基于双层金属光栅的高消光比高透过率太赫兹偏振器

Terahertz Polarizer with High Extinction Ratio and High Transmittance Based on Bilayer Metal Grating

本文设计了一种基于双层金属亚波长光栅的太赫兹偏振器,其可以实现高透过率和良好消光比的特性.该偏振器是通过微加工技术在薄石英衬底的上下表面上制备而成的.实验和模拟结果均表明,双层金属光栅具有与单层金属光栅相近的透过率、更高的偏振度和更高的消光比.在0.3~2.0 THz的频率范围内,测量的透过率在83.4%到62.7%之间,偏振度大于99.7%,消光比大于29 dB.此外,设计的两种双层金属光栅偏振器件成功地应用于太赫兹时域光谱(TeraHertz Time Domain Spectroscopy,THz-TDS)系统中,获得了超过96.2%的偏振度和超过17.1 dB的消光比.通过调整金属亚波长光栅的参数(例如间距、线宽和金属膜厚度),可以进一步提高透过率、偏振度和消光比等特性.

A terahertz polarizer based on bilayer metal subwavelength-grating is designed to achieve high transmis⁃sion and good extinction ratio.The polarizer is fabricated on the upper and lower surfaces of thin quartz substrate by mi⁃cro-fabrication technique.Both experimental and simulation results show that the bilayer metal grating has similar trans⁃mittance,higher degree of polarization and extinction ratio than the single-layer metal grating.Measured transmittance is between 83.4%and 62.7%in the frequency range of 0.3~2.0 THz,and the degree of polarization and extinction ratio is more than 99.7%and more than 29 dB,respectively.In addition,the two designed bilayer metal gratings are success⁃fully used in the terahertz time-domain spectroscopy(THz-TDS)system,and the degree of polarization of more than 96.2%and the extinction ratio of more than 17.1 dB are obtained.The transmittance,degree of polarization and extinction ratio can be improved by further tuning the parameters(such as the pitch,line width,and metal film thickness)of the metal subwavelength-grating.