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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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Double Random Phase Encryption using Orthogonal Encoding for Multiple-Image Transmission
Lee, In-Ho ; Cho, Myungjin ;
Journal of the Optical Society of Korea, volume 18, issue 3, 2014, Pages 201~206
DOI : 10.3807/JOSK.2014.18.3.201
In this paper we extend double random phase encryption (DRPE) using orthogonal encoding from single-image transmission to multiple-image transmission. The orthogonal encoding for multiple images employs a larger Hadamard matrix than that for a single image, which can improve security. We provide a scheme for DRPE with an orthogonal codec, and a method for orthogonal encoding/decoding for multiple-image transmission. Finally, simulation results verify that the DRPE using orthogonal encoding for multiple images is more secure than both the conventional DRPE and the DRPE using orthogonal encoding for a single image.
Near-elliptic Core Triangular-lattice and Square-lattice PCFs: A Comparison of Birefringence, Cut-off and GVD Characteristics Towards Fiber Device Application
Maji, Partha Sona ; Chaudhuri, Partha Roy ;
Journal of the Optical Society of Korea, volume 18, issue 3, 2014, Pages 207~216
DOI : 10.3807/JOSK.2014.18.3.207
In this work, we report detailed numerical analysis of the near-elliptic core index-guiding triangular-lattice and square-lattice photonic crystal fiber (PCFs); where we numerically characterize the birefringence, single mode, cut-off behavior and group velocity dispersion and effective area properties. By varying geometry and examining the modal field profile we find that for the same relative values of
, triangular-lattice PCFs show higher birefringence whereas the square-lattice PCFs show a wider range of single-mode operation. Square-lattice PCF was found to be endlessly single-mode for higher air-filling fraction (
). Dispersion comparison between the two structures reveal that we need smaller lengths of triangular-lattice PCF for dispersion compensation whereas PCFs with square-lattice with nearer relative dispersion slope (RDS) can better compensate the broadband dispersion. Square-lattice PCFs show zero dispersion wavelength (ZDW) red-shifted, making it preferable for mid-IR supercontinuum generation (SCG) with highly non-linear chalcogenide material. Square-lattice PCFs show higher dispersion slope that leads to compression of the broadband, thus accumulating more power in the pulse. On the other hand, triangular-lattice PCF with flat dispersion profile can generate broader SCG. Square-lattice PCF with low Group Velocity Dispersion (GVD) at the anomalous dispersion corresponds to higher dispersion length (
) and higher degree of solitonic interaction. The effective area of square-lattice PCF is always greater than its triangular-lattice counterpart making it better suited for high power applications. We have also performed a comparison of the dispersion properties of between the symmetric-core and asymmetric-core triangular-lattice PCF. While we need smaller length of symmetric-core PCF for dispersion compensation, broadband dispersion compensation can be performed with asymmetric-core PCF. Mid-Infrared (IR) SCG can be better performed with asymmetric core PCF with compressed and high power pulse, while wider range of SCG can be performed with symmetric core PCF. Thus, this study will be extremely useful for designing/realizing fiber towards a custom application around these characteristics.
Fast-Converging Algorithm for Wavefront Reconstruction based on a Sequence of Diffracted Intensity Images
Chen, Ni ; Yeom, Jiwoon ; Hong, Keehoon ; Li, Gang ; Lee, Byoungho ;
Journal of the Optical Society of Korea, volume 18, issue 3, 2014, Pages 217~224
DOI : 10.3807/JOSK.2014.18.3.217
A major advantage of wavefront reconstruction based on a series of diffracted intensity images using only single-beam illumination is the simplicity of setup. Here we propose a fast-converging algorithm for wavefront calculation using single-beam illumination. The captured intensity images are resampled to a series of intensity images, ranging from highest to lowest resampling; each resampled image has half the number of pixels as the previous one. Phase calculation at a lower resolution is used as the initial solution phase at a higher resolution. This corresponds to separately calculating the phase for the lower- and higher-frequency components. Iterations on the low-frequency components do not need to be performed on the higher-frequency components, thus making the convergence of the phase retrieval faster than with the conventional method. The principle is verified by both simulation and optical experiments.
