating (AWG) phase errors are normally assessed from the Fourier transform of the interference intensity data in the frequency domain method. However it is possible to identify the phases directly from the intensity data if one adopts a trial-and-error method. Since the functional form of the intensity profile is known, the intensities can be calculated theoretically by assuming arbitrary phase errors. Then we decide the phases that give the best fit to the experimental data. We verified this method by a simulation. We calculated the intensities for an artificial AWG which is given arbitrary phases and amplitudes. Then we extracted the phases and amplitudes from the intensity data by using our trial-and-error method. The extracted values are in good agreement with the originally given values. This approach yields better results than the analysis using Fourier transforms.
Functional Relation Between Signal Distortion and a Figure of Merit for Nonlinear Process in Dispersion-managed Optical Transmission
Kim, Sungman ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 95~100
DOI : 10.3807/JOSK.2012.16.2.095
We show that the minimum EOP (eye-opening penalty) obtained by tunable dispersion compensation is a function of a figure of merit for a nonlinear process,
is the optical intensity and
is the effective length of the interaction region. Using this rule, we do not need to conduct nonlinear simulations in all the cases of signal power and transmission length to obtain the signal distortion in dispersion-managed optical transmission. Instead, we need to conduct a simulation in only one case of a signal power and find the functional relation, and then we can obtain the values of the signal distortion in other cases using the discovered functional relation. This technique can reduce the number of nonlinear simulations to less than 10%.
1.25 Gb/s Broadcast Signal Transmission in WDM-PON Based on Mutually Injected Fabry-Perot Laser Diodes
Yoo, Sang-Hwa ; Mun, Sil-Gu ; Kim, Joon-Young ; Lee, Chang-Hee ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 101~106
DOI : 10.3807/JOSK.2012.16.2.101
We demonstrate a cost effective broadcast signal transmission at 1.25-Gb/s with 100 GHz channel spacing based on a broadband light source (BLS) for a wavelength division multiplexing-passive optical network (WDM-PON). The BLS is implemented by using mutually injected Fabry-Perot laser diodes (MI F-P LDs). The error-free transmission without a forward error correction (FEC) is achieved by its low relative intensity noise (RIN). The number of usable modes is determined by RIN and/or extinction ratio (ER) in the spectrum sliced light output.
Multi-coded Variable PPM for High Data Rate Visible Light Communications
Moon, Hyun-Dong ; Jung, Sung-Yoon ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 107~114
DOI : 10.3807/JOSK.2012.16.2.107
In this paper, we propose a new modulation scheme called multi-coded variable pulse position modulation (MC-VPPM) for visible light communication systems. Two groups of signals (Pulse Width Modulation (PWM) and Pulse Position Modulation (PPM) groups) are multi-coded by orthogonal codes for transmitting data simultaneously. Then, each multi-level value of the multi-coded signal is converted to pulse width and position which results in not only an improved data rate, but also a processing gain in reception. In addition, we introduce average duty ratio and cyclic shift concepts in PWM through which dimming control for light illumination can be supported without any degradation in communication performance. Through simulation, we confirm that the proposed MC-VPPM shows a comparable BER curve and much greater achievable data rate than the conventional VPPM scheme using a visible light optical channel environment.
Statistical Analysis of 3D Volume of Red Blood Cells with Different Shapes via Digital Holographic Microscopy
Yi, Faliu ; Lee, Chung-Ghiu ; Moon, In-Kyu ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 115~120
DOI : 10.3807/JOSK.2012.16.2.115
In this paper, we present a method to automatically quantify the three-dimensional (3D) volume of red blood cells (RBCs) using off-axis digital holographic microscopy. The RBCs digital holograms are recorded via a CCD camera using an off-axis interferometry setup. The RBCs' phase image is reconstructed from the recorded off-axis digital hologram by a computational reconstruction algorithm. The watershed segmentation algorithm is applied to the reconstructed phase image to remove background parts and obtain clear targets in the phase image with many single RBCs. After segmenting the reconstructed RBCs' phase image, all single RBCs are extracted, and the 3D volume of each single RBC is then measured with the surface area and the phase values of the corresponding RBC. In order to demonstrate the feasibility of the proposed method to automatically calculate the 3D volume of RBC, two typical shapes of RBCs, i.e., stomatocyte/discocyte, are tested via experiments. Statistical distributions of 3D volume for each class of RBC are generated by using our algorithm. Statistical hypothesis testing is conducted to investigate the difference between the statistical distributions for the two typical shapes of RBCs. Our experimental results illustrate that our study opens the possibility of automated quantitative analysis of 3D volume in various types of RBCs.
