• Korean Journal of Optics and Photonics
• /
• v.16 no.6
• /
• pp.508-515
• /
• 2005

We propose a fabrication method for refractive lens by variable velocity moving mask lithography and slit pattern. Distribution of exposure dose should be controlled for the curved photoresist surface that works as a refractive surface. We analyze theoretically the distribution of exposure dose by change of moving velocity, moving direction of mask and the shape of mask pattern, and confirm for the curved surface experimentally. The lens could have sag height of a few of hundreds ${\mu}m$, by using thick photoresist or Deep RIE process.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.2
• /
• pp.33-39
• /
• 2003

A new microlens fabrication technique, the excimer laser lithography is developed. This bases on the pulsed laser irradiation and the transfer of a chromium-on-quartz reticle on to the polymer surface with a proper projection optics system. An excimer laser lithography system with 1/4 and 1/20 demagnification ratios was constructed first, and the photoablation characteristics of the PMMA and Polyimide were experimentally examined using this system. For two different shapes of microlenses, a spherical lens and a cylindrical lens, fabrication techniques were investigated. One for the spherical lens is a combination of the mask pattern projection and fraction effect. The other for the cylindrical lens is a combination of the mask pattern projection and the relative movement of a specimen. The result shows that various shapes of micro optical components can be easily fabricated by the excimer laser lithography.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.5 no.3
• /
• pp.197-203
• /
• 2004

New lithography techniques are employed for the patterning of arbitrary shapes in nanometer scale. When, in the photolithography, the electromagnetic waves such as UV and X-ray are incident on the mask patterned in nanometer scale, the diffraction effect is unavoidable and degrades images of the mask imprinted on wafer. Only a convex lens is well-known Fourier transformer. It is possible to make the mask Fourier-transformed with the convex lens, even though the size of pattern on the mask is very large compared to the wavelength of electromagnetic wave. If the mask, modified according to new technique described in this paper, was placed at the front of the lens and was illuminated with laser beam, the nanometer-size patterns are only formed on the plane called Fourier transform plane. The new method presented here is quite simple setup and comparable with present and next generation lithographies such as UV/EUV photolithograpy and electron projection lithography when compared in attainable minimum linewidth. In this paper, we showed our theoretical research work in the field of Fourier optics, . In the near future, we are going to verify this theoretical work by experiments.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.62-62
• /
• 2010

Photonic quasi-crystals(PQCs) have been fabricated by a multiple-exposure nanosphere lithography (MENSL) method using the self-assembled nanospheres as lens-mask patterns. The multiple-exposing source is collimated laser beam and rotation, tilting system. The arrays of the PQCs exhibited variable lattice structures and shape the control of ratating angle ($\theta$), tilting angle ($\gamma$) and the exposure conditions. The used nanosphere size is upto the $1\;{\mu}m$. Images of prepared 2D PQCs were observed by SEM. We believe that the MENSL method is a suitable useful tool to realize the PQCs arrays of large area.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.23 no.3
• /
• pp.245-249
• /
• 2010

Two dimensional(2D) pair-photonic crystals (pair-PCs) have been fabricated by a multiple-exposure nanosphere lithography (MENSL) method using the self-assembled nanospheres as lens-mask patterns and the collimated laser beam as a multiple-exposing source. The arrays of the 2D pair-PCs exhibited variable lattice structures and shape the control of rotating angle (${\Theta}$), tilting angle (${\gamma}$) and the exposure conditions. In addition, the base period or filling factor of pair-PCs as well as their shapes could be changed by experimental conditions and nanosphere size. A 1.18-${\mu}m$-thick resist was spincoated on Si substrate and the multiple exposure was carried out at change of ${\gamma}$ and ${\Theta}$. Images of prepared 2D pair-PCs were observed by SEM. We believe that the MENSL method is a suitable useful tool to realize the pair-periodic arrays of large area.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.26 no.10
• /
• pp.1576-1583
• /
• 1989

In this paper, we describe real-time optical implementation of the Hopfield neural network model for two-dimensional associative memory by using commercial LCTV and Multifocus For real-time processing capability, we use LCTV as a memory mask and a input spatial light modulator. Inner product between input pattern and memory matrix is processed by the multifocus holographic lens. The output signal is then electrically thresholded fed back to the system input by 2-D CCD camera. From the good experimental results, the proposed system can be applied to pattern recognition and machine vision in future.

