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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 15, Issue 6 - Dec 2004
Volume 15, Issue 5 - Oct 2004
Volume 15, Issue 4 - Aug 2004
Volume 15, Issue 3 - Jun 2004
Volume 15, Issue 2 - Apr 2004
Volume 15, Issue 1 - Feb 2004
Selecting the target year
Measurement of oxygen isotope ratio using tunable diode laser absorption spectroscopy
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 1~5
DOI : 10.3807/KJOP.2004.15.1.001
Tunable diode laser absorption spectroscopy was performed for analysis of the H
O isotope ratio of a water sample which was enriched by the membrane distillation method. In order to improve the signal-to-noise ratio, the wavelength modulation spectroscopic method was used with a lock-in amplifier. The fringe noise could be suppressed by using the FFT (Fast Fourier Transform) lowpass filter and the optimization of the modulation depth of the laser frequency. The maximum deviation of
-value was measured to be
Center wavelength shift and the optical property stabilization in photopolymer according to the press
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 6~11
DOI : 10.3807/KJOP.2004.15.1.006
The playback wavelength shift and the optical property stabilization of the reflection type photopolymer OmniDex film are studied as a function of pressure. As the center wavelength is changed from 632 nm to 482 nm, the bandwidth is 27％ broadened and the diffraction efficiency deviation maintained lower than 10％. These results show that the proposed color tuning method minimizes the change of optical properties more than 50％ compared with the diffusion-based method as the center wavelength changed from 511 nm to 630 nm. The press-based color tuning method shows that it could be used to make holographic optical elements that operate at wavelengths where lasers are not readily available for reflection type holographic recording.
Improvement of extinction ratio of polarization independent very short vertical directional couplers with the double-sided deep-ridge waveguide structure
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 12~16
DOI : 10.3807/KJOP.2004.15.1.012
We show that the extinction ratio is improved using slight asymmetry in two core refractive indices of polarization independent very short vertical directional couplers with the double-sided deep-ridge (DSDR) waveguide structure. The optimum asymmetry with the maximum extinction ratio and the tolerance of the refractive index of core with the extinction ratio larger 1ha]1 30 ㏈ increase as the thickness of inner cladding layer and the two cores decrease due to the increase of the coupling strength between the two cores. Also, the device length and the tolerance of the device length with the extinction ratio larger than 30 ㏈ decrease as the thickness of the inner cladding layer and the two cores decrease due to the increase of the coupling strength between the two cores. We show that polarization independent vertical directional couplers with the DSDR waveguide structure with the device length less than 100
and the extinction ratio larger than 30 ㏈ could be implemented.
Widely tunable thulium-doped fiber laser anchored on 50-GHz ITU-T grid in S/S＋ band
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 17~21
DOI : 10.3807/KJOP.2004.15.1.017
We demonstrate an S/S＋band discretely tunable thulium doped fiber laser (TTDFL), anchored on a 50-㎓ ITU-T grid. Investigating the inversion analysis of the thulium doped fiber (TDF) in applying a dual wavelength (1.4 m and 1.5 m) pumping scheme, a laser whose tuning range covers most of the S/S＋band has been obtained. Within the wide 3-㏈ bandwidth of 65.1 nm, the output power of the tunable laser exceeds 6.1 ㏈m with very flat spectral profile and the number of DWDM channels generated is as large as 178. If we increase the subsidiary pump power to 22 ㎽, the bandwidth is expanded up to 66.2 nm. By controlling the temperature of the fine grid filter, we have also shown that the frequency locking capability of the laser can be improved. The laser developed in this work is expected to be utilized as a practical optical source providing reference wavelengths in the S/S＋band.
