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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Korean Journal of Optics and Photonics
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Journal DOI :
Optical Society of Korea
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Volume & Issues
Volume 13, Issue 6 - Dec 2002
Volume 13, Issue 5 - Oct 2002
Volume 13, Issue 4 - Aug 2002
Volume 13, Issue 3 - Jun 2002
Volume 13, Issue 2 - Apr 2002
Volume 13, Issue 1 - Feb 2002
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Wavelength-division multiplexing channel isolation filter using a side-polished fiber coupler
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 461~466
DOI : 10.3807/KJOP.2002.13.6.461
Fiber-optic comb filters using a side-polished fiber coupler are proposed as multi-channel isolation filters on wavelength division multiplexing systems. We have demonstrated that the coupling efficiency between two waveguides is improved by the intermediate coupling layer in spite of the decrease of the optical power transfer between two waveguides due to the high-order modes of the overlay waveguide coupled with the side-polished single-mode fiber. When LiNbO
with a 200-
-thickness was applied as a planar-overlay-waveguide, the comb filtering characteristics with a 4 nm-channel-spacing were achieved and the maximum power coupling occurred at the 1-
-thickness and the refractive index in range 1.52 to 1.53 of an intermediate coupling layer. If the intermediate coupling layer is optimized, an extinction ratio with more than 20 dB can be obtained. These experimental results are in good agreement with the BPM simulation.
Polarization-independent temperature sensor using cladding layers of the overlay waveguide coupled with a side-polished fiber
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 467~472
DOI : 10.3807/KJOP.2002.13.6.467
In this paper, we propose a polarization-insensitive temperature sensor using a thermo-optic effect of the upper and (or) lower cladding of a planar waveguide in contact with a side-polished fiber. A microscope cover glass with thickness of a 170
is adopted as an overlay waveguide because this waveguide opposes sudden temperature change and ensures polarization-insensitive responses. The measured polarization-dependence loss is less than 0.3 dB. The temperature can be detected as a result of the shift in coupling wavelength of the sensor. We investigate the shift in coupling wavelength as a function of the temperature variation with respect to the different thermo-optic coefficients of lower and upper claddings. We also show that the temperature sensitivity of the device can be easily controlled by the thermo-optic coefficients of lower and upper claddings of the overlay waveguide.
Leaky modes of circular slab waveguides: modified airy functions
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 473~478
DOI : 10.3807/KJOP.2002.13.6.473
Circular slab waveguides are conformally mapped into straight waveguides. In the outer cladding region with monotonically increasing index profile, modified Airy functions (MAF) of traveling-wave form are introduced to express the leaky mode. Field distributions and losses calculated by the proposed method are compared with those obtained by the WKB (Wentzel-Kramers-Brillouin) method. Detailed numerical examples are presented and compared with the conventional WKB methods, demonstrating our method not only allows a converging field at turning points but also guarantees fine accuracy.
Vector analysis for multimode-interference power splitter with an arbitrary splitting ratio
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 479~485
DOI : 10.3807/KJOP.2002.13.6.479
We propose a vector analysis for designing multimode-interference power splitters, which can show an arbitrary splitting ratio. Power splitting is a fundamental characteristic in integrated optical circuits and its value would be multiplied for many applications if the splitting ratio could be selected freely. Since the vector analysis utilizes a graphical method based on the previously-reported mathematical results of multimode interference, it shows an excellent advantage especially for designing power splitters with an arbitrary splitting ratio.
A study on 1 & 2 dimensional minimum mean-squared-error equalization for digital holographic data storage system
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 486~492
DOI : 10.3807/KJOP.2002.13.6.486
In this paper. we presented 1 & 2 dimensional minimum mean-squared-error (MMSE) equalization scheme in a digital holographic data storage system to improve bit-error-rate (BER) and to mitigate inter-symbol interference (ISI) which were generated during the data storage and retrieval processes. We showed experimentally for ten data pages retrieved from the holographic storage system that BER and signal-to-noise ratio (SNR) were improved by adopting MMSE equalization.
