Experimental study on polarization lens formed by asymmetrical metallic hole array

A polarization bifocal lens based on the polarization effect caused by asymmetrical hole arrays had been designed, fabricated, and characterized experimentally. By considering the fact that the skin depth of an infrared electromagnetic field inside metal is much shorter than the incident wavelength, a polarization bifocal lens composed of high deep-width ratio metallic holes was realized by using a gold-coated silicon structure to replace the one directly formed on a thick metal film. An infrared optical experiment setup is built based on the secondary imagery method for characterizing the focal length of the designed bifocal lens. The measured focal lengths of the fabricated bifocal lens coincide well with the designed values, which proves the validity for realizing the polarization elements with the proposed structure and the feasibility of the fabrication process.