Regular papers

Optical and THz Galois diffusers

¹ Physics Department, Integrated Optoelectronics and Microoptics Research Group, Kaiserslautern University of Technology, P.O. Box 3049, 67653 Kaiserslautern, Germany
² Nano Structuring Center, Research Center OPTIMAS, Kaiserslautern University of Technology, P.O. Box 3049, 67653 Kaiserslautern, Germany

^* fouckhar@physik.uni-kl.de

Received: 30 November 2012
Revised: 24 January 2013

Abstract

Binary surface reliefs with sub-wavelength features making up a pseudorandom pattern based on mathematical Galois fields GF(p^m) [1, 2] can scatter incoming waves into a large number of diffraction maxima within a huge solid angle. A one-dimensional (1D) Galois number sequence can be folded into a two-dimensional (2D) array by the sino-representation [2]. This concept was been verified for acoustic waves a long time ago [3, 4] and is investigated here for visible light and THz waves. Our Galois diffusers are designed as reflection reliefs and realised by electron beam lithography for the optical regime and UV photolithography for the THz regime. Our results show that optical and THz Galois surfaces are excellent diffusers for electromagnetic waves; they distribute the reflected intensity evenly over a large number of maxima nearly within the entire half solid angle in the backward direction.