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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 18, Issue 6 - Dec 2014
Volume 18, Issue 5 - Oct 2014
Volume 18, Issue 4 - Aug 2014
Volume 18, Issue 3 - Jun 2014
Volume 18, Issue 2 - Apr 2014
Volume 18, Issue 1 - Feb 2014
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Ultra Broadband Absorption of SPPs Enhanced Dual Grating Thin Film CIGS Solar Cell Enabled by Particle Swarm Optimization
Le, DuyKhanh ; Tran, QuyetThang ; Lee, Sangjun ; Kim, Sangin ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 429~435
DOI : 10.3807/JOSK.2014.18.5.429
We examined the effective utilization of Particle Swarm Optimization (PSO) to enhance the light absorption performance in thin CuIn1-xGaxSe2 (CIGS) solar cells with dual (top and bottom) gratings. The PSO tuned structure was demonstrated to be capable of achieving high and ultra broadband absorption spectra due to well-spaced and well-defined absorption peaks, which were SPPs and photonic modes induced by the metal and dielectric gratings. For only TM polarization and both polarizations, the fully optimized net absorptions exhibit 85.6% and 78.1%, which correspond to ~35.4% and ~23.5% improvement compared to optimized flat structures, respectively.
Colorless Amplified WDM-PON Employing Broadband Light Source Seeded Optical Sources and Channel-by-Channel Dispersion Compensators for >100 km Reach
Kang, Byoung-Wook ; Lee, Kwanil ; Lee, Sang Bae ; Kim, Chul Han ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 436~441
DOI : 10.3807/JOSK.2014.18.5.436
We have demonstrated an amplified wavelength-division multiplexed (WDM) passive optical network (PON) by using broadband light source (BLS) seeded optical sources and chirped fiber Bragg gratings (FBGs) based dispersion compensators. Chirped FBGs located at central office (CO) were fabricated and used as channel-by-channel dispersion compensators in order to mitigate the dispersion-induced distortion of both downstream and upstream signals. Owing to a low insertion loss of chirped FBG based dispersion compensator, the optical signal-to-noise ratio (OSNR) of the downstream signal could be improved to be ~28 dB. Thus, we re-confirmed that an error-free transmission of 1.25 Gb/s signals over a 100 km single-mode fiber (SMF) link could be achieved with a proposed amplified WDM-PON architecture. We have also evaluated the impact of various noises on the system's performance, and found that the low OSNR of the downstream signal would be a main limiting factor on the maximum reach of the proposed amplified WDM-PON architecture. From the measured ~13 dB improvement in OSNR of the downstream signal compared to our previously-proposed dispersion compensating module based scheme, we believe that the proposed architecture can accommodate a reach of longer than 100 km SMF link easily.
Optimizing the Net Gain of a Raman-EDFA Hybrid Optical Amplifier using a Genetic Algorithm
Singh, Simranjit ; Kaler, Rajinder Singh ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 442~448
DOI : 10.3807/JOSK.2014.18.5.442
For the first time, a novel analytical model of the net gain for a Raman-EDFA hybrid optical amplifier (HOA) is proposed and its various parameters optimized using a genetic algorithm. Our method has been shown to be robust in the simultaneous analysis of multiple parameters (Raman length, EDFA length, and pump powers) to obtain large gain. The optimized HOA is further investigated at the system level for the scenario of a 50-channel DWDM system with 0.2-nm channel spacing. With an optimized HOA, a flat gain of >17 dB is obtained over the effective ITU-T wavelength grid with a variation of less than 1.5 dB, without using any gain-flattening technique. The obtained noise figure is also the lowest value ever reported for a Raman-EDFA HOA at reduced channel spacing.
Sidelobe Suppression Enhancement of Radiofrequency Photonic Filters via Time-to-frequency Mapping
Song, Min-Hyup ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 449~452
DOI : 10.3807/JOSK.2014.18.5.449
We present a multi-tap microwave photonic filter with high selectivity through applying time-to-frequency mapping and optical frequency comb shaping techniques. When arranged in the time-to-frequency mapping stage, by a Fourier transform, the deviation of the optical taps to the target profile is significantly reduced while maintaining the apodization profile, resulting in high sidelobe suppression in the filters. By applying a simple time-to-frequency mapping stage to the conventional optical frequency combs, we demonstrate a substantially enhanced (>10dB) sidelobe suppression, resulting in filter lineshapes exhibiting a significantly high (>40dB) main lobe to sidelobe suppression ratio. These results highlight the potential of the technique for implementation in various passband filters with high sidelobe suppression.
