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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 14, Issue 6 - Dec 2003
Volume 14, Issue 5 - Oct 2003
Volume 14, Issue 4 - Aug 2003
Volume 14, Issue 3 - Jun 2003
Volume 14, Issue 2 - Apr 2003
Volume 14, Issue 1 - Feb 2003
Selecting the target year
Analysis and measurement of the cascadability for 2R O/E/O wavelength converter
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 215~218
DOI : 10.3807/KJOP.2003.14.3.215
A 2R O/E/O wavelength converter is useful for bit rate transparency, though it has a limit on cascadability due to timing-jitter accumulation. In this paper, we propose a nonlinear signal model which is more practical than the commonly used sine wave model. With our model, we theoretically analyzed the effects of timing-jitter and the cascadability of a 2R O/E/O wavelength converter. To confirm the theoretical results, we measured the cascadability in a 40-km re-circulation loop for 10 Gb/s signal.
Measurement method for profiling residual stress of an optical fiber
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 219~223
DOI : 10.3807/KJOP.2003.14.3.219
A novel method was proposed for determining the residual stress profile of an optical fiber by using a modified polariscope. Measurement results of the axisymmetric residual stress for a conventional single-mode fiber were demonstrated by using this method. It was found that non-uniform stress is distributed in the cladding of the fiber. This means that large mechanical stress is induced as a function of temperature generated near the neck shape of the fiber preform.
Single-mode fiber depolarizer for WDM optical communications
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 224~229
DOI : 10.3807/KJOP.2003.14.3.224
We realized a depolarizer based on two 2
2 directional couplers and single mode optical fiber. A reduction method for the degree of polarization is demonstrated by using computer simulation, which is verified experimentally. The degree of polarization is -20 dB for the polarized input beam of spectral width less than 0.05 nm. The experimental results verify that the polarization noise, which is due to the change of the input polarization state, can be reduced by making the fiber-ring delay-line length greater thanthecoherencelengthofthesource.
A study of fiber optic intrusion sensor system using the speckle patterns
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 230~235
DOI : 10.3807/KJOP.2003.14.3.230
A fiber optic intrusion sensor system using the variations of speckle patterns was developed. The intrusion sensor system consisted of an analog unit, a digital control unit, and a DSP unit. Some experiments were carried out using a 500 m length optical fiber sensor. The system detected intruders without missing, and distinguished between cars and persons. When the intruders were cars, the discrimination probability was 100% and when the intruders were persons, the discrimination probability was 90%.
Lens system design for head mounted display using schematic eyes
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 236~243
DOI : 10.3807/KJOP.2003.14.3.236
We discussed the design of lens module schematic eyes equivalent to finite model eyes, which are used to model the human eye based on spherical aberration and Stiles-Crowford effect. The optical system for head mounted display (HMD) is designed and evaluated using lens module schematic eyes. In addition to a compact HMD system, an optical system with high Performance is required. To satisfy these requirements, we used diffractive optical elements and aspheric surfaces so that the color and mono-chromatic aberrations were corrected. The optical system for HMD is composed of 0.47 inch micro-display of SVGA grade with 480,000 pixels, a plastic hybrid lens for the virtual image, and the lens module schematic eyes. The designed optical system fulfills the current specifications of HMD: such as, EFL of 31.25 mm, FOV of 24H
30D degrees, and overall length of 59.1 mm. As a result, we could design an optical system useful for HMD; the system is expected to be comfortable while the user wears it.
Recording of larger object by using two confocal lenses in digital holography
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 244~248
DOI : 10.3807/KJOP.2003.14.3.244
When confocal lenses are applied to a digital holography system, the interference pattern of a larger object size can be recorded on CCD. The angle of incoming light to the CCD can be reduced by the ratio of the two focal lengths of confocal lenses. The recordable spatial frequency is limited by the unit cell size of the CCD. Therefore the spatial frequency of interference on the CCD is lowered by reduction of the incoming light angle. By using confocal lenses , another merit can be achieved that the area of the zero order diffraction is reduced by the square of the ratio of two focal lengths at the numerical reconstruction.
Optical encryption system using phase-encoded virtual image
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 249~254
DOI : 10.3807/KJOP.2003.14.3.249
In this paper, we propose an improved image encryption and decryption method using a phase-encoded virtual image and interference. An original image is simply decrypted by interfering a reference wave with the wave passing through a decrypting key and the encrypted image, where every image has grey level. The proposed encryption is performed by the multiplication of an encrypting key and a phase-encoded virtual image which dose not contain any information for the original image. Therefore even if unauthorized people analyze the encrypted image, they cannot reconstruct the original image. Also grey image encryption can improve the encryption level compared to binary image encryption. Computer simulation and optical experiments confirmed that the proposed technique is a simple for optical encryption.