Horizontal-parallax-only Optical Scanning Holography with an Electronic Low-pass Filter
Kim, Taegeun ; Jang, Sun Ho ; Kim, You Seok ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 121~126
DOI : 10.3807/JOSK.2012.16.2.121
We propose a novel technique that records the horizontal-parallax-only (HPO) hologram of a real object using optical scanning holography (OSH). The proposing HPO-OSH is composed of a conventional OSH and an electronics low pass filter. When we scan an object along vertical direction before horizontal direction, the electronic low pass filter filters the vertical fringes with preserving horizontal fringes and gives an HPO hologram. To the best of our knowledge, this is the first time to record the HPO hologram using OSH without either truncation of the scanning beam or digital post processing.
Forming a Fresnel Zone Lens: Effects of Photoresist on Digital-micromirror-device Maskless Lithography with Grayscale Exposure
Huang, Yi-Hsiang ; Jeng, Jeng-Ywan ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 127~132
DOI : 10.3807/JOSK.2012.16.2.127
This study discusses photoresist forming using a composite grayscale to fabricate a Fresnel lens. Grayscale lithography is a common production method used to facilitate the forming of lenses with different curvatures and depths. However, this approach is time consuming and expensive. This study proposes a method for overcoming these obstacles by integrating a digital micromirror device and microscope to supplant the traditional physical grayscale mask. This approach provides a simple and practical maskless optical lithography system. According to the results, the two adjacent grayscales displayed substantial differences between the high grayscale and influence the low grayscale that ultimately affected photoresist formation. Furthermore, we show that change of up to 150% in the slope can be achieved by changing the grayscale gradient in the central zone and the ring profile. The results of the optical experiment show a focus change with different gray gradients.
The Application of Optical Coherence Tomography in the Diagnosis of Marssonina Blotch in Apple Leaves
Lee, Changho ; Lee, Seung-Yeol ; Jung, Hee-Young ; Kim, Jeehyun ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 133~140
DOI : 10.3807/JOSK.2012.16.2.133
In this study we investigate the use of 2D and 3D scanning optical coherence tomography (OCT) technology for use in apple blotch diagnosis. In order to test the possible application of OCT as a detection tool for apple trees affected by Marssonina coronaria, we conducted several experiments and compared the results from both healthy and infected leaves. Using OCT, we found several distinctive features in the subsurface boundary regions of both the diseased and healthy leaves. Our results indicate that leaves from diseased trees, while still appearing healthy, can be affected by M. coronaria. The A-scan analysis method confirmed that the boundaries found under the subsurface layers can be faint. This shows that M. coronaria can exert its influence on entire apple trees (as opposed to only on leaves with lesions) once it infects healthy trees. Our results indicate that OCT can be used as a noninvasive tool for the diagnosis of fungal disease in apple trees. Microscopic imaging results, performed as a histological study for comparison, correlated well with the OCT results.
