POLARIZING REFLECTION GRATING BEAMSPLITTER FOR THE 10.6-MU-M WAVELENGTH

A polarizing grating beamsplitter working in reflection at the 10.6-mum wavelength is presented. The grating was designed using rigorous diffraction theory. The incident TM-polarized light is not diffracted but reflected as the zero order, and the TE-polarized light is mainly diffracted into the +1 and -1 diffraction orders. The grating is a surface relief with a metal coating. It consists of V-grooves and is fabricated in silicon using photolithography and a combination of dry and wet chemical etching. The measured diffraction efficiencies agree with the theoretical predictions. The sum of the measured diffraction efficiencies of the +1 and the -1 orders is 90% for TE polarization and 6% for TM polarization. If the grating is in a conical mount, it can be used as a beam attenuator or a three-way beamsplitter.