For decades optical lithography has continually been extended past the conceived limitations of the technology. By optimizing photoresist performance and stepper settings it is possible to image features smaller then the wavelength of light being used to image. This ability allows structures to be designed such that the optical properties of the material change from what would occur at larger scales. One such structure is the wire grid array consisting of parallel metal lines on a quartz substrate. A wire grid array with a period smaller then the wavelength of incident radiation acts as a polarizer. The Incident field perpendicular to the metal wires, transverse magnetic (TM or P) is maximized. The incident field parallel to the metal wires, transverse electric (TE or S), is minimized. A polarization filter implementing a wire grid array is demonstrated using i-line lithography.
"Design and Fabrication of Polarization Filter Implementing a Wire Grid Array,"
Journal of the Microelectronic Engineering Conference: Vol. 12
, Article 1.
Available at: http://scholarworks.rit.edu/ritamec/vol12/iss1/1