• Journal of the Korean Society for Precision Engineering
• /
• v.24 no.8 s.197
• /
• pp.138-143
• /
• 2007

Microstereolithography technology is similar to the conventional stereolithography process and enables to fabricate a complex 3D microstructure. This is divided into scanning and projection type according to aiming at precision and fabrication speed. The scanning MSL fabricates each layer using position control of laser spot on the resin surface, whereas the projection MSL fabricates one layer with one exposure using a mask. In the projection MSL, DMD used to generate dynamic pattern consists of $1024{\times}768$ micromirrors which have $13.68{\mu}m$ per side. The fabrication range and resolution are determined by the field of view of the DMD and the magnification of the projection lens. If using the projection lens with high power, very fine microstructures can be fabricated. In this paper, the projection MSL system adapted to a large surface for array-type fabrication is presented. This system covers the meso range, which is defined as the intermediate range between micro and macro, with a resolution of a few ${\mu}m$. The fabrication of array-type microstructures has been demonstrated to verify the performance of implemented system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.3
• /
• pp.227-231
• /
• 2013

Electrodeionization is a hybrid separation process of electrodialysis and ion exchange to produce high purity water under electric field. This article provides a fabrication result of hole patterned metal electrode for elecrodeionization system. The hole patterns have been fabricated by nanosphere lithography (NSL). The technique utilizes the self-assembled nanospheres as lens-mask patterns and collimated laser beam source. The hole patterns have a periodic array structure. The images of hole pattern on metal electrode prepared were observed by SEM. We believe that the periodic hole patterned metal electrode structure is a useful device applicable for metal mat electrode in electrodeionization system.

• Design & Manufacturing
• /
• v.14 no.3
• /
• pp.44-49
• /
• 2020

One of display trends today is development of high pixel density. To get high PPI, a small size of pixel must be developed. RGB pixel is arranged by evaporation process which determines pixel size. Normally, a fine metal mask (FMM; Invar alloy) has been used for evaporation process and it has advantages such as good strength, and low thermal expansion coefficient at low temperature. A FMM has been manufactured by chemical etching which has limitation to controlling the pattern shape and size. One of alternative method for patterning FMM is laser micromachining. Femtosecond laser is normally considered to improve those disadvantages for laser micromachining process due to such short pulse duration. In this paper, a femtosecond laser drilling for thickness of 16 ㎛ FMM is examined. Additionally, we introduce experimental results for controlling taper angle of hole by vibration module adapted in laser system. We used Ti:Sapphire based femtosecond laser with attenuating optics, co-axial illumination, vision system, 3-axis linear stage and vibration module. By controlling vibration amplitude, entrance and exit diameters are controllable. Using vibrating objective lens, we can control taper angle when femtosecond laser hole drilling by moving focusing point. The larger amplitude of vibration we control, the smaller taper angle will be carried out.

• The Bulletin of The Korean Astronomical Society
• /
• v.40 no.1
• /
• pp.53.2-53.2
• /
• 2015

Fiber Bragg gratings (FBGs) are the most compact and reliable method of suppressing atmospheric emission lines in the infrared for ground-based telescopes. It has been proved that real FBGs based filters were able to eliminate 63 bright sky lines with minimal interline losses in 2011 (GNOSIS). Inscribing FBGs on multi-core fibers offers advantages. Compared to arrays of individual SMFs, the multi-core fiber Bragg grating (MCFBG) is greatly reduced in size, resistant to damage, simple to fabricate, and easy to taper into a photonics lantern (PRAXIS). Multi-mode fibers should be used and the number of modes has to be large enough to capture a sufficient amount of light from the telescope. However, the fiber Bragg gratings can only be inscribed in the single-mode fiber. A photonic lantern bi-directionally converts multi-mode to single-mode. The number of cores in MCFBGs corresponds to the mode. For a writing system consisting of a single ultra-violet (UV) laser and phase mask, the standard writing method is insufficient to produce uniform MCFBGs due to the spatial variations of the field at each core within the fiber. Most significant technical challenges are consequences of the side-on illumination of the fiber. Firstly, the fiber cladding acts as a cylindrical lens, narrowing the incident beam as it passes through the air-cladding interface. Consequently, cores receive reduced or zero illumination, while the focusing induces variations in the power at those that are exposed. The second effect is the shadowing of the furthest cores by the cores nearest to the light source. Due to a higher refractive index of cores than the cladding, diffraction occurs at each core-cladding interface as well as cores absorb the light. As a result, any core that is located directly behind another in the beam path is underexposed or exposed to a distorted interference pattern from what phase mask originally generates. Technologies are discussed to overcome the problems and recent experimental results are presented as well as simulation results.