• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.33A no.5
• /
• pp.132-141
• /
• 1996

The pixelated phase grating has been studied as a kind of diffraction gratings splitting and input beam into multiple spots. It consists of regular size cells which produce phase delays, and each cell provokes the phase delay up to sixteen levels. We have compared and analyzed the characteristics of multi-level phase gratings, laying streess on efficiency and resulted pattern. Experimental resutls obtained form fabricated grating have been presented, and the real-time method using a liquid-crystal spatial light modulator has been demonstrated through experiments. Gratings making meams with specific intensities have been designed and optical images have been generated by them. In order to specific intensities have been designed and optical images have been genrated by them. In order to decide the phase delay of each cell, optimization conditon consists of diffraction efficiency and target values. One period of phase gratings fabricated with surface relief was less than 256${\mu}m{\times}256{\mu}m$ and size of each cell was 1${\mu}m{\times}1{\mu}m$ surface relief grating has been made by coating photoresist on the glass plate, writing information pattern by Ar laser and developing it. in the experiment for real-tiem processing liquid-crystal display of epson video projector has been used.

• Korean Journal of Optics and Photonics
• /
• v.17 no.1
• /
• pp.18-22
• /
• 2006

The transmission characteristics of multiply cascaded phase-shifted long-period fiber gratings(LPFGs) were investigated theo-retically and experimentally. Their passband can be changed by increasing the number of p-shifted LPFGs. When two p-shifted LPFGs with different grating lengths are cascaded in series, the bandwidth of the rejection band and passband can be controlled by the pristine characteristics of two gratings. We also investigate the transmission characteristics of phase-shifted LPFG by exposing the half of LPFG region to UV laser. The transmission characteristics strongly depend on the initial coupling strength of the LPFG.

• Korean Journal of Optics and Photonics
• /
• v.15 no.6
• /
• pp.490-494
• /
• 2004

Bragg gratings were fabricated in Ge-doped silica planar lightwave circuits (PLC) for different writing conditions to study the growth characteristics. The refractive index modulation of the gratings grew in the PLC with total fluence F according to the power law $\Delta$n=A $F^{B}$. The characteristics of the PLC gratings formed for external cavity lasers match closely to those predicted by the power law. The oscillation spectra of the FP-LD with a Bragg grating grown in the PLC waveguide were also presented.d.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.21 no.3
• /
• pp.39-45
• /
• 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 Institute of Electronics Engineers of Korea SD
• /
• v.40 no.4
• /
• pp.21-26
• /
• 2003

In this paper, a channel spacing-tunable sampled fiber gratings(SFGs) is proposed, and analytically and experimentally investigated. The channel spacing of the proposed SFGs can be tuned by simply changing the period of the external pressure on the fiber Bragg gratings(FBGs). The channel spacing of 1.4nm was tuned to 0.8nm by changing the pressure period from 580${\mu}{\textrm}{m}$ to 1000${\mu}{\textrm}{m}$ The experimental results agree well with the theoretical results.

• Korean Journal of Optics and Photonics
• /
• v.5 no.1
• /
• pp.45-50
• /
• 1994

We have developed an algorithm of designing the binary phase gratings for even-numbered spot arrays which selectively cancel or suppress the unwanted even orders. Principles and properties which control the speed of the optimization algorithm are presented, and the results of the designed gratings are illustrated up to $1{\times}2에서 1\times}20$ array.

• Korean Journal of Optics and Photonics
• /
• v.15 no.6
• /
• pp.485-489
• /
• 2004

We demonstrated numerically that both the chromatic dispersion and the dispersion slope could be compensated by using purely phase-sampled superstructure fiber Bragg gratings provided with chirp of coupling coefficient along the wavelength axis. Also, we propose a purely phase-sampled Bragg grating for dispersion and dispersion slope compensation by introducing a chirp in coupling coefficient and sampling function. The bandwidth of all reflected channels can be equalized.

• Korean Journal of Optics and Photonics
• /
• v.5 no.4
• /
• pp.439-444
• /
• 1994

When diffraction by arbitrary two-dimensional surface-relief dielectric gratings is analyzed using the rigorous three-dimensional vector coupled-wave analysis, it is found that the matrix eigenvalue problem pertaining to the analysis can always be simplified to that for a matrix which has the dimension of a quarter of the original, so that computing time and memory requirements for computer may be greatly reduced. However this kind of simplification can not be obtained in the case of volume diffraction gratings. tings.

• Journal of the Optical Society of Korea
• /
• v.13 no.2
• /
• pp.294-298
• /
• 2009

In this paper we proposed a new Bragg grating waveguide in order to improve reflectivity and to achieve compactness. Bragg gratings with various thicknesses were engraved in the middle of the core layer with a length of 3 mm. For the sake of cost-effectiveness, the $3^{rd}$ order Bragg grating waveguides were fabricated via conventional photolithography. The maximum reflectivities for the fixed width waveguide of $6{\mu}m$ with the 0.1 and $0.3{\mu}m$-thick Bragg gratings were, -13.14 and -6.25 dB, respectively, and the Bragg wavelengths were 1562.28, 1564.10 nm, respectively. A slight increase in the Bragg grating thickness can result in a remarkable reduction in the length of the Bragg grating waveguide with a fixed reflectivity.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.11
• /
• pp.2723-2729
• /
• 1993

Moire principles are applied to the measurement of the spindle radial error motion. As opposed to conventional techniques, no master cylinder or ball is needed in the measurement so that the offset and out-of-roundness errors of the master can be inherently eliminated. Two periodic circular gratings are used, one is made on the spindle and the other is held stationary on the reference frame. When the two gratings are seen superimposed during spindle rotation, an interference fringe pattern is observed from which the information on the eccentricity between the two gratings can be extracted with high precision. The optical design and fringe analysis techniques of a prototype measurement system are described in detail with exemplary measurement results.