Nobuo Kushibiki

Silicone polymers for optical films and devices

Silicones are among the most suitable materials for optical telecommunication devices due to their tolerance to high optical flux and their thermo-mechanical and environmental stability; they also have excellent processability. This work focuses on utilizing silicon-based branched resins and linear polymers for optical waveguides and switches where both refractive index and thermo-optic coefficient need to be controlled to the requirements of specific applications. Materials were synthesized with high optical transmission bands between 1.3 and 1.6 μm by varying the amount of aliphatic and aromatic C-H in the material. At the same time, the ratio of methyl to phenyl groups also controls the refractive index in the range of nD = 1.4 ... 1.6 precisely enough that both core and cladding components (Δn < 0.5%) can be obtained. Films of 5 to 20 μm thickness prepared on silicon substrates by spin-coating from solution were evaluated by measuring refractive index, thermo-optic coefficient, optical loss, and film uniformity both before and after exposure to high temperature and humidity. These films can be patterned through a number of techniques to form the required features. The resinous materials show very low birefringence and excellent resistance to heat and moisture.

Light emission properties of poly(diphenylsilylenemethylene) and poly(diphenylsiloxane) by UV laser irradiation

Abstract Unique light emission phenomena of poly(diphenylsilylenemethylene) (PDPhSM) and poly(diphenylsiloxane) (PDPhSO) by UV laser irradiation were observed. When PDPhSM films were irradiated with an excimer laser (KrF, 248 nm), light emission, whose spectra were broad ranging from 300–500 nm and exhibiting a large peak at 340 nm, was observed. Blue-green light emission was observed for several seconds, after the laser light was turned off. Furthermore, the emission spectra were found to change with a number of laser shots irradiated. The emission peak at 340 nm decreased rapidly, while the emission in the range from 400–600 nm increased gradually as the sample was repeatedly irradiated with the laser. A similar characteristic light emission was also observed with PDPhSO films.

FASTER GRATING BUILDUP CHARACTERISTICS IN LOW SILANOL-CONTAINING POLYSILANE-BASED PHOTOREFRACTIVE POLYMER

The effect of silanol content on the grating buildup dynamics was examined by preparing two different lots of polymethylphenylsilane (PMPS). While the high silanol-containing PMPS showed very sluggish grating formation time, the lower silanol-containing PMPS exhibited very rapid grating formation in a diffraction efficiency measurement. The diffraction efficiency, on the other hand, was found to be unaffected. The results suggest that the silanol is acting as hole trap and a reduction of its content is a key to improving the response characteristics of polysilane-based photoconducting electro-optic polymer composite for photorefractive applications.

Free-standing films based on silicone resins

We report here the preparation of transparent, flexible films from silicone resins by solvent casting techniques. The films exhibit no birefringence, higher than 90% transparency between 350 to 1700 nm and average surface roughness below 1 nm. Thermal analysis shows that the films are stable at temperatures greater than 200 °C (depending upon the starting resin composition). The films are suitable substrates for deposition of various coatings including indium tin oxide (ITO). Transparent conducting ITO electrodes were prepared with ion plating and RF sputtering methods and characterized by microscopy, XPS, absorption spectroscopy and electrical conductivity measurements. Potential applications for silicone resin films exist in the market areas of displays, electronics and energy.