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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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The Effects of Various Apodization Functions on the Filtering Characteristics of the Grating-Assisted SOI Strip Waveguides
Karimi, Azadeh ; Emami, Farzin ; Nozhat, Najmeh ;
Journal of the Optical Society of Korea, volume 18, issue 2, 2014, Pages 101~109
DOI : 10.3807/JOSK.2014.18.2.101
In this paper, four apodization functions are proposed for silicon-on-insulator (SOI) strip waveguides with sidewall-corrugated gratings. The effects of apodization functions on the full width at half maximum (FWHM), the side-lobe level, and the reflectivity of the reflection spectrum are studied using the coupled-mode theory (CMT) and the transfer-matrix method (TMM). The results show that applying proposed apodization functions creates very good filtering characteristics. Among investigated apodized waveguides, the apodization functions of Polynomial and z-power have the best performance in reducing side-lobes, where the side-lobe oscillations are entirely removed. Four functions are also used for precise adjustment of the bandwidth. Simulation results show that the minimum and maximum values of the FWHM are 0.74 nm and 8.48 nm respectively. In some investigated functions, changing the apodization parameters decreases the reflectivity which is compensated by increasing the grating length.
Double-Pass System (Optical Quality Analysis System) for Analysis of the Multifocal Function of a Diffractive Multifocal Intraocular Lens (Acrysof ReSTOR®) Compared to a Monofocal Intraocular Lens (Acrysof IQ®)
Hwang, Ho Sik ; Shin, Hye Young ; Joo, Choun-Ki ;
Journal of the Optical Society of Korea, volume 18, issue 2, 2014, Pages 110~117
DOI : 10.3807/JOSK.2014.18.2.110
In this study, we objectively determined whether the ReSTOR as a multifocal IOL (intraocular lens) has a multifocal function compared to the IQ as a monofocal IOL in vivo by OQAS (Optical Quality Analysis System). Eighteen patients who had cataract surgery with implantation of ReSTOR (27 eyes) and 15 patients with IQ (21 eyes), were included inthis study. Uncorrected distance visual acuity (UCDVA), corrected distance visual acuity (CDVA), uncorrected near visual acuity (UCNVA)and distance corrected near visual acuity (DCNVA) were measured. After setting the artificial pupil size to 3 mm, we performed 'Optical quality'. We inputted defocus diopters of (objective spherical refraction)(far), (objective spherical refraction-1.25 D)(intermediate),(objective spherical refraction-2.5 D)(near), and (objective spherical refraction-3.5 D)(very near) into 'selected spherical refraction' simulating the optical quality at far, intermediate, and near distance. We changed the pupil size to 5 mm and repeated the same measurements. The UCDVA and CDVA did not show significant differences between the 2 groups. But, the UCNVA and DCNVA of the ReSTOR group were better than those of the IQ group (p=0.000, p=0.000). For 3 mm pupil, at far distance, modulation transfer function (MTF) cut off and point spread function (PSF) width at 50% of ReSTOR were worse than those of IQ (p=0.039, p=0.020). At intermediate distance, MTF cut off, Strehl ratio and PSF width at 50% of ReSTOR were worse than those of IQ (p=0.001, p=0.001, p=0.000). At near distance, MTF cut off of ReSTOR was worse than that of IQ (p=0.033). At very near distance, MTF cut off and Strehl ratio of ReSTOR were worse than those of IQ (p=0.002, p=0.002), but PSF width at 50% of ReSTOR was better than that of IQ. For 5 mm pupil, most parameters at each distance, there was no significant difference between the 2 groups. Only PSF width at 50% of ReSTOR were worse than those of IQ at intermediate distance (p=0.013). It was impossible to show the multifocal function of ReSTOR compared to the IQ byOQAS.
