All Optical Switching and Bistability Device using Surface Plasmon Resonance

本工作的目的是建立一种利用三阶非线性光学效应和表面等离子体激元共振（SPR）增强来制作全光开关器件的方法。我们的主要工作是：（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）利用非线性光学评价光学质量的探测方法，（4）开关器件的制备和光学性能的评价，（5）响应的计算机模拟。作为材料，我们使用了尺寸为100-120微米的聚二乙炔（PDA）纳米颗粒。我们使用聚乙烯醇（PVA）作为PDA纳米颗粒的基质。使用PDA在PVA基质中的溶液通过旋涂方法制造膜。通过这种方法获得了控制良好的膜。我们还发展了一种利用三阶非线性光学效应之一的三次谐波产生，通过分析三次谐波产生的Maker条纹来评价其光学质量的探测方法。根据这些结果，我们制作了基于SPR的所有光学器件。观察到的开关特性，但他们比我们预期的计算机模拟弱。这是因为纳米颗粒的存在使得光的相干性降低了30%以下，并且表面等离子体激元的激发较弱。由于我们还获得了直径为40 nm的纳米颗粒提供了良好的相干性，因此使用直径为40 nm的PDA纳米颗粒的开关器件将具有全光开关的能力。这些结果表明，π共轭聚合物，如PDA将是有前途的材料，高速光学器件。

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.