• Journal of the Optical Society of Korea
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• v.18 no.6
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• pp.685-690
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• 2014

Microholographic gratings were prepared on an aluminum oxide ($Al_2O_3$) surface using a 140-fs pulse at a center wavelength of 800 nm. The $Al_2O_3$ was deposited on a silicon wafer and on indium tin oxide glass to a thickness of approximately 25 nm using an atomic layer deposition process. The silicon wafer substrate exhibited reflection-type gratings that were measured as a function of the incidence angle. The diffraction efficiency of the fabricated gratings was measured, with a maximum diffraction efficiency of 45% at an incidence angle of approximately $30^{\circ}$.

• Journal of the Optical Society of Korea
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• v.20 no.5
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• pp.575-578
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• 2016

The thermal endurance of fiber Bragg gratings (FBGs), written with the aid of 193-nm ArF excimer laser irradiation on H₂-loaded Ge/B codoped silica fiber, and pretreated with a CO₂ laser and a subsequent slow cooling process, is investigated. These treated gratings show relatively less degradation of grating strength during the thermal annealing procedure. The thermal decay characteristics of treated and untreated fiber, recorded over a time period of 9 hours, have been compared. The effect on the Bragg transmission depth (BTD) and the center-wavelength shift, as well as the growth of refractive-index change during the grating inscription process for both treated and untreated fiber, are analyzed.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.1
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• pp.6-10
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• 2001

In this study, we investigated the optical properties of sub-wavelength a-Si thin film transmission gratings, especially the polarization effect, the phase difference and the birefringence by using linearly polarized He-Ne laser beam (632.8nm). The a-Si transmission grating of the thickness $of < 0.1 \mum$ with four-type period($\Lambda = 0.4 \mum and 0.6 \mum$ for sub-wavelength and $\Lambda = 1.0 \mum and 1.4 \mum$ for above-wavelength) on quartz substrates have been fabricated using 50 KeV Ga+ Focused-Ion-Beam(FIB) Milling and $CF_4$Reactive-Ion-Etching(RIE) method. Finally, we obtained the trating array of a-Si thin film with a period $0.4 \mum, 0.6 \mum, 1.0 \mum, 1.4 \mum$ which have nearly equal finger spacing and width, sucessfully. Especially, for gratings with $\Lambda = 0.6 \mum(linewidth=0.25 \mum, linespace=0.35\mum), the \etamax at \theta_в=17.0^{\circ}$ is estimated to be 96%. As the results, we believe that the sub-wavelength grating arrayed a-Si thin film has the applicability as the optical device and components.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.1
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• pp.225-230
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• 2017

In this paper, a highly efficient GMR(guided-mode resonant) color filter is proposed and implemented. The GMR color filter consists of $Si_3N_4/air$ layers containing complementary fixed and mobile gratings. The device is designed using RETT(rigorous equivalent transmission-line theory) and a grating structure operating in subwavelength. The numerical result reveals that the color filter has a tuning capability of about 35 nm over the $0.45{\mu}m{\sim}0.55{\mu}m$ range for blue-green color and across $0.6{\mu}m{\sim}0.7{\mu}m$ range for red color. Furthermore, The color filters have a spectral bandwidth of about 8 nm with efficiencies of 99%, 98%, and 99% at the center wavelength of blue, green, and red color, respectively, and these are higher efficiencies than reported in the literature previously.

• Journal of the Korean Graphic Arts Communication Society
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• v.29 no.3
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• pp.17-30
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• 2011

The polarizer is an important optical element used in a variety of applications. Nano-wire grid polarizers in the form of sub-wavelength metallic gratings are an attractive alternative to conventional polarizers, because they provide high extinction ratio. This study has been carried out to fabrication of the 17inch area size nano-wire grid polarizer(NWGP) The master for NWGPs with a pitch of 200nm and the area size $730mm{\times}450mm$ were fabricated using laser interference lithography and aluminum sputtering and wet etching. And The NWGP fabrication process was using by the Roll to-Roll UV imprinting and was applied to flexible PET film. The results were a transmission of light (Tp) 46.7%, reflectance (Rs) 40.1% and Extinction ratio of above 16 for the visible light range.