A High Birefringent Polymer Terahertz Waveguide: Suspended Elliptical Core Fiber
Wang, Jingli ; Chen, Heming ; Shi, Weihua ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 453~458
DOI : 10.3807/JOSK.2014.18.5.453
A novel high birefringent polymer terahertz (THz) fiber with a suspended elliptical core is proposed in this paper. The introduction of an elliptical core can enhance asymmetry to realize high mode birefringence, and a large porous outer cladding effectively isolates the core-guided mode from interacting with the surrounding environment. A full-vector finite element method(FEM) is used to analyze the characteristics of the THz fiber. Simulation results show that the suspended elliptical fiber exhibits high mode birefringence on a level of
over a wide frequency range, and an extremely large mode birefringence(
) is obtained when ellipticity is 0.2. Moreover, a suspended hollow elliptical core fiber is also discussed for the purpose of lower loss, however high mode birefringence and low relative absorption loss can not coexist in such a kind of fiber.
Optimal Signal Amplitude of Orthogonal Frequency-Division Multiplexing Systems in Dimmable Visible Light Communications
Yun, Kyungsu ; Lee, Changho ; Ahn, Kang-Il ; Lee, Rimhwan ; Jang, Ja-Soon ; Kwon, Jae Kyun ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 459~465
DOI : 10.3807/JOSK.2014.18.5.459
Visible light communications (VLC) using the intensity modulation of light-emitting diodes (LEDs) provides a new communication medium to overcome the shortage of radio spectrum, and allows reuse of LED lighting infrastructures. Orthogonal frequency-division multiplexing (OFDM) was introduced to VLC for its merits in mitigating the fading effects resulting from delay spread, and in avoiding low-frequency ambient interference. Noise and clipping are two major factors that degrade the performance of OFDM in VLC. A larger signal easily overcomes noise, but experiences impairment by clipping. Therefore, degradation due to clipping has a trade-off relationship with that due to noise, depending on the signal amplitude of OFDM. In this paper, the optimal signal amplitude in the trade-off is obtained by simulation when the dimming and LED intensity are given. The former indicates a user's requirement for lighting, and the latter represents the channel quality. The required LED intensity-to-noise ratio, as the channel quality that guarantees dimming as well as an adequate bit-error rate (BER), is also discussed.
Dynamic Load-Balancing Algorithm Incorporating Flow Distributions and Service Levels for an AOPS Node
Zhang, Fuding ; Zhou, Xu ; Sun, Xiaohan ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 466~471
DOI : 10.3807/JOSK.2014.18.5.466
An asynchronous optical packet-switching (AOPS) node with load-balancing capability can achieve better performance in reducing the high packet-loss ratio (PLR) and time delay caused by unbalanced traffic. This paper proposes a novel dynamic load-balancing algorithm for an AOPS node with limited buffer and without wavelength converters, and considering the data flow distribution and service levels. By calculating the occupancy state of the output ports, load state of the input ports, and priorities for data flow, the traffic is balanced accordingly. Simulations demonstrate that asynchronous variant data packets and output traffic can be automatically balanced according to service levels and the data flow distribution. A PLR of less than 0.01% can be achieved, as well as an average time delay of less than 0.46 ns.
Image Blurring Estimation and Calibration with a Joint Transform Correlator
Jeong, Man Ho ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 472~476
DOI : 10.3807/JOSK.2014.18.5.472
The Joint Transform Correlator (JTC) has been the most suitable technique for real time optical pattern recognition and target tracking applications. This paper proposes a new application of the JTC system for an analysis of the blurring effect of the optical images caused by a defocused lens. We present the relation between the correlation peak, optical transfer function (OTF), and the amount of blurring caused by focusing error. Moreover, we show a possibility of calibrating the blurred image by simply measuring the correlation peak.