Optical encryption and decryption technique using virtual image in frequency domain
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 255~259
DOI : 10.3807/KJOP.2003.14.3.255
In this paper, we propose an improved image encryption and decryption method using a virtual image and a joint transform correlator (JTC). The encrypted image is obtained by the Fourier transform of the product of a virtual-phase image and a random-phase image, and a Fourier transform of the decrypting key generated by the proposed phase assignment rule is used as the Fourier decrypting key. Based on the solution, the original image is reconstructed using JTC in the frequency-domain. The proposed method using a virtual image, which does not contain any information from the original image, prevents the possibility of counterfeiting by unauthorized people. And also the auto-correlation terms, which are the drawback of a JTC system, contribute to reconstructing the original image rather than to disturbing its identification. But because phase-only encryptions are sensitive to noise and scratches, phase errors can be generated in fabricating the encrypted image or the Fourier decrypting key so the errors that are responsible for degradation of the quality of the reconstructed image are analyzed and the solution is demonstrated. Computer simulations show the solution, and the proposed method is very useful for JTC architecture.
Noncontact optical system for measurement of displacement and vibration
Hwang, Woong ; Kwon, Jin-Hyuk ;
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 260~265
DOI : 10.3807/KJOP.2003.14.3.260
A noncontact optical system that can measure displacement or vibration of an object is designed by employing the oblique ray method. By using a single convex lens which serves as both the input and output lenses, we made the optical system very compact and reliable. In addition, the bandwidth of the vibration measurement is more than 100 KHz by using the position-sensitive detector as the beam position sensor. The resolution and capture range of the system are
, respectively. As a sample test, the vibrations of a speaker and a rotating compact disc surface were measured.
Application of the modified fast fourier transformation weighted with refractive index dispersion far an accurate determination of film thickness
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 266~271
DOI : 10.3807/KJOP.2003.14.3.266
The reflectance spectrum of optical films thicker than a few microns shows an intensity oscillation due to interference. Since the spectral period of the oscillation is inversely related to film thickness, the thickness of an optical film can be determined from the spectral frequency of the oscillation. For rapid data processing, the spectral frequency is obtained by use of a Fast Fourier Transformation technique. The conventional method of applying a Fast Fourier Transformation to the reflectance spectrum versus photon energy is modified so as to clear the ambiguity in choosing the proper effective refractive index value and to prevent the broadening of the Fourier transformed peak due to the refractive index dispersion. This technique of modified Fast Fourier Transformation is suggested by the authors for the first time to their knowledge. From the analysis of the calculated reflectance spectrum of a 30-
-thick dielectric film. it is shown to improve the accuracy in determining film thickness by a great amount. The improved accuracy of the modified Fast Fourier Transformation is also confirmed from the analysis of the reflectance spectra of a sample with 80-
-thick cover layer and 13-
-thick spacer layer on a PC substrate.
Analysis of patterned ITO layer of PDP thin films using spectroscopic ellipsometry
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 272~278
DOI : 10.3807/KJOP.2003.14.3.272
We studied patterned ITO layers of PDP thin films on glass substrates using spectroscopic ellipsometry. The optical property of ITO is expressed with the optical model based on two Lorentz oscillators. The effect of patterned ITO is calculated by taking the weighted average of reflectance in proportion to ITO coverage. The relative coverage of ITO is determined by using the model analysis of spectroellipsometric data. The difference of ITO coverage obtained by the best-fit model analysis of ellipsometric spectra to the expected one is critically examined and suggestions are made to minimize the observed discrepancy.
Theoretical and experimental analysis of modal gain in asymmetric multiple quantum well laser diodes
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 279~285
DOI : 10.3807/KJOP.2003.14.3.279
Wide- and flat-gain laser diodes were designed and fabricated from asymmetric multiple quantum well (AMQW) structures which consist of three compressively strained InGaAsP wells of different thicknesses. For a 400
-long lasers with as-cleaved facets, -1 ㏈ and -3 ㏈ gain bandwidth were 45 nm and 80 nm, respectively. For this AMQW structure, calculated gain spectra with various line broadening functions were compared with experimental results. We confirmed the calculated gain spectra using an asymmetric line broadening function were in good agreement with the measured data.
Design and Fabrication of Broad Gain Laser Diodes
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 286~291
DOI : 10.3807/KJOP.2003.14.3.286
Asymmetric multiple quantum well ridge waveguide laser diodes (AMQW RWG LDs) with a wide and flat gain spectrum were designed and fabricated. The operating parameters and gain spectra were measured and analyzed for uncoated and anti-reflection (AR) coated LDs. For AR coated 500 mm-long RWG LOs, the extremely flat gain spectrum over a spectral range of 90 nm was obtained at the current 75 ㎃.