Low Stratospheric Wind Measurement Using Mobile Rayleigh Doppler Wind LIDAR
Shu, Zhi-Feng ; Dou, Xian-Kang ; Xia, Hai-Yun ; Sun, Dong-Song ; Han, Yan ; Cha, Hyunki ; Kim, Dukhyeon ; Wang, Guo-Cheng ; Baik, Sunghoon ; Hu, Dong-Dong ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 141~144
DOI : 10.3807/JOSK.2012.16.2.141
A mobile Rayleigh Doppler wind LIDAR at an eye-safe wavelength of 355 nm incorporating double-edge technique with triple-channel Fabry-Perot etalon is developed for wind measurement from 5 to 40km. The structure of this LIDAR system is described. An intercomparsion experiment with rawinsonde is made, showing good agreement with expected measurement accuracy. A continuous observation of stratosphere wind field for several days with temporal resolution of 15 min and spatial resolution of 200 m from 5 to 40 km is presented, demonstrating the stability and robustness of the LIDAR. A stratospheric quasi-zero wind layer can be found at around 20 km with a direction change from east to west evident in the continuous observation.
A Display-based Visual Stimulator for Psychophysical and Electrophysiological Color Sensitivity Measurements
Hwang, Jisoo ; Park, Seung-Nam ; Park, Cheol-Min ; Lee, Geun Woo ; Kim, Kiseong ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 145~150
DOI : 10.3807/JOSK.2012.16.2.145
We present a display-based visual stimulator for psychophysical and electrophysiological visual sensitivity measurements. The stimulator offers various psychophysical visual stimuli and transfers the signals from external devices along with the stimulation signals to an electrophysiological recorder. As an experimental demonstration, we perform a visual sensitivity experiment in the mesopic vision range by using the display-based stimulator. The intensity of the steady-state visual evoked potential is observed to correlate with the luminance of the flickering visual stimulation. For the psychophysically determined detection thresholds, we determine the mesopic luminance, showing agreement with the perceived brightness within the uncertainty of the luminance measurement.
Experimental and Simulation Study of the Optical Performances of a Wide Grid Polarizer as a Luminance Enhancement Film for LCD Backlight Applications
Seo, Jae Seok ; Yeom, Tae Eun ; Ko, Jae-Hyeon ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 151~156
DOI : 10.3807/JOSK.2012.16.2.151
Reflective polarizers can be used as luminance enhancement films for LCD backlights via the polarization recycling process. The optical performances of a wire grid polarizer (WGP) as a reflective polarizer adopted in edge-lit backlights were investigated by luminance evaluation and a time-domain simulation technique. The results were compared to those of a commercial dielectric multilayer film. The luminance gain factor of WGP was smaller than that of the multilayer film by 18%. This was attributed to a much larger internal loss of WGP due to light absorption by metal wires. The internal losses of both reflective polarizers and the polarization conversion efficiency of the backlight were obtained numerically based on a phenomenological model. The optical performances of WGP were optimized by using a time-domain simulation technique. The luminance gain increased and was found to become comparable to, but slightly less than the case of the dielectric multilayer film with decreasing line width.
Single Mode Lasing in InGaAsP/InP Semiconductor Coupled Square Ring Cavities
Hyun, Kyung-Sook ; Lee, Taekyu ; Moon, Hee-Jong ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 157~161
DOI : 10.3807/JOSK.2012.16.2.157
This work reports the stability of the resonant characteristics in multimode interferometer coupled square ring semiconductor cavities. Based on the analysis of single square ring cavities, the single mode operations in the multimode interferometer coupled ring cavities are analyzed and the devices are demonstrated on the semiconductor multiple quantum well epitaxial structure. By varying the lasing conditions such as substrate temperature and input pump power, single resonant mode operations are also observed.
Bow-tie Mode Lasing in a Grooved Rectangular Semiconductor Microcavity
Moon, Hee-Jong ; Hyun, Kyung-Sook ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 162~165
DOI : 10.3807/JOSK.2012.16.2.162
Bow-tie modes were proposed in a grooved rectangular resonator and their lasing characteristics were investigated in semiconductor microcavities. The observed spacing between two adjacent lasing peaks from the grooved cavity was reduced compared to that of 4-bounce whispering gallery modes (WGMs) from the same-sized simple rectangular cavity due to increased round-trip path length of the bow-tie modes. The lasing spectra of bow-tie modes obtained from two adjacent corners showed highly correlated patterns while those of 4-bounce WGMs did not.