Optical Secret Key Sharing Method Based on Diffie-Hellman Key Exchange Algorithm
Jeon, Seok Hee ; Gil, Sang Keun ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 477~484
DOI : 10.3807/JOSK.2014.18.5.477
In this paper, we propose a new optical secret key sharing method based on the Diffie-Hellman key exchange protocol required in cipher system. The proposed method is optically implemented by using a free-space interconnected optical logic gate technique in order to process XOR logic operations in parallel. Also, we present a compact type of optical module which can perform the modified Diffie-Hellman key exchange for a cryptographic system. Schematically, the proposed optical configuration has an advantage of producing an open public key and a shared secret key simultaneously. Another advantage is that our proposed key exchange system uses a similarity to double key encryption techniques to enhance security strength. This can provide a higher security cryptosystem than the conventional Diffie-Hellman key exchange protocol due to the complexity of the shared secret key. Results of numerical simulation are presented to verify the proposed method and show the effectiveness in the modified Diffie-Hellman key exchange system.
Defocus Study of a Novel Optical Antenna Illuminated by a Radial Radiation Fiber Laser
Jiang, Ping ; Yang, Huajun ; Xie, Kang ; Yu, Mingyin ; Mao, Shengqian ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 485~494
DOI : 10.3807/JOSK.2014.18.5.485
A novel antenna with ellipsoid-paraboloid surfaces configuration is designed for matching the incident radial radiation fiber laser distribution for maximum transmission efficiency. The on-axial and off-axial defocus effects on the optical antenna system, resulting in energy loss, are analyzed in detail. Knowledge of the effects of those defocuses on beam divergence, aberration and antenna transmission efficiency is of great importance to the long range communication systems.
Determining Two-Sided Surface Profiles of Micro-Optical Elements Using a Dual-Wavelength Digital Holographic Microscope With Liquids
Lee, Hong Seok ; Shin, Sanghoon ; Lee, Heonjoo ; Yu, Younghun ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 495~499
DOI : 10.3807/JOSK.2014.18.5.495
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.
3-D Reconstruction of Human Face Using the Derivative Moiré Topography
Bae, Yoon Jae ; Ha, Byeong Wan ; Park, Ji An ; Cho, Choon Sik ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 500~506
DOI : 10.3807/JOSK.2014.18.5.500
A new 3-D reconstruction algorithm for the human face is proposed using the derivative Moir
topography which ensures fast and robust reconstruction even for rough surfaces. The Moir
interference fringe pattern is initially obtained through the projection Moir
topography based on phase shifting, and then differentiated to provide a full unwrapped phase map for a human face.
ambiguity, which has been a chronically unsolved problem with Moir
topography, is successfully surmounted by differentiating the Moir
fringe patterns both in x- and y-directions when the object is located in the x-y plane. A real human face is used for verifying the proposed derivative Moir
topography. A human face of 4 different phase-shifted images taken in the fixed plane is almost fully reconstructed in 3-D format in 0.1 mm lateral resolution.
Spectral Reflectivity Recovery from Tristimulus Values Using 3D Extrapolation with 3D Interpolation
Kim, Bog G. ; Werner, John S. ; Siminovitch, Michael ; Papamichael, Kostantinos ; Han, Jeongwon ; Park, Soobeen ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 507~516
DOI : 10.3807/JOSK.2014.18.5.507
We present a hybrid method for spectral reflectivity recovery, using 3D extrapolation as a supplemental method for 3D interpolation. The proposed 3D extrapolation is an extended version of 3D interpolation based on the barycentric algorithm. It is faster and more accurate than the conventional spectral-recovery techniques of principal-component analysis and nonnegative matrix transformation. Four different extrapolation techniques (based on nearest neighbors, circumcenters, in-centers, and centroids) are formulated and applied to recover spectral reflectivity. Under the standard conditions of a D65 illuminant and 1964
observer, all reflectivity data from 1269 Munsell color chips are successfully reconstructed. The superiority of the proposed method is demonstrated using statistical data to compare coefficients of correlation and determination. The proposed hybrid method can be applied for fast and accurate spectral reflectivity recovery in image processing.
3D Visualization of Partially Occluded Objects Using Axially Distributed Image Sensing With a Wide-Angle Lens
Kim, Nam-Woo ; Hong, Seok-Min ; Lee, Hoon Jae ; Lee, Byung-Gook ; Lee, Joon-Jae ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 517~522
DOI : 10.3807/JOSK.2014.18.5.517
In this paper we propose an axially distributed image-sensing method with a wide-angle lens to capture the wide-area scene of 3D objects. A lot of parallax information can be collected by translating the wide-angle camera along the optical axis. The recorded wide-area elemental images are calibrated using compensation of radial distortion. With these images we generate volumetric slice images using a computational reconstruction algorithm based on ray back-projection. To show the feasibility of the proposed method, we performed optical experiments for visualization of a partially occluded 3D object.