A study on the lasing characteristics of diode-pumped, single-mode Nd:YVO
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 292~297
DOI : 10.3807/KJOP.2003.14.3.292
A diode-pumped single-mode Nd:YV
green laser was developed. Frequency doubling of the laser was achieved by using an intracavity KTP generated green beam (532 nm). By comparing the diode laser spectrum with absorption spectrum of the Nd:YV
crystal, we found optimal operating temperature of the diode laser. From output power measured for various mirror curvatures and cavity lengths, we found the optimal matching of TE
mode with the pump beam gives the best efficiency. When the pump power was 1.9 W, 80 ㎽ of TE
mode green beam was obtained. We tried to get a single longitudinal mode lasing as the fluctuation of the laser power was caused by the shift of longitudinal modes and the beating between the modes. We tested the intracavity etalon method and birefringent filter method for single mode operation. The etalon method resulted in the best single mode output power of 60 ㎽. The power fluctuation of the single-mode laser was reduced to 1/10 of that of the multi-mode laser.ser.
Single mode yield analysis of index-coupled DFB lasers above threshold for various facet reflectivity combinations
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 298~305
DOI : 10.3807/KJOP.2003.14.3.298
We have calculated the single mode yield of index-coupled (IC) DFB lasers above threshold for several kL, and facet reflectivity combinations, and investigated the correlation between those results and the single mode yield as a function of f number at the threshold. As a result, there is little correlation between the single mode yield above threshold and the single mode yield as a function of f number at the threshold. The single mode yields above threshold for kL of 0.8 and 1.25 is larger than those for kL, of 2 and 3 due to the spatial hole burning effect. Also, we have investigated the effect of the reflectivity of the AR facet on the single mode yield for AR-HR and AR-CL combinations. For AR-HR combinations, the single mode yield increases as the reflectivity of the AR facet decreases. However, for AR-CL combinations, the reflectivity of the AR facet for the largest single mode yield exists. In the single mode yield calculations for IC DFB lasers in this paper, the single mode yield for kL of 0.8 with AR(1％)-HR combination is largest above threshold.
The characteristics and optimal modeling of input source for optical device using thin film filter in optical telecommunication network
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 306~311
DOI : 10.3807/KJOP.2003.14.3.306
In this paper, we modeled the incident beam in order to analyze and evaluate the optical thin film device for wavelength division multiplexing in optical telecommunication network. As applied ray tracing method to the optical path, we were compared the accuracy of coupling efficiency simulated by two modeling methods. In the results of sinulation, ceil modeling method was preferred to annual modeling method in micro-optic device because of accuracy for coupling efficiency and Gaussian intensity distribution. In the results of optimal simulation for optical device using thin film filter, the distance (d1) between optical fiber and GRIN lens, the distance (d2) between GRIN lens and thin film filter and the coupling efficiency were 0.24 mm, 0.25 mm and -0.11 ㏈ respectively. As d2 was displaced at 0.25 mm and d1 was varied in order to evaluate the optimal value, d1 and maximum coupling efficiency were 0.24 mm and -0.35㏈, respectively. Then the results of experiment were corresponded to that of optimal simulation by cell modeling and it was possible to analyze the performance for optical device using thin film filter by the simulation.
Three-dimensional micro photomachining of polymer using DPSSL (Diode Pumped Solid State Laser) with 355 nm wavelength
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 312~320
DOI : 10.3807/KJOP.2003.14.3.312
The basic mechanistic aspects of the interaction and practical considerations related to polymer ablation were briefly reviewed. Photochemical and photothermal effects, which highly depend on laser wavelength have close correlation with each other. In this study, multi-scanning laser ablation processing of polymer with a DPSS (Diode Pumped Solid State) 3rd harmonic Nd:YVO
laser (355 nm) was developed to fabricate a three-dimensional micro shape. Polymer fabrication using DPSSL has some advantages compared with the conventional polymer ablation process using KrF and ArF laser with 248 nm and 193 nm wavelength. These advantages include pumping efficiency and low maintenance cost. And this method also makes it possible to fabricate 2D patterns or 3D shapes rapidly and cheaply because CAD/CAM software and precision stages are used without complex projection mask techniques. Photomachinability of polymer is highly influenced by laser wavelength and by the polymer's own chemical structure. So the optical characteristics of polymers for a 355 nm laser source is investigated experimentally and theoretically. The photophysical and photochemical parameters such as laser fluence, focusing position, and ambient gas were considered to reduce the plume effect which re-deposits debris on the surface of substrate. These phenomena affect the surface roughness and even induce delamination around the ablation site. Thus, the process parameters were tuned to optimize for gaining precision surface shape and quality. This maskless direct photomachining technology using DPSSL could be expected to manufacture tile prototype of micro devices and molds for the laser-LIGA process.