On the Optimization of Raman Fiber Amplifier using Genetic Algorithm in the Scenario of a 64 nm 320 Channels Dense Wavelength Division Multiplexed System
Singh, Simranjit ; Saini, Sonak ; Kaur, Gurpreet ; Kaler, Rajinder Singh ;
Journal of the Optical Society of Korea, volume 18, issue 2, 2014, Pages 118~123
DOI : 10.3807/JOSK.2014.18.2.118
For multi parameter optimization of Raman Fiber Amplifier (RFA), a simple genetic algorithm is presented in the scenario of a 320 channel Dense Wavelength Division Multiplexed (DWDM) system at channel spacing of 25 GHz. The large average gain (> 22 dB) is observed from optimized RFA with the optimized parameters, such as 39.6 km of Raman length with counter-propagating pumps tuned to 205.5 THz and 211.9 THz at pump powers of 234.3 mW, 677.1 mW respectively. The gain flattening filter (GFF) has also been optimized to further reduce the gain ripple across the frequency range from 190 to 197.975 THz for broadband amplification.
Joint Probability Density Functions for Direct-Detection Optical Receivers
Lee, Jae Seung ;
Journal of the Optical Society of Korea, volume 18, issue 2, 2014, Pages 124~128
DOI : 10.3807/JOSK.2014.18.2.124
We derive joint probability density functions (JPDFs) for two adjacent data from direct-detection optical receivers in dense wavelength-division multiplexing systems. We show that the decision using two data per bit can increase the receiver sensitivity compared with the conventional decision. Our JPDFs can be used for software-defined optical receivers enhancing the receiver sensitivities for intensity-modulated channels.
Double Random Phase Encryption Based Orthogonal Encoding Technique for Color Images
Lee, In-Ho ; Cho, Myungjin ;
Journal of the Optical Society of Korea, volume 18, issue 2, 2014, Pages 129~133
DOI : 10.3807/JOSK.2014.18.2.129
In this paper, we propose a simple Double random phase encryption (DRPE)-based orthogonal encoding technique for color image encryption. In the proposed orthogonal encoding technique, a color image is decomposed into red, green, and blue components before encryption, and the three components are independently encrypted with DRPE using the same key in order to decrease the complexity of encryption and decryption. Then, the encrypted data are encoded with a Hadamard matrix that has the orthogonal property. The purpose of the proposed orthogonal encoding technique is to improve the security of DRPE using the same key at the cost of a little complexity. The proposed orthogonal encoder consists of simple linear operations, so that it is easy to implement. We also provide the simulation results in order to show the effects of the proposed orthogonal encoding technique.
Unified Analytic Calculation Method for Zoom Loci of Zoom Lens Systems with a Finite Object Distance
Ryu, Jae Myung ; Oh, Jeong Hyo ; Jo, Jae Heung ;
Journal of the Optical Society of Korea, volume 18, issue 2, 2014, Pages 134~145
DOI : 10.3807/JOSK.2014.18.2.134
The number of lens groups in modern zoom camera systems is increased above that of conventional systems in order to improve the speed of the auto focus with the high quality image. As a result, it is difficult to calculate zoom loci using the conventional analytic method, and even the recent one-step advanced numerical calculation method is not optimal because of the time-consuming problem generated by the iteration method. In this paper, in order to solve this problem, we suggest a new unified analytic method for zoom lens loci with finite object distance including infinite object distance. This method is induced by systematically analyzing various distances between the object and other groups including the first lens group, for various situations corresponding to zooming equations of the finite lens systems after using a spline interpolation for each lens group. And we confirm the justification of the new method by using various zoom lens examples. By using this method, we can easily and quickly obtain the zoom lens loci not only without any calculation process of iteration but also without any limit on the group number and the object distance in every zoom lens system.
Two-step Holographic Imaging Method based on Single-pixel Compressive Imaging
Li, Jun ; Li, Yaqing ; Wang, Yuping ; Li, Ke ; Li, Rong ; Li, Jiaosheng ; Pan, Yangyang ;
Journal of the Optical Society of Korea, volume 18, issue 2, 2014, Pages 146~150
DOI : 10.3807/JOSK.2014.18.2.146
We propose an experimental holographic imaging scheme combining compressive sensing (CS) theory with digital holography in phase-shifting conditions. We use the Mach-Zehnder interferometer for hologram formation, and apply the compressive sensing (CS) approach to the holography acquisition process. Through projecting the hologram pattern into a digital micro-mirror device (DMD), finally we will acquire the compressive sensing measurements using a photodiode. After receiving the data of two holograms via conventional communication channel, we reconstruct the original object using certain signal recovery algorithms of CS theory and hologram reconstruction techniques, which demonstrated the feasibility of the proposed method.
