基于光子晶体马赫.曾德尔干涉仪的太赫兹开关及强度调制器

Photonic-crystal-waveguide based Mach-Zehnder interferometer for terahertz switch and modulator

通过对二维正方晶格光子晶体线缺陷模色散曲线慢光特性的研究,利用外电场对液晶分予取向的调控作用,在填充液晶的正方晶格波导的马赫-曾德尔干涉仪结构中实现了开关和强度调制等功能.利用平面波展开法计算了光子晶体波导的线缺陷模,分析了液晶折射率的变化对缺陷模的影响.计算表明,液晶折射率仅改变了0.1,线缺陷模有效折射率改变达0.168,该特性可以更为有效地实现对相位的控制,进而实现高消光比开关和强度调制功能,这种高效的相位调节器件在集成光系统中将有很好的应用前景.

We propose a novel tunable photonic crystal（PC） waveguide Mach-Zehnder interferometer（MZI） based on nematic liquid crystals （LCs） 5CB and investigate its interference properties numerically by using the finite-difference time-domain method.We can change the refractive index of LC by rotating the directors of the LC molecules.The line defect modes of the PC waveguide with different liquid crystal refractive indices are analyzed by using the plane wave expansion method.Owing to the slow group velocity region of the line defect mode,when the index of 5CB changes from 1.53 to 1.63,the variation of the effective index of the line defect mode arrives at 0.168.This property helps to significantly control the phase of light propagation in a PC waveguide MZI.The novel interferometer can be used as either an optically controlled on-off switch or an amplitude modulator in optical circuits.