数值模拟二维间隙表面等离子波导传输特性

利用表面等离子激元的新颖特性,设计了二维间隙表面等离子波导.以这种结构为基础通过变形和组合形成90°直角弯曲波导、T型光功率分配器和光开光,采用时域有限差分法研究了它们的传输特性.结果表明:不同于介质光波导的弯曲损耗来自于辐射泄漏,90°直角弯曲间隙表面等离子波导的能量损耗主要来自于金属中的欧姆热损耗.在间隙达到40 nm以上后,当直行段的长度适当时,弯曲段的透射率较相同长度的直波导的透射率要大.T型光功率分配器在两输出波导的间隙宽度比达到0.6及以上时,不同于传统介质波导的分光原则,能量主要沿等效折射率较小的输出臂流出.当两输入光的相位反相时,T型光开关处于输出截止的状态,当两输入光的相位同相时,T型光开关处于输出导通的状态.所有波导间隙均小于衍射极限,实现了超衍射极限传播,可用于未来了超大规模集成光路中.

Numerical Simulation of Transmission Characters of Two-dimensional Gap Plasmonic Waveguide

Two-dimensional gap plasmonic waveguide employing surface plasmon polaritons is proposed. Transmission characters of 90 degrees sharp bend waveguide, T-shaped splitter and switch based on gap plasmonic waveguide are numerical simulated with finite-difference time-domain method. It is shown that the energy loss of 90 degrees sharp bend waveguide is ohmic losses which are different to radiation losses of dielectric optical waveguide. When the gap width is larger than 40 nm, the transmission of bend waveguide is larger than straight waveguide with the same length. In the T-shaped splitter, when the gap width ratio of two output waveguides is larger than 0.6, the output energy is mainly assigned to the output waveguide which effective index is smaller. The result is different from dielectric optical splitter. The T-shaped switch is off with two input light out of phase and is on with two input light in phase. The plasmonic modes in the above devices beyond the diffraction limit and can be employed in super-large-scale optical integrated circuit.