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表面等离子光波导组成的线性耦合器
摘要基于表面等离子极化的表面等离子光波导提供了一种新的导波机制,可以在金属表面上以表面等离子极化波的形式导引光。表面等离子光波导的横向尺度为亚波长量级,没有传统光波导或光子晶体光波导中存在的衍射极限,满足了光子器件小型化和光集成芯片高密度化的要求,同时也为电路和光路的一体化提供了可能。
在表面等离子光波导中,电场高度集中于金属和介质的界面上,能量密度非常大,所以为线性效应的利用提供了有利条件,也为亚波长线性器件的构成提供了可能。更重要的是,基于线性表面等离子光学的有源光器件将实现允许用光来控制光,从而为实现全光集成光路提供理论依据及思路。
本文运用耦合模理论分析了表面等离子光波导组成的线性耦合器的输出特性,发现金属带构成的耦合器中两波导可以实现周期性的能量交换。针对金属带自身特点提出了一种能够明显减小其尺寸的直接耦合器结构。直接耦合器的耦合长度随工作波长变化而变化,基于此原理采用金属带构造了1330nm/1550nm 波分复用及解复用器。
关键词等离子光波导;线性耦合器。
ABSTRACT
Surface plasmon optical waveguides provide a new mechanism of guiding waves. SPPs are ic waves that exist on the surface of metals. The lateral dimension of surface plasmon optical waveguides is subwavelength scale. Not like the convensional optical waveguides and photonic crystal waveguides, the dimension of these waveguides are not limited by diffraction limit. They meet the need of the miniaturization and high-density integration of optical circuits and make it possible to integrate plasmonic, electronic, and conventional dielectric photonic devices on the same chip.
In surface plasmon optical waveguides, the electric field focuses on the dielectric-metal interface with superior high energy density, which provides favorable conditions for using of nonlinear effects and possibility of constructing of subwavelength nonlinear devices. Mostimportantly, active nanophotonic elements based on nonlinear surface plasmon optics allowing control of light with light are imperative for implementation of all-optical integrated circuits.
This article also analyzes output characteristics of directional couplers based-on surface plasmon optical waveguides using coupled-mode theory. It is found that two metal stripes can periodically exchange energy, while the periodical exchange of energy cannot be realized in the V-groove and the triangular wedge because the high concentration of energy; and
complete energy transfer happen only when two waveguide is very nearly. A new directional coupler is presented, w