Reflection-type Three-dimensional Screen using Retroreflector
Song, Byoungsub ; Choi, Sungwon ; Sung, Hyunsik ; Min, Sung-Wook ;
Journal of the Optical Society of Korea, volume 18, issue 3, 2014, Pages 225~229
DOI : 10.3807/JOSK.2014.18.3.225
A reflection-type three-dimensional (3D) screen using retroreflector is proposed to improve the visibility of a projected 3D image while keeping its perspective. For the projection-type 2D display, the diffuser is used to represent the 2D scene, overcoming the limitation of the aperture of the projection lens set. If the diffuser is adopted for the projected 3D image, only 2D images sectioned and blurred should be displayed on the screen. The proposed screen can make the 3D image with the aperture limitation visible to be applied to the 3D image projection systems. The feasibility of the proposed screen is verified by experiments.
Experimental Study of Two-step Phase-shifting Digital Holography based on the Calculated Intensity of a Reference Wave
Li, Jun ; Pan, Yang Yang ; Li, Jiao sheng ; Li, Rong ; Zheng, Tao ;
Journal of the Optical Society of Korea, volume 18, issue 3, 2014, Pages 230~235
DOI : 10.3807/JOSK.2014.18.3.230
Two-step quadrature phase-shifting digital holography based on the calculated intensity of a reference wave is proposed. In the Mach-Zehnder interferometer (MZI) architecture, the method only records two quadrature-phase holograms, without reference-wave intensity or object-wave intensity measurement, to perform object recoding and reconstruction. When the reference-wave intensity is calculated from the 2D correlation coefficient (CC) method that we presented, the clear reconstruction image can be obtained by some specific algorithm. Its feasibility and validity were verified by a series of experiments with 2D objects and 3D objects. The presented method will be widely used in real-time or dynamic digital holography applications.
Thickness and Surface Measurement of Transparent Thin-Film Layers using White Light Scanning Interferometry Combined with Reflectometry
Jo, Taeyong ; Kim, KwangRak ; Kim, SeongRyong ; Pahk, HeuiJae ;
Journal of the Optical Society of Korea, volume 18, issue 3, 2014, Pages 236~243
DOI : 10.3807/JOSK.2014.18.3.236
Surface profiling and film thickness measurement play an important role for inspection. White light interferometry is widely used for engineering surfaces profiling, but its applications are limited primarily to opaque surfaces with relatively simple optical reflection behavior. The conventional bucket algorithm had given inaccurate surface profiles because of the phase error that occurs when a thin-film exists on the top of the surface. Recently, reflectometry and white light scanning interferometry were combined to measure the film thickness and surface profile. These techniques, however, have found that many local minima exist, so it is necessary to make proper initial guesses to reach the global minimum quickly. In this paper we propose combing reflectometry and white light scanning interferometry to measure the thin-film thickness and surface profile. The key idea is to divide the measurement into two states; reflectometry mode and interferometry mode to obtain the thickness and profile separately. Interferogram modeling, which considers transparent thin-film, was proposed to determine parameters such as height and thickness. With the proposed method, the ambiguity in determining the thickness and the surface has been eliminated. Standard thickness specimens were measured using the proposed method. Multi-layered film measurement results were compared with AFM measurement results. The comparison showed that surface profile and thin-film thickness can be measured successfully through the proposed method.
Out-of-Band Measurement of LED-based Solar Blind UV Filters
Cui, Muhan ; Zhou, Yue ; Chen, Xue ; Yan, Feng ; Zhang, Mingchao ; Yang, Huaijiang ;
Journal of the Optical Society of Korea, volume 18, issue 3, 2014, Pages 244~250
DOI : 10.3807/JOSK.2014.18.3.244
Due to the difficulty in measuring very low out-of-band cutoff depths of solar blind UV filters, we propose a cutoff depth adjustable measurement system (CDAM) to test deep cutoff filters with a large dynamic range. The CDAM utilizing the substitution method is elaborately composed of several parts, including narrow-band LED light sources, standard reflective neutral attenuators with known attenuation coefficients, and a photomultiplier (PMT). This paper also presents an attenuator combination method ensuring that the PMT works within its linear response range. In addition, numerical simulation testifies to the method, and experiment shows that the CDAM system can achieve an extension of dynamic range from 0-6 OD to 0-10 OD, which is sufficient for the measurement of out-of-band cutoff depths of solar blind UV filters. Above all, the CDAM system, being easily implemented, of wide dynamic range, and highly precise, could be widely used in the measurement of filter cutoff depth.
