Study On THZ Narrow-Band Filters Based On Cascade Double FP Cavities

Narrow-band filters mainly based on liquid crystals or Fabry-Perot cavities are key components to realize narrow line width THz wave output and measurement. For large power system, narrow-band filters based on liquid crystals have the problem of low damage threshold. But FP cavity filters are often used in large power system. Currently, materials such as silica, metal, silicon, germanium with high damage threshold can be used for the fabrication of FP cavity filters. Multiple FP cavities cascaded are needed to get narrow line width and wide spectrum of free path. In this thesis, two kinds of THz narrow-band filters based on cascade double FP cavities are studied. The main works are as follows.Firstly, THz narrow-band filters are designed with reflectors based on metal grids on intrinsic silicon substrates. The structure parameters are optimized by simulation. Then metal grid reflectors are fabricated by the micro-nano manufacturing process and measured. Results show that metal grids meet the requirements for reflectors of cascade double FP cavities. Although the THz reflectivity of the metal grid structure can be changed by the structure parameters, it is inconvenient to tune.Secondly, THz narrow-band filters are designed with reflectors of thin silicon wafers. Then the thickness of the intrinsic silicon wafer is designed carefully. Thin silicon wafers are made by anisotropic etching. According to the FP effect measured, the thickness is calculated accurately. When the thickness is 17.9 ?m or 30 ?m, the change of the thickness is less than 0.1 ?m in the area of 0.5mm×0.5mm. Therefore, silicon wafers can be used as broadband reflectors of FP cavities.