Study on the Improvement of the Image Analysis Speed in the Digital Image Correlation Measurement System for the 3-Point Bend Test
Choi, In Young ; Kang, Young June ; Hong, Kyung Min ; Kim, Seong Jong ; Lee, Gil Dong ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 523~530
DOI : 10.3807/JOSK.2014.18.5.523
Machine material and structural strain are critical factors for appraising mechanical properties and safety. Particularly in three and four-point bending tests, which appraise the deflection and flexural strain of an object due to external force, measurements are made by the crosshead movement or deflection meter of a universal testing machine. The Digital Image Correlation (DIC) method is one of the non-contact measurement methods. It uses the image analyzing method that compares the reference image with the deformed image for measuring the displacement and strain of the objects caused by external force. Accordingly, the advantage of this method is that the object's surface roughness, shape, and temperature have little influence. However, its disadvantage is that it requires extensive time to compare the reference image with the deformed image for measuring the displacement and strain. In this study, an algorithm is developed for DIC that can improve the speed of image analysis for measuring the deflection and strain of an object caused by a three-point bending load. To implement this algorithm for improving the speed of image analysis, LabVIEW 2010 was used. Furthermore, to evaluate the accuracy of the developed fast correlation algorithm, the deflection of an aluminum specimen under a three-point bending load was measured by using the universal test machine and DIC measurement system.
Methods to Measure the Critical Dimension of the Bottoms of Through-Silicon Vias Using White-Light Scanning Interferometry
Hyun, Changhong ; Kim, Seongryong ; Pahk, Heuijae ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 531~537
DOI : 10.3807/JOSK.2014.18.5.531
Through-silicon vias (TSVs) are fine, deep holes fabricated for connecting vertically stacked wafers during three-dimensional packaging of semiconductors. Measurement of the TSV geometry is very important because TSVs that are not manufactured as designed can cause many problems, and measuring the critical dimension (CD) of TSVs becomes more and more important, along with depth measurement. Applying white-light scanning interferometry to TSV measurement, especially the bottom CD measurement, is difficult due to the attenuation of light around the edge of the bottom of the hole when using a low numerical aperture. In this paper we propose and demonstrate four bottom CD measurement methods for TSVs: the cross section method, profile analysis method, tomographic image analysis method, and the two-dimensional Gaussian fitting method. To verify and demonstrate these methods, a practical TSV sample with a high aspect ratio of 11.2 is prepared and tested. The results from the proposed measurement methods using white-light scanning interferometry are compared to results from scanning electron microscope (SEM) measurements. The accuracy is highest for the cross section method, with an error of 3.5%, while a relative repeatability of 3.2% is achieved by the two-dimensional Gaussian fitting method.
Simulation Study on the Minimization of Moiré Patterns Caused by Microlens Array Films for Backlight Applications
Joo, Byung-Yun ; Ko, Jae-Hyeon ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 538~545
DOI : 10.3807/JOSK.2014.18.5.538
Microlens array (MLA) films have been used as brightness-enhancement components in many illumination systems, such as a backlight, which should meet the industrial needs of low cost and high brightness performance. A hexagonally-arranged MLA (HA-MLA) was chosen due to its high filling factor, which was a prerequisite for achieving high brightness-enhancement capability. The moir
fringes produced in a film stack composed of two HA-MLA were investigated, under four different lens configurations, by optical simulation. It was found that randomizing the lens configuration, while keeping the filling factor high, was effective way to develop high-gain MLA films for backlight applications.
Measurement Reliability of Axial Length of the Human Eye by using Partial Coherence Interferometry
Kim, Jae-Hyung ; Moon, Tae Hwan ; Chae, Ju Byung ; Hyung, Sungmin ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 546~550
DOI : 10.3807/JOSK.2014.18.5.546
To investigate the minimum near-infrared ray intensity required (quantifiable threshold value) for consistent measurements of axial length (AL) using partial coherence interferometry (PCI), we attached two polarizing lenses (PL) to two types of PCI (IOLmaster, ALscan). The near-infrared ray intensity of PCI was modified by rotating the axis of one PL at intervals of 5 degrees. The right eye of each volunteer was measured three times and the AL and signal-to-noise ratio (SNR) was recorded five times for each measurement. Reduction of light intensity was theoretically estimated using Malus' Law. AL was measured consistently with both IOLmaster and ALscan until they reached 55 degrees (1.33 % of intensity) and 60 degrees (0.77%), respectively (P = 0.343, Log-rank test). In contrast, SNR decreased as light intensity decreased. In addition, to analyze media opacities that precluded measurement of AL, we retrospectively reviewed the medical records of patients unmeasurable by PCI (ALscan) from May to November 2013. Thirty-eight of 473 eyes (8.0%) could not be measured using ALscan due to media opacities, such as severe posterior subcapsular cataract (PSC, 11 eyes), hypermature cataract (9 eyes), and vitreous hemorrhage (18 eyes). The mean grades of vitreous haze and PSC were
, respectively. In conclusion, up to 0.77-1.33% of near-infrared rays decreased, and AL could be measured consistently.