Fiber-based Diffuser Sheet for Liquid Crystal Display Backlight Unit
Kim, Taehyung ; Lee, Eun Soo ; Jeong, Won Young ; Lim, Dae Young ; Choi, Suk-Won ;
Journal of the Optical Society of Korea, volume 18, issue 3, 2014, Pages 251~255
DOI : 10.3807/JOSK.2014.18.3.251
A fiber diffuser sheet based on poly (ethylene naphthalate) (PEN) and poly (methylpentene) (PMP) has shown potential for liquid crystal display backlight units, but these materials have an interfacial adhesion problem. To improve the interfacial adhesion between the fibers and matrix components, we have proposed the use of amorphous poly (cyclohexane-1,4-dimethylene terephthalate) (Tritan) instead of PEN. Furthermore, the fabrication processes have been optimized and simplified to improve the optical and mechanical properties of the sheet. As a result, the most effective fiber content for achieving the best haze characteristics of a sample consisting of Tritan and PMP has been identified.
-Coated Reflective Layer Enhances the Sensitivity of a CsI:Tl Scintillator for X-ray Imaging Sensors
Kim, Youngju ; Kim, Byoungwook ; Kwon, Youngman ; Kim, Jongyul ; Kim, MyungSoo ; Cho, Gyuseong ; Jun, Hong Young ; Thap, Tharoeun ; Lee, Jinseok ; Yoon, Kwon-Ha ;
Journal of the Optical Society of Korea, volume 18, issue 3, 2014, Pages 256~260
DOI : 10.3807/JOSK.2014.18.3.256
Columnar-structured cesium iodide (CsI) scintillators doped with thallium (Tl) are frequently used as x-ray converters in medical and industrial imaging. In this study we investigated the imaging characteristics of CsI:Tl films with various reflective layers-aluminum (Al), chromium (Cr), and titanium dioxide (
) powder-coated on glass substrates. We used two effusion-cell sources in a thermal evaporator system to fabricate CsI:Tl films on substrates. The scintillators were observed via scanning electron microscopy (SEM), and scintillation characteristics were evaluated on the basis of the emission spectrum, light output, light response to x-ray dose, modulation transfer function (MTF), and x-ray images. Compared to control films without a reflective layer, CsI:Tl films with reflective layers showed better sensitivity and light collection efficiency, and the film with a
reflective layer showed the best properties.
Improved Plasmonic Filter, Ultra-Compact Demultiplexer, and Splitter
Rahimzadegan, Aso ; Granpayeh, Nosrat ; Hosseini, Seyyed Poorya ;
Journal of the Optical Society of Korea, volume 18, issue 3, 2014, Pages 261~273
DOI : 10.3807/JOSK.2014.18.3.261
In this paper, metal insulator metal (MIM) plasmonic slot cavity narrow band-pass filters (NBPFs) are studied. The metal and dielectric of the structures are silver (Ag) and air, respectively. To improve the quality factor and attenuation range, two novel NBPFs based on tapered structures and double cavity systems are proposed and numerically analyzed by using the two-dimensional (2-D) finite difference time domain (FDTD) method. The impact of different parameters on the transmission spectrum is scrutinized. We have shown that increasing the cavities' lengths increases the resonance wavelength in a linear relationship, and also increases the quality factor, and simultaneously the attenuation of the wave transmitted through the cavities. Furthermore, increasing the slope of tapers of the input and output waveguides decreases attenuation of the wave transmitted through the waveguide, but simultaneously decreases the quality factor, hence there should be a trade-off between loss and quality factor. However, the idea of adding tapers to the waveguides' discontinuities of the simple structure helps us to improve the device total performance, such as quality factor for the single cavity and attenuation range for the double cavity. According to the proposed NBPFs, two, three, and four-port power splitters functioning at 1320 nm and novel ultra-compact two-wavelength and triple-wavelength demultiplexers in the range of 1300-1550 nm are proposed and the impacts of different parameters on their performances are numerically investigated. The idea of using tapered waveguides at the structure discontinuities facilitates the design of ultra-compact demultiplexers and splitters.