• The Journal of the Convergence on Culture Technology
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• v.6 no.3
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• pp.419-425
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• 2020

In this paper, when a refractive index grating and a gain grating are simultaneously present in a DFB (Distributed Feedback) laser for a 1.55 um wavelength with two mirror surfaces without an anti-reflective coating, an analysis program was developed to determine the beam distribution of the oscillation mode in the longitudinal direction. As the phases of the index and gain gratings on the mirror faces are varied, the lasing gain and the beam profiles |R(z)| and |S(z)| of the lasing mode with the emitted power ratio P_l/P_r are analyzed and examined in case of δL<0. In order to reduce the threshold current of a oscillation mode and enhance the frequency stability, κL should be greater than 8, regardless of the grating phase values at the mirror surface.

• Korean Journal of Optics and Photonics
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• v.18 no.6
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• pp.383-388
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• 2007

A color filter was demonstrated incorporating a patterned metal grating in a quartz substrate. The filter is created in a metal layer perforated with a symmetric two-dimensional array of circular holes, with the pitch smaller than the wavelength of the visible light. A finite-difference time-domain simulation was performed to analyze the device by investigating the effect of structural parameters like the grating height, the period, the hole size, and the refractive index of the hole-filling material on its performance. The device performance was especially optimized by controlling the refractive index of the material comprising the holes of the grating. And two different devices were fabricated by means of the e-beam direct writing with the following design parameters: the grating height of 50 nm, the two pitches of 340 nm for the red color and 260 nm for the green color. For the prepared device with the period of 340 nm, the center wavelength was 680 nm and the peak transmission 57%. And for the other device with the pitch of 260 nm, the center wavelength was 550 nm and the peak transmission was 50%. The filling of the hole with a material whose refractive index is matched to that of the substrate has led to an increase of ${\sim}15%$ in the transmission efficiency.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.5
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• pp.151-156
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• 2020

To analyze the diffraction properties of optical signals and the significant impacts of tapered sidewall profile at periodic trapezoidal 2D diffraction gratings, Toeplitz dielectric tensor is first defined and formulated by 2D spatial Fourier expansions associated with trapezoidal profile. The characteristic modes in each layer is then based on eigenvalue problem, and the complete solution is found rigorously in terms of modal transmission-line theory (MTLT) to address the pertinent boundary-value problems. Based on those one, the numerical analysis is performed on how the tapered side profile of grating structures with trapezoidal refractive index distribution affects the design of a sub-wavelength grating reflector. The numerical results reveal that this tapered sidewall profile plays a critical role in determining the reflection bandwidth, the average reflectance, and the band edge.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.5
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• pp.31-38
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• 2000

We propose a new photorefractive demultiplexer(DMUX) which can select the 16 channel signal in WDM optical communication system using the wavelength selectivity and the demultiplexing property through multiple recording of holographic volume grating in photorefractive Fe-LiNbO$_{3}$ crystal. For the multiple writing of the 16 channels having uniform diffraction efficiency, the rotation multiplexing technique and the exposure time schedule are used. Designed DMUX has the 16 channels with 0.5nm spacing between 670nm and 677.5nm and the bandwidth of 0.16nm. From the experimental results, the diffraction efficiency of each channel is 8.3 $\pm$0.62%, the optical loss from fresnel reflection and absorption on the crystal is 0.4cm-1, the 3㏈ bandwidth is 0.16 $\pm$0.005nm and the channel spacing is 0.46~0.5nm.

• Korean Journal of Optics and Photonics
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• v.19 no.1
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• pp.20-24
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• 2008

A color filter was proposed and demonstrated by incorporating a subwavelength patterned 1-dimensional grating in poly silicon. It was produced by employing the laser interference lithography method, providing much wider effective area compared to the conventional e-beam lithography. A $SiO_2$ layer was introduced on top of the silicon grating layer as a mask for the etching of the silicon, facilitating the etching of the silicon layer. It was theoretically found that the selectivity of the filter was also improved thanks to the oxide layer. The parameters for the designed device include the grating pitch of 450 nm, the grating height of 100 nm and the oxide-layer height of 200 nm. As for the fabricated filter, the spectral pass band corresponded to the blue color centered at 470 nm and the peak transmission was about 40%. Within the effective area of $3{\times}3mm^2$, the variation in the relative transmission efficiency and in the center wavelength was less than 10% and 2 nm respectively. Finally, the influence of the angle of the incident beam upon the transfer characteristics of the device was investigated in terms of the rate of the relative transmission efficiency, which was found to be equivalent to 1.5%/degree.