Fourier Gratings as Submillimeter Beam Splitters

Urs U. Graf and Stefan Heyminck

Abstract:

Over the past years a number of groups have developed phase gratings as local oscillator beam multiplexers for array receivers in the submillimeter wavelength domain. The most popular type of grating is the Dammann grating, a simple and versatile binary phase grating.

We introduce a new type of grating, the Fourier grating, which, in contrast to the binary structure of Dammann gratings uses a smooth grating structure. Due to the lack of sharp edges these gratings can be manufactured with high precision as reflection gratings even for two-dimensional dispersion.

Fourier gratings are designed using a simple optimization procedure, which only involves a small number of parameters. Their diffraction efficiency is very high. We have produced a number of gratings and tested them at a frequency of 490 GHz, verifying the theoretical results.