Array-Based Real-Time Ultrasound and Photoacoustic Ocular Imaging
Nam, Seung Yun ; Emelianov, Stanislav Y. ;
Journal of the Optical Society of Korea, volume 18, issue 2, 2014, Pages 151~155
DOI : 10.3807/JOSK.2014.18.2.151
Although various ophthalmic imaging methods, including fundus photography and optical coherence tomography, have been applied for effective diagnosis of ocular diseases with high spatial resolution, most of them are limited by shallow imaging penetration depth and a narrow field of view. Also, many of those imaging modalities are optimized to provide microscopic anatomical information, while functional or cellular information is lacking. Compared to other ocular imaging modalities, photoacoustic imaging can achieve relatively deep penetration depth and provide more detailed functional and cellular data based on photoacoustic signal generation from endogenous contrast agents such as hemoglobin and melanin. In this paper, array-based ultrasound and photoacoustic imaging was demonstrated to visualize pigmentation in the eye as well as overall ocular structure. Fresh porcine eyes were visualized using a real-time ultrasound micro-imaging system and an imaging probe supporting laser pulse delivery. In addition, limited photoacoustic imaging field of view was improved by an imaging probe tilting method, enabling visualization of most regions of the retina covered in the ultrasound imaging.
Study of Ultra-Small Optical Anisotropy Profile of Rubbed Polyimide Film by using Transmission Ellipsometry
Lyum, Kyung Hun ; Yoon, Hee Kyu ; Kim, Sang Jun ; An, Sung Hyuck ; Kim, Sang Youl ;
Journal of the Optical Society of Korea, volume 18, issue 2, 2014, Pages 156~161
DOI : 10.3807/JOSK.2014.18.2.156
Anisotropy profile of a rubbed polyimide film is investigated using both a modified ultra high precision transmission ellipsometer and the analysis software previously developed to determine the optic axis distribution of discotic liquid crystals in the wide view film. The distorted sinusoidal variation of the ellipsometric constants obtained at an oblique angle of incidence indicates that the optic axis varies from
from the sample plane. The magnitude and distribution of anisotropy is expressed in terms of no, ne, and the cosine-shaped tilt angle distribution of the optic axis in a rubbed polyimide film.
Impact of Booster Section Length on the Performance of Linear Cavity Brillouin-Erbium Fiber Laser
Al-Mashhadani, Thamer Fahad ; Jamaludin, Md. Zaini ; Al-Mansoori, Mohammed Hayder ; Abdullah, Fairuz ; Abbas, Abdulla Khudair ;
Journal of the Optical Society of Korea, volume 18, issue 2, 2014, Pages 162~166
DOI : 10.3807/JOSK.2014.18.2.162
The impact of booster section length made from passive erbium-doped fiber (EDF) on the L-band multiwavelength Brillouin-Erbium fiber laser (MBEFL) is studied experimentally in this paper. The influence on the performance of MBEFL in term of number of generated Stokes lines, tuning range and lasing threshold were investigated. A comparison was made between MBEFL without a booster section and with booster sections of different lengths. Through comparative study and at fixed BP power and 100mW of 1480 pump power, longer passive EDF length of 5m exhibits the highest average number of Stokes lines of 23 with tuning range of 14nm. In contrast, shorter passive EDF length of 1m shows the highest tuning range of 17nm and an average number of 21 Stokes lines.
High Power Single Mode Multi-Oxide Layer VCSEL with Optimized Thicknesses and Aperture Sizes of Oxide Layers
Yazdanypoor, Mohammad ; Emami, Farzin ;
Journal of the Optical Society of Korea, volume 18, issue 2, 2014, Pages 167~173
DOI : 10.3807/JOSK.2014.18.2.167
A novel multi-oxide layer structure for vertical cavity surface emitting laser (VCSEL) structures is proposed to achieve higher single mode output power. The structure has four oxide layers with different aperture sizes and thicknesses. The oxide layer thicknesses are optimized simultaneously to reach the highest single mode output power. A heuristic method is proposed for plotting the influence of these variable changes on the operation of optical output power. A comprehensive optical-electrical thermal-gain self-consistent VCSEL model is used to simulate the continuous-wave operation of the multi-layer oxide VCSELs. A comparison between optimized VCSELs with different structures is presented. The results show that by using multi-oxide layers with different thicknesses, higher single-mode optical output power could be achieved in comparison with multi-oxide layer structures with the same thicknesses.