Multimodal Nonlinear Optical Microscopy for Simultaneous 3-D Label-Free and Immunofluorescence Imaging of Biological Samples
Park, Joo Hyun ; Lee, Eun-Soo ; Lee, Jae Yong ; Lee, Eun Seong ; Lee, Tae Geol ; Kim, Se-Hwa ; Lee, Sang-Won ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 551~557
DOI : 10.3807/JOSK.2014.18.5.551
In this study, we demonstrated multimodal nonlinear optical (NLO) microscopy integrated simultaneously with two-photon excitation fluorescence (TPEF), second-harmonic generation (SHG), and coherent anti-Stokes Raman scattering (CARS) in order to obtain targeted cellular and label-free images in an immunofluorescence assay of the atherosclerotic aorta from apolipoprotein E-deficient mice. The multimodal NLO microscope used two laser systems: picosecond (ps) and femtosecond (fs) pulsed lasers. A pair of ps-pulsed lights served for CARS (817 nm and 1064 nm) and SHG (817 nm) images; light from the fs-pulsed laser with the center wavelength of 720 nm was incident into the sample to obtain autofluorescence and targeted molecular TPEF images for high efficiency of fluorescence intensity without cross-talk. For multicolor-targeted TPEF imaging, we stained smooth-muscle cells and macrophages with fluorescent dyes (Alexa Fluor 350 and Alexa Fluor 594) for an immunofluorescence assay. Each depth-sectioned image consisted of
pixels with a field of view of
, a lateral resolution of
, and an axial resolution of
. We obtained composite multicolor images with conventional label-free NLO images and targeted TPEF images in atherosclerotic-plaque samples. Multicolor 3-D imaging of atherosclerotic-plaque structural and functional composition will be helpful for understanding the pathogenesis of cardiovascular disease.
Two-Dimensional Correlation Analysis of Sum-Frequency Vibrational Spectra of Langmuir Monolayers
Lee, Jonggwan ; Sung, Woongmo ; Kim, Doseok ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 558~563
DOI : 10.3807/JOSK.2014.18.5.558
Sum-frequency generation spectra of a Langmuir monolayer on water surface at varying surface areas were studied with two-dimensional correlation analysis. Upon enlarging the area/molecule of the Langmuir monolayer, the sum-frequency spectra changed reflecting the conformation change of the alkyl chains of the molecules in the monolayer. These changes stood out more clearly by employing two-dimensional correlation analysis of the above sum-frequency spectra. Features not very pronounced in the original spectra such as closely-spaced spectral bands can also be easily distinguished in the two-dimensional correlation spectra.
25-Gb/s Optical Transmitter with Si Ring Modulator and CMOS Driver
Rhim, Jinsoo ; Lee, Jeong-Min ; Yu, Byung-Min ; Ban, Yoojin ; Cho, Seong-Ho ; Choi, Woo-Young ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 564~568
DOI : 10.3807/JOSK.2014.18.5.564
We present a 25-Gb/s optical transmitter composed of a Si ring modulator and CMOS driver circuit. The Si ring modulator is realized with 220-nm Si-on-insulator process and the driver circuit with 65-nm CMOS process. The modulator and the driver are hybrid-integrated on the printed circuit board with bonding wires. The driver is designed so that the parasitic bonding wire inductance provides enhanced driver bandwidth. The transmitter successfully demonstrates 25-Gb/s operation.