High-transmittance Multi-domain Vertical Alignment Liquid Crystal Device with Protrusion Structure
Kim, Ki-Han ; Jeon, Eun-Young ; Park, Byung Wok ; Choi, Sun-Wook ; Song, Dong Han ; Kim, Hoon ; Shin, Ki-Chul ; Kim, Hee Seop ; Yoon, Tae-Hoon ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 166~169
DOI : 10.3807/JOSK.2012.16.2.166
We propose a high-transmittance multi-domain vertical alignment liquid crystal device with a protrusion structure. Disclination lines, which inevitably appear at the boundaries of domains in a multi-domain structure, can be reduced by adding a protrusion structure on the top substrate. The transmittance was improved by 11% using the proposed structure with no change of either the dark state or the operating voltage.
Formation of Dual Threshold in a Vertical Alignment Liquid Crystal Device
Choi, Sun-Wook ; Jin, Huilian ; Kim, Ki-Han ; Lee, Ji-Hoon ; Kim, Hoon ; Shin, Ki-Chul ; Kim, Hee Seop ; Yoon, Tae-Hoon ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 170~173
DOI : 10.3807/JOSK.2012.16.2.170
We present a method that enables dual threshold voltages in a vertical alignment liquid crystal device, through which the gamma shift can be reduced with no subsequent decrease in the contrast ratio. By forming polymer layers, the threshold voltage shift is accomplished through the utilization of the voltage drop effect. We expect that the proposed method can be applied to the conventional 4-domain mode in order to achieve an 8-domain mode without the need for complex driving schemes.
Investigation of the Performance of Spectral Domain Optical Doppler Tomography with High-speed Line Scanning CMOS Camera and Its Application to the Blood Flow Measurement in a Micro-tube
Park, Cheol Woo ; Lee, Changho ; Lim, SooHee ; Ni, Aleksey ; An, Jin Hyo ; Lee, Ho ; Bae, Jae Sung ; Kim, Jeehyun ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 174~180
DOI : 10.3807/JOSK.2012.16.2.174
In this study, the feasibility of spectral domain optical Doppler tomography for measuring blood flow characteristics in a micro-tube was demonstrated through several experiments. The use of an SD-ODT system in blood flow measurement can provide high resolution images (5 microns resolution). We prepared three capillary tubes to reveal the effect of different concentrations of hematocrit ratio (HR). One tube serves as the control. The two other tubes contained different concentrations of HR (5%, 25%). Three different capillary tube inlet flow velocities were tested in the present study. The Reynolds number (Re) which is based on the capillary tube inner diameter ranges from Re=6 to 48. We calculated a Doppler shift of the power spectrum of the temporal interference fringes with Kasai autocorrelation function to achieve the velocity profile of the flow. As a result, SD-ODT systems could not detect the cell depletion layer in the present study due to the limitation of spatial resolution. Nevertheless, these systems were proven to be capable of observing the RBCs of blood.
Frequency Dependency of Multi-layer OLED Current Density-voltage Shift and Its Application to Digitally-driven AMOLED
Kim, Hyunjong ; Kim, Suhwan ; Hong, Yongtaek ;
Journal of the Optical Society of Korea, volume 16, issue 2, 2012, Pages 181~184
DOI : 10.3807/JOSK.2012.16.2.181
We report, for the first time, operation frequency dependence of current density-voltage (
) shift for multi-layer organic light-emitting diodes (OLEDs). When the OLEDs were electrically stressed for 21 hours with 50% duty voltage pulses at 60, 120, 240, and 360 Hz, the JOLED-VOLED shifts were suppressed by half for 360 Hz operation compared with 60 Hz operation, but with little change in emission efficiencies. This frequency dependent
shift is believed to be commonly observed for typical multi-layer OLEDs and can be used to further improve lifetime of digitally-driven active-matrix OLED displays.