• Korean Journal of Optics and Photonics
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• v.9 no.5
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• pp.307-314
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• 1998

We have studied the effects of interface on polarization dependence of waveguide and designed the polarization independent 2-dimensional waveguides on InP for arrayed waveguide grating. To figure out the effects of interface on polarization dependence, we have solved the 1-dimensional wave equation using a transfer matrix method. It is shown that the birefringence becomes stronger as the number of interfaces increases. In order to design polarization independent 2-dimensional waveguides, we have used effective index method. The structures considered are ridge type, raised strip type, and buried type waveguide. In the cases of ridge and raised strip type, conventional effective index method was used. In the case of buried type corrected effective index method was used. We have determined the height and width of waveguides such that the waveguides become polarization independent.

• Journal of the Optical Society of Korea
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• v.7 no.4
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• pp.269-274
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• 2003

In this paper, a Gaussian apodization technique applied to a transmission volume hologram for holographic demultiplexer is proposed. The Gaussian apodized grating of 15 mm ${\times}$ 11mm size, $38{\mu}m$ thickness and 3.2 mm horizontal standard deviation of the Gaussian index modulation profile was fabricated. A 22-channel demultiplexer based on that grating has been optically demonstrated. The channel spacing, the interchannel cross-talk level and the channel uniformity of 0.8 nm, -30 dB and 1.5 dB, respectively, were obtained.

• ETRI Journal
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• v.26 no.6
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• pp.661-664
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• 2004

The thermal behavior of an arrayed-waveguide grating made of a silica/polymer hybrid waveguide was examined. We experimentally confirmed that the hybrid waveguide is effective to decrease the temperature and polarization dependence of the center wavelength owing to the negative thermo-optic coefficient of the refractive index and extremely low baking temperature of the polymer cladding. However, the detachment of the polymer cladding from the silica core, which took place either during a repeated heat cycle test or during long-term storage in atmosphere, was a serious problem for practical use.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.3
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• pp.39-45
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• 1984

Submicron gratings are fabricated holographically on thin film single mode and multimode waveguides. Thin film waveguides are made by spin-coating polyurethane solution on the substrates of microscope slide glass and Corning 7059 glass. In order to characterize thin film waveguides, the refract사e index and the thickness of thin films are measured by using the m-line spectroscopy. The fabricated gratings are tested as a grating coupler, a mode converter, and a beam splitter. Also chirped gratings are fabricated to observe beam expansion phenomena and thus the possibility of the wavelength demultiplexing.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.7
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• pp.205-215
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• 1996

We derive the analytic equations for the transmission gain spectrum of a phase shift controlled (PSC) DFB filters with complexed coupled gratings considering both facet reflections and the phase of gratings using the transfer matrix method. The number of parameters of the equations is reduced by using the parameter of effective phase shift defined by the sum of the phase shift in a PSC region the effect of both facets reflections and the effective phase shift on the transmission gain spectrum and verify the validity of those equations from the computer simulation results. Computer simulation results show the PSC DFB filter with a pure index coupled grating has the widest tunable range and that with a pure gain grating has the largest side mode suppression ratio.

• ETRI Journal
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• v.24 no.5
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• pp.341-348
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• 2002

We propose an asymmetric sampled grating laser and a multi-wavelength laser array associated with it. Asymmetric sampling periods combined with an index shifter make it possible to use first order reflection for lasing operations. With the structure of our design, we achieved a simple fabrication procedure as well as a high yield without using complex and time-consuming e-beam lithography for multi-period gratings. We analyzed the effect of mirror coating by numerical analysis to improve single mode and power extraction performance. By using high reflection-antireflection coatings, we obtained high power extraction efficiency without degradation of the single mode property. For the multi-wavelength laser array, to gain wavelength control, we varied the sampling periods from one laser to an adjacent laser across the array. With this approach, we showed the feasibility of an array of up to 30 channels with 100 GHz wavelength spacing.

• Journal of the Optical Society of Korea
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• v.3 no.2
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• pp.41-46
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• 1999

Spatial and temporal dynamics arising in a photorefractive crystal(BaTiO3) during the process of double phase conjugation was studied experimentally. We studied the dynamical effects caused by the buildup of the diffraction grating and turn on of phase conjugated beams, as well as the spatial effects caused by the finite transverse coupling of beams and the propagation direction of beams. We observed conical emission in DPCM. We believe that various temporal and spatial instabilities are due to movement of the nonlinear grating. For a real beam coupling and constructive interaction of interference fringes in the crystal, we observed steady, periodic, irregular temporal behavior. And, by the calculation of the correlation index, we found that the spatial correlation decreased as the transverse interaction region was increased.

• Journal of the Optical Society of Korea
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• v.1 no.1
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• pp.26-35
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• 1997

Rigorous coupled-wave analysis (RCWA) with a simplified eigenvalue problem is used to investigate the an-tireflective property of one-dimensional surface-relief gratings such as binary gratings, triangular gratings and gratings with triangle-like surface profiles. The convergence of RCWA is investigated by varying the number of layers and the number of space-harmonics used in the computation. For unpolarized light normally incident on a medium of refractive index 1.64 from vaccum, a triangle-like grating shows the reflectivity of $1.6 {\times} 10^{-4}$ in contrast to a minimum reflectivity of $3.8 {\times} 10^{-3}$ for a binary grating. We also study the dependence of reflectivity on the wavelength, and on the angle of incidence for a groove shape and depth which result in minimum reflectivity.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.9
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• pp.624-633
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• 2001

Influence of the grating half-period fluctuation on the normalized coupling coefficient has been studied by an effective index transfer matrix method in quarter wavelength shifted(QWS) DFB lasers. The laser facets are assumed to be perfectly antireflection coated, and the period fluctuation is modeled by two correlated Gaussian random variables. In the presence of the random fluctuation in the grating period, effective normalized coupling coefficient is reduced because the in-phase feedback strength Is weakened. We have shown that the normalized coupling coefficient determined from the side mode spacing is less than the effective coupling coefficient, and the normalized coupling coefficient determined from the mode spacing or spontaneous emission spectrum does not properly represent the feedback strength of the grating.

• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.54-59
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• 2006

Biophotonic sensors based on polymer waveguide with Bragg reflection grating are demonstrated in this work. Waveguide Bragg reflectors were designed by using the effective index method and the transmission matrix method. The grating pattern was formed by exposing the laser interference pattern on a photoresist. On top of the inverted rib waveguide, the Bragg reflection grating was inscribed by the O2 plasma etching. In order to perform the bio-molecule detection experiment, a calixarene molecule was self-assembled on top of thin Au film deposited on the waveguide Bragg reflector. To measure the response of the sensor, several PBS solutions with different concentrations of potassium ion from 1 pM to $100\;{\mu}M$ were dropped on the sensor surface. The shift of Bragg reflection wavelength was observed from the fabricated sensor device, which was proportional to the concentration of potassium ion ranging from 1 pM to 108 pM.