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研究(Research)

情報通信(IT)分野では、様々な材料、デバイス、システムが融合して高度な情報通信技術を実現しています。この様な中、未来の高性能光デバイスの実現に向けて、光学ポリマー(高分子)を応用した研究が世界中で活発に進められています。また、近年では自動運転技術のための高速情報処理技術への応用など新たな展開も広がっています。本研究室で光学的に高性能なポリマーを応用した光デバイスの研究を進めています。また、ポリマーのみならずシリコンや窒化シリコンなどの無機光学材料と融合したハイブリッド光学デバイスの研究展開も進めています。研究成果は、国内外の学会はもとより国際会議や国際的な専門論文誌へ数多く発表し、世界からも高い評価を受けています。



最新研究成果(Recent five)

駆動電圧0.9V、速度40GHzの高速ハイブリッドEOポリマー/シリコン光変調器

Hybrid EO plymer and silicon waveguide modulator, Vp=0.9V, 40GHz

We have demonstrated a low half-wavelength voltage of 0.9 V at the wavelength of 1.55 mm by using a Mach-Zehnder interference modulator. The measured modulation corresponded to an effective in-device EO coefficient of 165 pm/V. The 3 dB modulation bandwidth was measured to be 23 GHz. In addition, the high frequency sideband spectral measurement revealed that a linear response of the modulation index against the RF power was confirmed up to 40 GHz signal.


Optical Express 25, 768 (2017)

EOポリマークラッド層の酸化チタン光導波路変調器の高性能特性


EO polymer cladd TiO2 waveguide modulator
Organic electro-optic (EO) materials and their hybrid systems have received considerable attention for high-performance modulators.
We demonstrate the design and fabrication of an EO modulator with a low half-wave voltage (Vp) and a RF modulation response up to at least 10 GHz. An EO polymer-cladded titanium dioxide (TiO2) waveguide structure can be utilized to enlarge the confinement factor and thus enable a low Vp. The response of the modulator from 4 to 10 GHz has been measured, which shows a ?at frequency response up to 10 GHz and a potential for the application in several tens GHz.


Appl. Phys. Lett., 109, 173301 (2016)

熱安定性ポリノルボルネンの合成と光学特性


Polynorborne and optical properties
We have studied the ROMP of a well utilized monomer, N-cyclohexyl-exo-norbornene-5,6-dicarboximide (CyNDI), using four common initiators, Grubbs (G1, G2, HG1, and HG2) with differing ligands, thus effecting the rate and stereochemistry of the produced polymers. Of these initiators, only G1 was able to control the polymer molecular weight precisely, with a close correlation to calculated values. We have also demonstrated that when using G1, the refractive indices of the polymers increased as the Mw decreased in the range 1.5101 to 1.5394 at 633 nm from a Mw of 34,100 to 8,600.


European Polymer Journal 84, 89-99 (2016)

EOポリマー光導波変調器の高効率電場配向と熱安定性


EO polymer modulator, high poling efficiency and thermal stability
A titanium dioxide /EO polymer hybrid waveguide modulator was designed and fabricated. This modulator possessed a significant advantage for realizing high poling efficiency. The in-device EO coefficient was measured to be 100 pm/V, which was 32% higher than that of the thin polymer film. As a result, the phase modulator displayed a
VpL figure of merit of 3.5 V/cm at 1550 nm. Temporal stability test of the modulator at 85oC indicated only 8% change of Vp over 500 hours.


Optical Express 24, 19020 (2016).

熱安定化ハイブリッドシリコン/EOポリマーリング共振器変調器


Thermally stable hybrid silicon and EO polymer ring resonator
In this work, we have demonstrated a hybrid silicon / polymer ring resonator electro-optic (EO) modulator with a temperature independent modulation. The waveguide consisted of an ultra-thin silicon core with an EO polymer cladding. With a radius of 60
μm, the ring exhibited a 9.7 dB extinction depth and a Q value of 1.25×10^4. After poling of the EO polymer, the ring resonator functioned well as an EO modulator and operated in a stable manner between 25-55°C.


ACS Photonics 3, 780-783 (2016).