Sdudy Of Terahertz Zone Plate

The zone plate has a long history in optics. This concept at non-optical wavelengths is also applicable. In recent years, along with the development of terahertz technology, zone plates were developed in terahertz frequencies. The terahertz zone plate offers the advantages of simplicity of design and construction, low loss, low weight, and low cost. The zone plate with continuous phase propably becomes one of the important function devices in terahertz frequencies.First of all, this investigation addressed the design of zone plate with continuous phase for terahertz frequencies. The relation between the feature size and some important parameters of the zone plate was analyzed, including focal length, F number, incident frequency and material refractive index. Some factors that affect the zone plate's efficiency were also discussed. A series of typical parameters was presented for the zone plates, which are made of foamed polyethylene and high density polyethylene respectively.Secondly, diffraction fields of the zone plate with continuous phase and the phase-correcting Fresnel zone plate with uniform plane wave, spherical wave and gaussian beam incidence were analyzed and compared. The simulations of intensity distribution on the focal plane and the optic axis based on Rayleigh-Sommerfeld diffraction formula were completed by using Matlab. The results indicate that the zone plate with continuous phase has a better performance than the phase-correcting Fresnel zone plate. The effects of the focal length and diameter of the zone plate with continuous phase on the diffraction field were also discussed.Finally, materials and processing were discussed. The effects of the machining errors and approximation using inclined planes on the performance of the zone plate were discussed. The methods of testing were proposed, including testing of the surface shape and the performance. Possible application of the terahertz zone plate was studied as well, which focused on possibility of terahertz zone plates using as terahertz comb filters was focused on. The results indicate that the zone plate with continuous phase has a good performance for terahertz comb filter.