Gold Shell Nanocluster Networks in Designing Four-Branch (1×4) Y-Shape Optical Power Splitters
Ahmadivand, Arash ; Golmohammadi, Saeed ;
Journal of the Optical Society of Korea, volume 18, issue 3, 2014, Pages 274~282
DOI : 10.3807/JOSK.2014.18.3.274
In this study, closely spaced Au nanoparticles which are arranged in nanocluster (heptamer) configurations have been employed to design efficient plasmonic subwavelength devices to function at the telecommunication spectrum (
~1550 nm). Utilizing two kinds of nanoparticles, the optical properties of heptamer clusters composed of Au rod and shell particles that are oriented in triphenylene molecular fashion have been investigated numerically, and the cross-sectional profiles of the scattering and absorption of the optical power have been calculated based on a finite-difference time-domain (FDTD) method. Plasmon hybridization theory has been utilized as a theoretical approach to characterize the features and properties of the adjacent and mutual heptamer clusters. Using these given nanostructures, we designed a complex four-branch (
) Y-shape splitter that is able to work at the near infrared region (NIR). This splitter divides and transmits the magnetic plasmon mode along the mutual heptamers arrays. Besides, as an important and crucial parameter, we studied the impact of arm spacing (offset distance) on the guiding and dividing of the magnetic plasmon resonance propagation and by calculating the ratio of transported power in both nanorod and nanoshell-based structures. Finally, we have presented the optimal structure, that is the four-branch Y-splitter based on shell heptamers which yields the power ratio of 23.9% at each branch, 4.4
decaying length, and 1450 nm offset distance. These results pave the way toward the use of nanoparticles clusters in molecular fashions in designing various efficient devices that are able to be efficient at NIR.
Enhanced Cathodoluminescence of KOH-treated InGaN/GaN LEDs with Deep Nano-Hole Arrays
Doan, Manh-Ha ; Lee, Jaejin ;
Journal of the Optical Society of Korea, volume 18, issue 3, 2014, Pages 283~287
DOI : 10.3807/JOSK.2014.18.3.283
Square lattice nano-hole arrays with diameters and periodicities of 200 and 500 nm, respectively, are fabricated on InGaN/GaN blue light emitting diodes (LEDs) using electron-beam lithography and inductively coupled plasma reactive ion etching processes. Cathodoluminescence (CL) investigations show that light emission intensity from the LEDs with the nano-hole arrays is enhanced compared to that from the planar sample. The CL intensity enhancement factor decreases when the nano-holes penetrate into the multiple quantum wells (MQWs) due to the plasma-induced damage and the residues. Wet chemical treatment using KOH solution is found to be an effective method for light extraction from the nano-patterned LEDs, especially, when the nano-holes penetrate into the MQWs. About 4-fold CL intensity enhancement factor is achieved by the KOH treatments after the dry etching for the sample with a 250-nm deep nano-hole array.
A Novel Measurement Approach for the Half-wave Voltage of Phase Modulator based on PM-MZI Photonic Link
Xianghua, Li ; Chun, Yang ; Quanyi, Ye ; Yuhua, Chong ; Zhenghua, Zhou ;
Journal of the Optical Society of Korea, volume 18, issue 3, 2014, Pages 288~291
DOI : 10.3807/JOSK.2014.18.3.288
This paper presents a new method for measuring the half-wave voltage
of an electro-optic phase modulator based on a phase-modulated photonic link with interferometric demodulation. By using this method, the
can be obtained with the RF voltage amplitude input required to achieve 1-dB gain compression of link and the differential delay of a Mach-Zehnder interferometer. We measure the
of a commercial phase modulator by using the presented method and the carrier/the first sideband intensity ratio method. Furthermore, we compare the two measurements with the typical value provided by the manufacturer. The experiment shows that this novel measurement method is feasible, straightforward, and accurate.
Erratum : General Theory of Wave Scattering by Two Separated Particles
Park, Byong Chon ; Kim, Myung-Whun ; Kim, Jin Seung ;
Journal of the Optical Society of Korea, volume 18, issue 3, 2014, Pages 292~292
DOI : 10.3807/JOSK.2014.18.3.292