Fabrication of Viewing Angle Direction Brightness-Enhancement Optical Films using Surface Textured Silicon Wafers
Jang, Wongun ; Shim, Hamong ; Lee, Dong-Kil ; Park, Youngsik ; Shin, Seong-Seon ; Park, Jong-Rak ; Lee, Ki Ho ; Kim, Insun ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 569~573
DOI : 10.3807/JOSK.2014.18.5.569
We demonstrate a low-cost, superbly efficient way of etching for the nano-, and micro-sized pyramid patterns on (100)-oriented Si wafer surfaces for use as a patterned master. We show a way of producing functional optical films for the viewing angle direction brightness-enhancement of Lambertian LED (light emitting diode)/OLED (organic light emitting diode) planar lighting applications. An optimally formulated KOH (Potassium hydroxide) wet etching process enabled random-positioned, and random size-distributed (within a certain size range) pyramid patterns to be developed over the entire (100) silicon wafer substrates up to 8" and a simple replication process of master patterns onto the PC (poly-carbonate) and PMMA (poly-methyl methacrylate) films were performed. Haze ratio values were measured for several film samples exhibiting excellent values over 90% suitable for LED/OLED lighting purposes. Brightness was also improved by 13~14% toward the viewing angle direction. Computational simulations using LightTools
were also carried out and turned out to be in strong agreement with experimental data. Finally, we could check the feasibility of fabricating low-cost, large area, high performance optical films for commercialization.
Design and Analysis of a 10× Optical Zoom System for an LWIR Camera
Ok, Chang-Min ; Park, Sung-Chan ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 574~581
DOI : 10.3807/JOSK.2014.18.5.574
This paper presents the design and evaluation of the optical zoom system for an LWIR camera. The 12.8operating wavelength range of this system is from
. Through a paraxial design and optimization process, we have obtained the extended four-group inner-focus zoom system with focal lengths of 10 to 100 mm, which consists of the six lenses including four aspheric surfaces and two diffractive surfaces. The diffractive lenses were used to balance the higher-order aberrations, and its diffraction properties were evaluated by scalar diffraction theory. We have calculated the polychromatic integrated diffraction efficiency and the MTF drop generated by background noise. The f-number of the zoom system is F/1.4 at all positions. Fields of view are given by
at wide field and
at narrow field positions. In conclusion, this design procedure results in a
compact zoom lens system useful for an LWIR camera.
Numerical Study of Polarization-Dependent Emission Properties of Localized-Surface-Plasmon-Coupled Light Emitting Diodes with Ag/SiO
Moon, Seul-Ki ; Yang, Jin-Kyu ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 582~588
DOI : 10.3807/JOSK.2014.18.5.582
We study polarization-dependent spontaneous emission (SE) rate and light extraction efficiency (LEE) in localized-surface-plasmon (LSP)-coupled light emitting diodes (LEDs). The closely packed seven
core-shell (CS) nanoparticles (NPs) lie on top of the GaN surface for LSP coupling with a radiated dipole. According to the dipole direction, both the SE rate and the LEE are significantly modified by the LSP effect at the
CS NPs when the size of Ag, the thickness of
, and the position of the dipole source are varied. The enhancement of the SE rate is related to an induced dipole effect at the Ag, and the high LEE is caused by light scattering with an LSP mode at
CS NPs. We suggest the optimum position of the quantum well (QW) in blue InGaN/GaN LEDs with
CS NPs for practical application.
Design and Performance Analysis of a Multi Wavelength Terahertz Modulator Based on Triple-Lattice Photonic Crystals
Ji, Ke ; Chen, Heming ; Zhou, Wen ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 589~593
DOI : 10.3807/JOSK.2014.18.5.589
Terahertz (THz) communication has important applications in high-speed and ultra broadband wireless access networks. The THz modulator is one of the key devices in a THz communications system. Wavelength division multiplexing (WDM) can expand the capacity of THz communications systems, so research on multi wavelength THz modulators has significant value. By combining photonic-crystal and THz technology, a novel type of multi wavelength THz modulator based on a triple-lattice photonic crystal is proposed in this paper. Compared to a compound-lattice photonic crystal, a triple-lattice photonic crystal has a larger gap width of 0.196. Simulation results show that six beams of THz waves can be modulated simultaneously with high performance. This modulator's extinction ratio is as large as 34.25 dB, its insertion loss is as low as 0.147 dB, and its modulation rate is 2.35 GHz.