A study on correlation-based fingerprint recognition method
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 493~500
DOI : 10.3807/KJOP.2002.13.6.493
Fingerprint recognition is concerned with fingerprint acquisition and matching. Our research was focused on a fingerprint matching method using an inkless fingerprint input sensor at the fingerprint acquisition step. Since an inkless fingerprint sensor produces a digital-image-processed fingerprint image, we did not consider noise that can happen while acquiring the fingerprint. And making the user attempt fingerprint input as random, we considered image distortion that translation and rotation are included as complex. NJTC algorithm is used for fingerprint identification and verification. The method to find the center of the fingerprint is added in the NJTC algorithm to supplement discrimination of fingerprint recognition. From this center point, we decided the optimum cropping size for effective matching with pixels and demonstrated that the proposed method has high discrimination and high efficiency.
The characteristics of optical CDMA systems using PN codes and FBGs for ultra-fast optical access networks
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 501~505
DOI : 10.3807/KJOP.2002.13.6.501
We have numerically analysed the effects of the light sourer spectral power distortion in an optical CDMA system using PN codes and FBGI for ultra-fast multi-access optical networks. The interference between two CDMA channels decreases with an increase in the code length and the .simultaneous access number is equal to the code length in the region of 0 to 15% spectral power distortion. As a result, the spectral power distortion with optical spectrum is very important in designing the optical CDMA systems.
Optical system design for stereoscopic video-recorder
Hong, Kyung-Hee ;
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 506~509
DOI : 10.3807/KJOP.2002.13.6.506
An optical system for a stereoscopic video recorder is designed with the field of view 42
and effective diameter 22 mm. We can use it by attaching it to the front lens of any video camera or camcorder to record a stereoscopic scene. This system is a double Kepler type afocal system to make the image erect and a bi-ocular type to record and display the stereoscopic scene. The optical tube length is folded with several flat mirrors and a beam splitter to be compact. This optical system is composed of 4 groups of lenses and each group serves as a relay lens for minimizing the vignetting effect. Whole field stereoscopic scenes may be captured by perpendicularly polarized alternated recording with a chopper and two perpendicular polarizers, without any loss of light energy. The displayed images may be seen stereoscopically with polarized spectacles and are kinetic because of an afterimage effect.
A time delay measurement of a chirped fiber grating by using bidirectional modulation of an optical intensity modulator
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 510~514
DOI : 10.3807/KJOP.2002.13.6.510
A simple method for a time delay measurement of a chirped fiber grating by using bidirectional modulation of a Mach-Zehnder modulator has been proposed. The bidirectionally modulated light with time difference makes an interference fringe in the RF domain. The time delay of a chirped fiber grating can be obtained by measuring the period of the RF interference fringe for different wavelengths. We have measured the time delay of a chirped fiber grating with a chirped length of 5 cm and a bandwidth of 3.16 nm. The average slope of the time delay has been measured to be 183 ps/nm and its uncertainty has been less than
The variation of optical pass length between incident and reflective beam in multilayer thin film
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 515~520
DOI : 10.3807/KJOP.2002.13.6.515
The variation of the optical pass length between incident and reflective beam in a multilayer thin film reflection mirror is investigated. This variation is caused mainly by environmental parameters around the optical system, such as the air pressure, temperature, humidity and
concentration. In this paper, a new method for measuring optical pass length variation is proposed. This optical pass length is measured against the above parameters by experiment. From the experimental results, it is clarified that the optical pass length is mostly effected by humidity changes.
Error analysis and performance test of the volumetric interferometer for three dimensional coordinate measurements
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 521~529
DOI : 10.3807/KJOP.2002.13.6.521
We have recently proposed the new concept of a phase-measuring volumetric interferometer that enables us to accurately measure the xyz-coordinates of the probe without metrology frames. The interferometer is composed of a movable target and a fixed photo-detector array. The target is made of point diffraction sources to emit two spherical wavefronts, whose interference is monitored by an array of photo-detectors. Phase shifting is applied to obtain the precise phase values of the photo-detectors. Then the measured phases are fitted to a geometric model of multilateration so as to determine the xyz-location of the target by minimizing least square errors. The proposed interferometer has been designed and built with a volumetric uncertainty of less than 1.0
within a cubic working volume of side 120 mm. Here, in this paper, we also present error sources, an evaluated uncertainty, and test results from the prototype system. The self-calibration of two-dimensional precision metrology stages is applied to test the performance of the interferometer.
