All Optical Switching and Bistability Device using Surface Plasmon Resonance

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Purpose of this work is to establish the way to make all optical switching devices using third-order nonlinear optical effect with an enhancement of surface plasmon resonance (SPR). What we have done is followings (1) Investigation of excitation of SPR using the attenuated total reflection geometry, (2) Fabrication of films of nonlinear optical materials with good optical quality, (3) Probing method to evaluate the optical quality using nonlinear optics, (4) Fabrication of switching devices and evaluation of the optical properties, (5) Computer simulation of the response. As materials, we used nanoparticle of polydiacetylene (PDA) with a dimension of 100-120 microns. We used polyvinylalchohol (PVA) as a matrix for the PDA nanoparticles. The films were fabricated by the spin coating method using a solution of PDA in a PVA matrix. Nicely controlled film was obtained by this method. We also developed a probing method to evaluate the optical quality using third harmonic generation, which is one of the third-order nonlinear optical effects, by the analysis of the Maker fringes of THG. From these results, we fabricated all optical devices based on SPR. The switching properties were observed but they were weaker than we expected from the computer simulation. This is because that the coherence of the light was reduced less than 30% because of the nanoparticles and the excitation of surface plasmons were weak. Since we also obtained that the nanoparticles with a diameter of 40 nm provides good coherence, the switching devices using the PDA nanoparticles with a diameter of 40 nm will have the capability for the all optical switching. These results suggest that pi-conjugated polymers such as PDA will be promising materials for high speed optical devices.