Voltage-Dependent Residual Phase Noise of a Photodiode Measurement Based on a Two-Tone Correlation Method
Zhu, Dezhao ; Yang, Chun ; Cao, Zhewei ; Li, Xianghua ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 594~597
DOI : 10.3807/JOSK.2014.18.5.594
We propose a novel approach to measure the residual phase noise (RPN) of a photodiode (PD) based on a two-tone correlation method. Compared with the previous measurements of the RPNs of PDs, this method is more convenient in practical application. In this method, two microwave sources and other components were placed in two isolated links sharing the same PD, so the noises of them were uncorrelated. With an FFT analyzer, the uncorrelated noises could be mostly suppressed while only the RPN of the PD was preserved. Voltage-dependent nonlinearities of PDs were studied previously. In this letter, we investigate the relationship between the RPN of the PD and the bias voltage on the PD. By changing the bias voltage, the difference of the RPN can be up to 10 dB.
Diffusion Coefficients of CdSe/CdS Quantum Rods in Water Measured Using Polarized Fluorescence Correlation Spectroscopy
Lee, Jaeran ; Pack, Chan-Gi ; Kim, Soo Yong ; Kim, Sok Won ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 598~604
DOI : 10.3807/JOSK.2014.18.5.598
A polarization fluorescence correlation spectroscopy system based on a confocal microscope was built to study the rotational and translational diffusion of CdSe/CdS quantum rods (Q-rods), with the same and different polarization states between the polarizer and the analyzer (i.e. the XXX and XYY states). The rotational diffusion amplitude showed the dependences on polarization of
in the XXX state and
in the XYY state, when the translational diffusion amplitude was 1. The diffusion coefficients of the Q-rods were found based on their translational and rotational diffusion times in the two polarization states, in solutions with viscosity ranging from 0.9 to 6.9 cP. The translational and rotational diffusion coefficients ranged from
Measurement of Cloud Velocity and Altitude Using Lidar's Range Detection and Digital Image Correlation
Park, Nak-Gyu ; Baik, Sung-Hoon ; Park, Seung-Kyu ; Kim, Dong-Lyul ; Kim, Duk-Hyeon ; Choi, In-Young ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 605~610
DOI : 10.3807/JOSK.2014.18.5.605
Clouds play an important role in climate change, in the prediction of local weather, and also in aviation safety when instrument assisted flying is unavailable. Presently, various ground-based instruments used for the measurements of the cloud base height or velocity. Lidar techniques are powerful and have many applications in climate studies, including the clouds' temperature measurement, the aerosol particle properties, etc. Otherwise, it is very circumscribed in cloud velocity measurements because there is no Doppler effect if the clouds move in the perpendicular direction to the laser beam path of Doppler lidar. In this paper, we present a method for the measurement of cloud velocity using lidar's range detection and DIC (Digital Image Correlation) system to overcome the disadvantage of Doppler lidar. The lidar system acquires the distance to the cloud, and the cloud images are tracked using the developed fast correlation algorithm of DIC. We acquired the velocities of clouds using the calculated distance and DIC algorithm. The measurement values had a linear distribution.
Repetition-Rate Multiplication of a 10-GHz Mode-Locked Laser via Coding the Spectral Intensity and Phase
Kim, Ik Hwan ; Cho, Il Hwan ; Hong, Sang Jeen ; Seo, Dong-Sun ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 611~615
DOI : 10.3807/JOSK.2014.18.5.611
We report high-speed pulse train generation from a relatively low-speed 10-GHz mode-locked laser by means of line-by-line spectral coding. To increase the pulse repetition rate multiplication (RRM) factor, we combine coding schemes for both spectral intensity and phase by placing a simple mask at the coder focal plane. The resulting RRM factor, determined by multiplying the RRM factors of the individual coding schemes, rises as high as 16. To verify the generated pulses, the optical spectra and autocorrelation traces are examined.
Iridescent Specular Structural Colors of Two-Dimensional Periodic Diffraction Gratings
Yoon, Kyungsik ; Choi, Sujin ; Paek, Jeongyeup ; Im, Dajeong ; Roh, Jinyoung ; Kwon, Jaebum ; Kim, Hwi ;
Journal of the Optical Society of Korea, volume 18, issue 5, 2014, Pages 616~622
DOI : 10.3807/JOSK.2014.18.5.616
Specular structural colors generated by two-dimensional periodic binary gratings are investigated theoretically. An approximate mathematical model of the grating specular structural colors is described, based on scalar nonparaxial diffraction theory, and the functional relationships of specular structural color and structural parameters of gratings are analyzed. Through this, the optimal condition for maximizing the color-representation range in the standard CIE 1931 chromaticity diagram is derived.