High resolution heterodyne interferometric technique with AOM for measuring the thermal expansion
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 530~536
DOI : 10.3807/KJOP.2002.13.6.530
The accurate measurements of thermal expansion coefficients is one of the most important techniques required not only in material science but also in industries. A high precision interferometric dilatometer, using acoustic optical modulator, has been constructed and its performance has been tested. The system consists of a double-path optical heterodyne interferometer and a radiant heating furnace. This provides highly accurate length measurement, and allows rapid heating and cooling method for the specimen. A three longitudinal mode frequency stabilized He-Ne laser, using the secondary beat frequency, is constructed. Its stability is found to be
. The uncertainty in the length measurement is estimated to be of nanometer order in the range between room temperature to 1100 K.
Null computer generated hologram test for measurement of parabolic mirror
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 537~542
DOI : 10.3807/KJOP.2002.13.6.537
Null tests using two different kinds of null corrector have been discussed. A parabolic mirror was used as a surface under test. After designing, encoding, and fabricating the CGH (computer generated hologram), the null CGH test was performed. An autocollimation test was also performed using a flat mirror. The reliability of the null CGH test has been discussed by comparing the result obtained by both null tests.
Characteristics of two extended-cavity diode lasers phase-locked with a 9.2 CHz frequency offset
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 543~547
DOI : 10.3807/KJOP.2002.13.6.543
We have constructed two extended-cavity diode lasers which are phase-locked with a 9.2 GHz frequency offset. We adopted a digital servo circuit for the phase-locking. The relative linewidth of the phase-locked lasers was less than 2 Hz. Using the measured beat spectrum, we found the carrier concentration to be about 93 %. We measured phase noise and relative frequency stability of the lasers. The Allan deviation at the gate time of 20 s was
Characteristics of the Nd:YAG laser with stimulated brillouin scattering phase conjugate mirror
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 548~553
DOI : 10.3807/KJOP.2002.13.6.548
We have investigated the output characteristics of a Nd:YAG oscillator with a Stimulated Brillouin Scattering phase conjugation mirror (SBS-PCM). FC-75 is used as an SBS gain medium and Cr:YAG (T=50%) as a Q-switcher. The SBS-PCM consists of an SBS-cell and a simple plano-convex focusing lens system. For the case of not using a Q-switcher, an SBS-cell doesn't work as a phase conjugation mirror. For the case of using a Q-switcher, the energy characteristics remains nearly the same whether using the SBS-cell or not using it. The pulse width is reduced from 50 ns to 40 ns by an SBS-PCM. When the SBS-cell is used with a Q- switcher, the SBS-cell works very well as a phase conjugation mirror and its beam-profile is improved dramatically. And in order to explain the progression of beam-profile, we propose a simple model based on the nonlinear reflectivity of the SBS-PCM, whose reflectivity is dependent on the pumping intensity at the focal plane.
Research of Nd:LSB microchip laser
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 554~558
DOI : 10.3807/KJOP.2002.13.6.554
A new laser material, Nd:LSB
, lanthanum scandium borate), of microchip type was grown by the Czochralski pulling method, and tested for optical and lasing properties. Nd:LSB, able to be highly doped with
ions while maintaining good optical, chemical, mechanical properties, was compared to another Nd-type laser material. The absorption and fluorescence spectra, and fluorescence lifetime were measured, and the crystal structure was analyzed. The lasing characteristics were investigated by using Ti:sapphire laser as a pumping light source.
The three-dimensional temporal behavior measurement of light emitted from plasma display panel by the Scanned Point-Detecting System
Korean Journal of Optics and Photonics, volume 13, issue 6, 2002, Pages 559~563
DOI : 10.3807/KJOP.2002.13.6.559
We measure the 3-dimensional temporal behavior of the light emitted from the discharge cell of a plasma display panel (PDP) by using a scanned point detecting system. The light signal detected by a PM tube is sent to the oscilloscope, and the oscilloscope is connected to a PC with GPIB. From the resultant temporal behaviors, we could analyze the discharge characteristics of the panel with a Ne-Xe (4%) mixing gas at a 400 torr pressure. The top view of the panel shows that discharge moves from the inner edge of the cathode electrode to the outer cathode electrode, forming an arc shape. The side view of the panel shows that the light is detected up to 150
up the barrier rib. After a trigger pulse is applied, peak intensity is detected at 730 ns and peak intensity position is located at the center of the ITO electrodes.