1.55 μm continuous tuning external cavity laser
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 321~326
DOI : 10.3807/KJOP.2003.14.3.321
We constructed grating- tuned external cavity semiconductor lasers using Littman and Littrow configuration, for which the wavelengths are tuned by rotation of the grating. This wavelength tunable semiconductor laser is one of the main devices of WDM optical communication. In Littman configuration, the wavelength range of about 60 nm (The C- and L-band range of 1,530~1,590 nm) was obtained by changing the incidence angle of the grating about
from the incidence angle of 70
. In the 40 nm tuning range, the output power variation was less than 1.25 ㏈ and the side mode suppression ratio(SMSR) was 32 ㏈. In Littrow configuration (The incidence angle and the first order diffraction angle is the same, i.e.
), the wavelength tuning range was about 80 nm for the same conditions used in Littman configuration except the incidence angle (
). In 60 nm tuning range, the output power variation was less than 1.5 ㏈ and SMSR was 35 ㏈.
Fabrication and lasing characteristics of tunable Butt-coupled DBR-LD
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 327~330
DOI : 10.3807/KJOP.2003.14.3.327
We present the fabrication and measured performance of a wavelength tunable Butt coupled DBR-LD. An average coupling efficiency between active layer and passive waveguide layer was measured over 85％per facet, and the average threshold current was 21 ㎃ for the waveguide integrated DBR laser. High output power of Butt coupled DBR-LD was obtained over 25 ㎽. As high as 25 ㎽ of output power was achieved by the butt coupled method. The maximum wavelength tuning range is about 7.4 nm, and the side mode suppression ratio was more than 40 ㏈ using 1.3
InGaAsP waveguide layer.
Fabrication and optical characteristics of 50 ㎓ narrow band pass filter for fiber optical communication using dual ion beam sputtering technique
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 331~337
DOI : 10.3807/KJOP.2003.14.3.331
This paper represents 50 ㎓ narrow band pass filters for fiber optical communication fabricated by dual ion beam sputtering method. We have analyzed the characteristics of the TA
single layers in order to optimize the process conditions for the 50 ㎓ narrow band pass filters, and controlled the film thickness uniformity to less than 0.1 nm deviation by dual peak spike filter pre-deposition. We designed and fabricated 50 ㎓ narrow band pass filters that consist of 216 layers including 4 cavities based on quarter wave optical thickness. Class substrates with high thermal expansion coefficients were used to reduce the film stress. Anti-reflection coating at the rear side of the substrate was also needed to reduce the optical thickness errors of the Optical Monitoring System caused by multiple beam interference between the front side and the rear side of substrate. The optical characteristics of this 50 ㎓ narrow band pass filters are insertion loss of 0.40 ㏈, pass band ripple of 0.20 ㏈, and pass bandwidth at -0.5 ㏈ of 0.20 nm. and isolation bandwidth at -25 ㏈ of 0.6 nm, which satisfy specifications of dense WDM system in fiber optical communications.tions.
Stimulated Brillouin scattering in optical fiber for pulsed lights compared to continuous wave lights
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 338~342
DOI : 10.3807/KJOP.2003.14.3.338
We have studied the properties of stimulated Brillouin scattering (SBS) in an optical fiber using optical pulses and continuous wave light. We find that the thresholds for SBS are the same when the averaged power of pulse light is the same as the power of cw light. From this result, the SBS threshold of pulse light can be deduced from that of continuous wave light, which can be obtained easily and accurately.
Transport and optical properties of indium tin oxide films fabricated by reactive magnetron sputtering
Korean Journal of Optics and Photonics, volume 14, issue 3, 2003, Pages 343~348
DOI : 10.3807/KJOP.2003.14.3.343
Indium tin oxide (ITO) thin films (170 nm) were grown by DC magnetron sputtering deposition on Coming glass substrates without a post annealing. The electrical transport and optical properties of the films have been investigated as a function of deposition temperature
) and oxygen partial pressure
torr). Films were deposited from a high density (99% of theoretical density) ITO target (I
= 90 wt% : 10 wt%) made of ITO nano powders. With an increase of
the electrical resistivity p of ITO thin films was found to decrease, but the mobility
was found to increase. The carrier density nu shows the maximum value of 6.6
. At fixed Is, with an increase of the oxygen partial pressure,
were found to decrease, but p was found to increase. The minimum resistivity and maximum mobility values of the ITO films were found to be 0.3 mΩ.cm and 39.3
/V.s, respectively. The visible transmittance of the ITO films was above 80%.. 80%..