• Proceedings of the Optical Society of Korea Conference
• /
• 2007.07a
• /
• pp.303-304
• /
• 2007

• Journal of Photoscience
• /
• v.9 no.1
• /
• pp.23-28
• /
• 2002

In order to obtain thermal-stable, low birefringent, and low optical loss waveguiding materials, we synthesized several fluorinated poly (maleimide-co-glycidylmethacrylate)s using a pentafluorophenylmaleimide (PEM) and two kinds of methacrylate derivatives as comonomers and glycidylmethacrylate as a crosslinker. One comonomer is a linear fluorinated methacrylate (HFBM) and another is a bulky norbornane-derived methacrylate (NMMA). These copolymers could be self-crosslinked by heating due to epoxy groups of glycidylmethacrylates. As a maleimide contents increased to 50 mol%, these copolymers showed high decomposition temperatures of above 300$^{\circ}C$. The refractive index could be precisely controlled by the variation of PFM/HFBA or PFM/NMMA feed ratio in the range of 1.410∼1.508 at 643 nm. The copolymers had very low birefringence in the range of 1∼5${\times}$10$\^$-4/.

• Polymer(Korea)
• /
• v.26 no.2
• /
• pp.253-259
• /
• 2002

The objective of this study is to obtain thermally stable and low optical loss polymers for optical waveguiding materials. The crosslinkable poly (maleimide-co-methacrylate)s were synthesized using a pentafluorophenylmaleimide (an optical loss reducer), two methacrylate derivatives (refractive index controllers), and a glycidylmethacrylate (a crosslinker). These copolymers exhibited good thermal stability and could be thermally crosslinked by heat treatment. The refractive indexes of the copolymers could be precisely controlled by the variation of comonomer feed ratio, which was in the range of 1.45 ~ 1.49. These copolymers had very low birefringence of $6{ imes}10^{-4}$ ~ $1{ imes}10^{-4}$. These copolymers were crosslinked by contact printing and then developed by wet etching to obtain high quality waveguide pattern.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.19 no.5
• /
• pp.5-11
• /
• 1982

The dielectric slab waveguide is fabricated on the slide glass or oxidized silicon wafer, by spin coating polyurethane, epoxy or photoresist, and the phenomenon of dielectric waveguiding is oboerved. Using the fact that the refractive index of K.P.R. is larger than that of polyurethane, thin film prism with two layered structure is fabricated, and the refraction of light is observed.

• Journal of the Optical Society of Korea
• /
• v.3 no.1
• /
• pp.23-26
• /
• 1999

A simple technique to measure electro-optic coefficients has been developed. It is based on rotating analyzer polarimetry. With a coaxial configuration of the optically active polarizing devices, the synchronously digitized signals are Fourier analyzed to quantitatively determine the elliptical polarization of light and, hence, the electric field induced birefringence. This technique has the advantage that it does not require waveguiding, and since it is improved from the crossed polarizer method it measures the phase retardation directly. It has been applied for the precise determination of electro-optic coefficients of uniaxial LiNbO3 single crystals. The excellent agreeement with reported values confirms its usefulness toward accurate characterization of electro-optic coefficients of unknown specimens.

• The Korean Journal of Ceramics
• /
• v.1 no.4
• /
• pp.191-196
• /
• 1995

Using sol-gel processing method, thin films of lathanum modified lead titanate(PLT) on Corning 7059 glass were prepared. A differential thermal analysis (DTA/TG) curve of gel powder and infrared spectra (FT-IR) of the films were measured to estimate residual organices in them. The heat-treated films were characterized by X-ray diffraction(XRD). Microstructures of the films were observed by a scanning electron microscope (SEM). Optical properties of the films were determined by a UV-VIS spectrophotometer. The waveguiding properties and optical attenuation were measured with the end coupling method and the cut back method. Effects of the drying conditions on the transmittance and the propagation loss of the films were investigated. Experimemtal results showed that the content of residual organics in the film decreased as the drying temperature of the film increased. As the La content of the film increased, the grain size decreased and the transmittance increased. The transmittances of the films increased with the increasing of the drying temperature. The propagation losses in the film decreased as the drying temperature increased.

• Journal of the Korean Ceramic Society
• /
• v.42 no.3 s.274
• /
• pp.178-181
• /
• 2005

Silicon oxynitride (SiON) layers deposited upon a $SiO_2/Si$ buffer layer placed upon silicon wafers have been obtained by using PECVD from $SiH_4,\;N_2O$, and $N_2$. It can be seen that the refractive index, measured by using a prism coupler, for the SiON films can be varied between 1.4480 and 1.4958 at a wavelength of 1552 nm by changing the process parameters. Optical planar waveguides with a thickness of $6{\mu}m$ and a refractive index contrast ($\Delta$n) of $0.36\% have been deposited. Also, etching experiments were performed using ICP dry etching equipment on thick SiON films grown onto Si substrates covered by a thick $SiO_2$ buffer layer. A polarization maintaining single-mode fiber was used for the input and a microscope objective for the output at $1.55{\mu}m$. As a result, a low index contrast SiON based waveguide is fabricated with easily adjustable refractive index of core layer. It illustrates that the output intensity mode is a waveguiding single-mode.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2006.08a
• /
• pp.421-421
• /
• 2006

The light and energy-efficiency of classical liquid crystal displays is notoriously poor due to the use of absorption-based linear polarisers and colour filters. For instance, the light efficiency of PVAL polarisers is typically between 40 and 45 % and the colour filters have a typical efficiency below 35 % which results in a total light and energy-efficiency of the display below 10 %. In the past, a variety of polarizers were developed with an enhanced efficiency in generating linearly polarized light. Typically, these polarizers are based on the polarisationselective reflection, scattering or refraction of light i.e. one polarisation direction of light is directly transmitted to the LCD/viewer and the other polarization direction of light is depolarised and recycled which results in a typical efficiency for generating linearly polarized light of 70-85 %. Also, special colour filters have been proposed based on chiral-nematic reactive mesogens which increase the efficiency of generating colour. Despite the enormous progress in this field, a need persists for improved methods for generating polarized light and colour based on low cost optical components with a high efficiency. Here, the use of holographic phase gratings is reported for the generation of polarized light and colour. The phase grating are recorded in a photopolymer which is coated onto a backor frontlight for LCDs. Typically the recording is performed in the transmisson mode or in the waveguiding mode and slanted phase gratings are generated with their refractive index modulation at an angle between 20o and 45o with the normal of the substrate. It is shown that phase gratings with a high refractive index modulation and a high efficiency can be generated by a proper selection of the photopolymer and illumination conditions. These phase gratings coupleout linearly polarized light with a high contrast (> 100) and the light is directed directly to the LCD/viewer without the need for redirection foils. Dependent on the type of phase grating, the different colours are coupled-out at a slightly different angle which potentially increases the efficiency of classical colour filters. Moreover, the phase gratings are completely transparent in direct view which opens the possibility to use them in frontlights for LCDs. Holographic polarization gratings posses a periodic pattern in the polarization state of light (and not in the intensity of light). A periodic pattern in the polarization direction of linearly polarized light is obtained upon interference of two circularly polarized laser beams. In the second part of the lecture, it is shown that these periodic polarization patterns can be recorded in a linear photo-polymerizable polymer (LPP) and that such an alignment layer induces a period rotation in the director of (reactive and non-reactive) liquid crystals. By a proper design, optical components can be produced with only first order diffraction and with a very high efficiency (>0.98). It is shown that these diffraction gratings are potentially useful in projection displays with a high brightness and energy efficiency