Zone plate designs for terahertz frequencies

James C. Wiltse

doi:10.1117/12.602657

18 May 2005 Zone plate designs for terahertz frequencies (Invited Paper)

James C. Wiltse

Proceedings Volume 5790, Terahertz for Military and Security Applications III; (2005) https://doi.org/10.1117/12.602657
Event: Defense and Security, 2005, Orlando, Florida, United States

Abstract

The phase-correcting Fresnel zone plate provides lens-like focusing and imaging of electromagnetic waves by means of diffraction instead of refraction, often referred to as diffraction optics. The zone plate has seen extensive investigation and use at microwave and millimeter-wave frequencies, and recently has been applied in the terahertz region. These cases have dealt principally with large-angle designs, where the focal length (F) and diameter (D) are comparable (F/D = 0.3 to 2.5), unlike the typical optical examples. The planar zone plate, in particular, offers the advantages of simplicity of design and construction, low loss, low weight, and low cost, while giving performance similar to that of a refractive lens. As one goes to terahertz frequencies, ease of construction becomes more difficult. The attenuation in conventional low-loss materials increases at higher frequencies, and dimensional tolerances become smaller, making fabrication more difficult. Although earlier designs employing polystyrene have been built and tested at frequencies up to 280 GHz, higher frequency designs are simpler to fabricate and have lower loss if low dielectric constant materials are used. This investigation addressed designs for terahertz frequencies. The optimization of the zone plate has also been examined, and improvement has been found for radial compression, where the radii of the zone boundaries are slightly shortened.

Citation Download Citation

James C. Wiltse "Zone plate designs for terahertz frequencies (Invited Paper)", Proc. SPIE 5790, Terahertz for Military and Security Applications III, (18 May 2005); https://doi.org/10.1117/12.602657

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