All Optical Switching and Bistability Device using Surface Plasmon Resonance

这项工作的目的是建立一种方法，使所有的光开关器件都利用三阶非线性光学效应，并增强表面等离子体共振(SPR)。我们所做的工作如下：(1)利用衰减全反射几何结构研究SPR的激发；(2)制备具有良好光学质量的非线性光学材料薄膜；(3)利用非线性光学来评价光学质量的探测法；(4)开关器件的制作和光学性能的评价；(5)响应的计算机模拟。作为材料，我们使用了尺寸为100-120微米的纳米聚二乙炔(PDA)。我们使用聚乙烯醇(PVA)作为PDA纳米颗粒的基质。用PDA溶液在PVA基质中旋涂的方法制备了薄膜。用这种方法可以得到控制良好的薄膜。通过对三倍频Maker条纹的分析，提出了利用三阶非线性光学效应中的三次谐波来评价光学质量的探测方法。根据这些结果，我们制作了所有基于表面等离子体共振的光学器件。观察到了开关特性，但它们比我们从计算机模拟中预期的要弱。这是因为纳米粒子和表面等离子体激发较弱，使光的相干性降低了不到30%。由于我们还得到了直径为40 nm的纳米粒子具有良好的相干性，因此使用直径为40 nm的PDA纳米粒子制作的开关器件将具有全光开关的能力。这些结果表明，聚酰亚胺等共轭聚合物有望成为高速光学器件的理想材料。

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.