In Vitro Biocompatibility Test of Multi-layered Plasmonic Substrates with Flint Glasses and Adhesion Films
Kim, Nak-Hyeon ; Byun, Kyung Min ; Hwang, Seoyoung ; Lee, Yena ; Jun, Sang Beom ;
Journal of the Optical Society of Korea, volume 18, issue 2, 2014, Pages 174~179
DOI : 10.3807/JOSK.2014.18.2.174
Since in vitro neural recording and imaging applications based on a surface plasmon resonance (SPR) technique have expanded dramatically in recent years, cytotoxicity assessment to ensure the biosafety and biocompatibility for those applications is crucial. Here, we report the cytotoxicity of the SPR substrate incorporating a flint glass whose refractive index is larger than that of a conventional crown glass. A high refractive index glass substrate is essential in neural signal detection due to the advantages such as high sensitivity and wide dynamic range. From experimental data using primary hippocampal neurons, it is found that a lead-based flint glass is not appropriate as a neural recording template although the neuron cells are not directly attached to the toxic glass. We also demonstrate that the adhesion layer between the glass substrate and the gold film plays an important role in achieving the substrate stability and the cell viability.
Simulation of Rough Surface of CIGS (CuInGaSe) Solar Cell by RCWA (Rigorous Coupled Wave Analysis) Considering the Incoherency of Light
Kim, Sung Chul ;
Journal of the Optical Society of Korea, volume 18, issue 2, 2014, Pages 180~183
DOI : 10.3807/JOSK.2014.18.2.180
The surface of semiconductor solar cells, such as a-Si or CIGS (CuInGaSe) solar cells is not flat but textured in the microscopic domain. With textured surfaces, the optical reflectivity of a solar cell is different from that of flat surfaces in the wavelength region. In this paper, the effects of a textured surface on a CIGS solar cell are presented by RCWA (Rigorous Coupled Wave Analysis) method. The effect of incoherent light is also considered by RCWA with a Fourier analysis while conventional optical simulation uses the input light on the solar cell as coherent light. Using experimental results, the author showed that the RCWA method with a Fourier analysis is a proper method to simulate the optical properties of CIGS solar cells.
Size Effect of Light Scattering on the Nano-Sized Color Filter Pigment in Liquid Crystal Display
Jhun, Chul Gyu ; Gwag, Jin Seog ;
Journal of the Optical Society of Korea, volume 18, issue 2, 2014, Pages 184~187
DOI : 10.3807/JOSK.2014.18.2.184
This study examined the effects of particle size on the light scattering of a nano-sized color filter pigment used to obtain a range of colors in liquid crystal displays. The contrast ratio is one of the most important characteristics of liquid crystal displays. When a color filter is located between two crossed polarizers, the size of the pigment can give rise to a decrease in the contrast ratio due to Rayleigh scattering by the nanoparticles in the filter. The size effect of the color filter pigment on the contrast ratio was investigated in terms of the depolarization parameter. As an experimental result, the depolarization parameter increased with decreasing pigment size. Therefore, a smaller pigment size can reduce light leakage caused by light scattering in the color filter between two crossed polarizers. The depolarization function was also proposed as a useful function for predicting the decrease in the contrast ratio of the color filter.
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 2, 2014, Pages 188~193
DOI : 10.3807/JOSK.2014.18.2.188
A general theory of scalar wave scattering by two separated particles is developed to give the coefficients of scattering and transmission in the form of recurrence formulae. Iterative applications of the formulae yield the coefficients in the form of power series of the coefficients obtained from single-particle scattering theories, and each term of the of power series can be interpreted as multiple scattering of the wave between the two particles in increasingly higher order.