Design and analysis of a mode size converter composed of periodically segmented taper waveguide
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 22~27
DOI : 10.3807/KJOP.2004.15.1.022
In this paper, we designed a mode size converter to reduce coupling loss between optical waveguide and single mode fiber. The proposed mode converter is composed of periodically segmented tapered waveguide to achieve small size and easy fabrication. For the optimally designed mode size converter at 1550nm, the taper length is 500(equation omitted), the segmentation period 5ß:, the waveguide width of fiber contact section 1.3ß:, and duty cycle 0.95. The coupling loss of the optimized mode size converter is 0.33㏈/point, which is 1.27㏈/point lower than that without the mode size converter.
Analysis of side-polished fiber couplers with an intermediate-coupling layer and improvement of their coupling efficiency
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 28~33
DOI : 10.3807/KJOP.2004.15.1.028
An in-line fiber coupler, based on side-polished single-mode fibers covered with an intermediate coupling layer and a planar waveguide, is analyzed by modeling the interaction region as an equivalent multi-layered planar waveguide. The reflectance for the multi-layered structure with and without buffer layer is illustrated as a function of the refractive index and thickness of the overlay waveguides. When the refractive index of the overlay waveguides is greater than that of the fiber core, the conditions for the intermediate coupling layer to increase the power coupling from the fiber to the overlays is also explained. Through the experimental results using a LiNbO
planar waveguide, we show that the theoretical analysis is reasonable and in good agreement with the measured values.
Linear interrogation of fiber Bragg grating sensor array using time-delayed quadrature sampling technique
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 34~38
DOI : 10.3807/KJOP.2004.15.1.034
A fiber laser of which wavelength was scanned by an intra-cavity FP (Fabry-Perot) filter was used to interrogate a fiber Bragg grating strain sensor array. We calculated the wavelength variation of the fiber laser using quadrature signal processing with an unbalanced M/Z (Mach-Zehnder) interferometer and time-delayed sampling technique. The calculated wavelengths are mapped to corresponding temporal reflection peaks from the sensor array, which enables more accurate and stable interrogation without the problems caused by the FP filter`s nonlinear characteristics. Wavelength resolution of ∼20 pm was obtained in our experimental setup, which could have been greatly enhanced with faster phase modulation.
Computer simulation of the removal of the 0-th order diffraction by using fourier transform in digital holography
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 39~45
DOI : 10.3807/KJOP.2004.15.1.039
A computer simulation about removal of the 0-th order diffraction is achieved by using numerical reconstruction in digital holography and the Fourier transform method. A light intensity distribution hologram is generated through numerical calculation of the interference pattern. Additionally a phase hologram without the 0-th order diffraction is generated. The removal function for elimination of the 0-the order diffraction is introduced and the numerical reconstructions with several conditions for the removal of the 0-th order diffraction and the production of high quality numerically reconstructed images are tested and compared. The removal function is proven to be more effective at the suppression of the 0-th order diffraction compared with the DC suppression method.
Imaging with terahertz electromagnetic pulses
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 46~50
DOI : 10.3807/KJOP.2004.15.1.046
Images were acquired by the modulation of terahertz electromagnetic signals and compared by modulation frequencies. For the real-time acquisition of images a fast scanning method has been adopted utilizing a galvanometer. The acquired time domain waveforms were transformed into frequency domain data by fast Fourier transformations (FFT). We chose some frequency components to compare the resolution of images. The beam profiles at the focal position were measured by a knife-edge technique. Beam diameter was shown to decrease as the frequency increased. By scanning one- and two-dimensional samples a significant image enhancement was observed with the frequency increment. A nondesouctive imaging system using ㎔ electromagnetic pulses was also demonstrated.
Measurement of surface plasmon using near-field scanning optical microscope
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 51~55
DOI : 10.3807/KJOP.2004.15.1.051
Surface plasmons (SPs) are charge density oscillations that propagate along an interface between a dielectric and metal. In this paper, the electric field of SPs and the intereference of two SPs are observed by using Near-field Scanning Optical Microscope (NSOM). The excitation condition of SPs is changed as the optical tip approaches the metal surface, because the excitation condition of SPs is very sensitive to surface structures. To measure the microscope field of SPs, the distance between metal surface and optical tip must contain a specific interval.
