Nonlinear Optical Device using Bacteriorhodopsin and Surface Plasmon Resonance and Its Applications

利用表面等离子体激元共振技术制作了一种非线性光学器件。在该装置中，细菌视紫红质膜，这是通过离心制备，沉积在薄银膜涂层棱镜表面。反射率与入射角的关系曲线中所示的共振凹陷随着入射光束强度的增加而向低角度移动。测得的非线性折射率为n_2=-0.054cm^2/W。然而，由于细菌视紫红质薄膜随时间的推移而收缩并被去除，因此该器件是不稳定的。为了解决这个问题，开发了使用泄漏模式光波导的替代装置，其中染料掺杂的聚合物膜用作非线性波导层。在这种器件中，波导中的场大于表面等离子体共振的场。在实验中，使用氩离子激光束测量了以双（4-二甲氨基-二硫代苯偶酰）镍掺杂的PMMA薄膜作为波导层的器件的反射率与入射角的关系。实验中观察到了几mW的谐振角位移和几十mW的光学双稳，但由于热效应，波导层在高强度下会受到损伤。对于更高的场增强，考虑了在波导上沉积小的胶体金颗粒。数值计算证实了粒子和波导之间的场被大大增强。本文介绍了分析光束在非线性光学介质中传输的数值方法，即非线性光学介质中的传输. G.细菌视紫红质膜，使用光束传播方法也被开发。用这种方法计算的结果与实验结果非常吻合。

A nonlinear optical device using surface plasmon resonance was fabricated. In the device a bacteriorhodopsin film, which was prepared by a centrifuge, was deposited on a thin-silver-film coated prism surface. The resonance dip shown in the reflectance versus the angle of incidence shifted toward lower angle as the intensity of the incident beam increased. The obtained nonlinear index of refraction was n_2=-0.054cm^2/W.However, the device is unstable because the bacteriorhodopsin film shrinks and is removed with time. To solve this problem an alternative device using a leaky-mode optical waveguide, in which a dye-doped polymer film was used as a nonlinear waveguide layer, was developed. In this device the field in the waveguide is larger than that by the surface plasmon resonance. In the experiments the reflectance versus the angle of incidence was measured with argon-ion laser beam for a device using bis (4-dimethylamino-dithiobenzil) nickel doped PMMA film as the waveguide layer. The resonance angle shifted for a few mW and optical bistability was observed for a few ten mW.However, the waveguide layer is damaged for the high intensity due to a thermal effect. For the higher field enhancement the deposition of small colloidal gold particles on the waveguide was considered. It was numerically confirmed that the field between the particles and the waveguide was much enhanced. The numerical method analyzing the propagation of beams in nonlinear optical media, e. g. bacterio-rhodopsin film, using the beam propagation method was also developed. The results using this method agreed very much with the experimental ones.