Diffraction grating interferometer of large equivalent wavelength for flatness testing of rough surfaces
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 56~62
DOI : 10.3807/KJOP.2004.15.1.056
We present a diffraction grating interferometer of large equivalent wavelength specially designed for flatness testing of rough surfaces. Two transmission diffraction gratings are illuminated on the object under test by use of two measurement beams with different angles of incidence, which yields a large equivalent wavelength. This interferometer design minimizes unnecessary diffraction rays and the systematic error caused by the diffraction gratings, and provides a large working distance and easy alignment. To improve the measurement accuracy, phase shifting technique is applied and the equivalent wavelength error caused by defocus is calibrated. Test results obtained from mirror surfaces and machined rough surfaces are discussed.
Determination of optical constants for cholesteric liquid crystal films by using transmittance and reflectance spectra
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 63~67
DOI : 10.3807/KJOP.2004.15.1.063
We have obtained optical constants for cholesteric liquid crystal (CLC) films by fitting theoretical spectra of transmittance and reflectance with measured ones. Berreman`s 4
4 matrix approach was used for the calculation of theoretical spectra. The fitting method was applied to three samples with different reflection bands and fitted results of refractive indices for CLC samples were compared with measured ones for a parallel-aligned LC sample. It was found that the two results were in fairly good agreement within the error of the fitted results for the three CLC samples.
Study on flexure angle measurement of ring laser gryo and the improvement of flexure error
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 68~73
DOI : 10.3807/KJOP.2004.15.1.068
Flexure measurement of ring laser gyro was investigated by using an interferometer. A two-beam interferometer of Fiezo-fringe pattern obtained the flexure angle in 1-gravity acceleration and the higher acceleration environments. These environments were made with the addition of dummy mass to the ring laser gyro axis. The flexure angle change for 1-gravity acceleration change was measured as 2.37 arcsec/g with low repeatability error of 0.01 arcsec/g. The laser navigation system consisting of 3 flexure-reduced ring laser gyros showed the improvement of flexure error.
Servo control for shift-multiplexed holographic data storage by using a dome-type glass
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 74~78
DOI : 10.3807/KJOP.2004.15.1.074
We propose a servo control method using a dome-type glass in shift-multiplexed holographic data storage. We frist store live 2-D data by shift-multiplexing in a holographic disk with 5％ variation in their. diffraction efficiencies. During read-out of the stored data, the servo control using the dome glass correctly compensates mechanical errors of the disk; the error of
and run-out error of
. Use of the dome-type glass in servo control makes a pickup module more compact in size and easier to control than the previous method using parallel glass plate ［Sungphil Kim, et al., Hankook Kwanghak Hoeji, Vol. 14, No. 1, pp.58-64, 2003］.
Transmittance controlled photomasks by use of backside phase patterns
Park, Jong-Rak ; Park, Jin-Hong ;
Korean Journal of Optics and Photonics, volume 15, issue 1, 2004, Pages 79~85
DOI : 10.3807/KJOP.2004.15.1.079
We report on a transmittance controlled photomask with phase patterns on the back quartz surface. Theoretical analysis for changes in illumination pupil shape with respect to the variation of size and density of backside phase patterns and experimental results for improvement of critical dimension uniformity on a wafer by using the transmittance controlled photomask are presented. As phase patterns for controlling transmittance of the photomask we used etched contact-hole type patterns with 180" rotative phase with respect to the unetched region. It is shown that pattern size on the backside of the photomask must be made as small as possible in order to keep the illumination pupil shape as close as possible to the original pupil shape and to achieve as large an illumination intensity drop as possible at a same pattern density. The distribution of illumination intensity drop suitable for correcting critical dimension error was realized by controlling pattern density of the contact-hole type phase patterns. We applied this transmittance controlled photomask to a critical layer of DRAM (Dynamic Random Access Memory) having a 140nm design rule and could achieve improvement of the critical dimension uniformity value from 24.0 nm to 10.7 nm in 3