Silicon Diffractive Optical Elements for High-Power Monochromatic Terahertz Radiation

摘要

This paper presents a fabrication technique and results of studies of silicon binary diffractive optical elements (DOEs): a diffractive lens and a 1 : 2 diffractive beam splitter with an aperture diameter of 30 mm for the terahertz spectral range. The elements were fabricated in two versions: with and without an antireflection coating of parylene C. The DOE characteristics were investigated in the beam of the Novosibirsk free electron laser at a wavelength of 141 μm. The results are given of a study of the radiation resistance of the coating, which remained intact upon exposure to an average radiation power density of 4 kW/cm~2; the peak power in a 100 ps pulse was almost 8 MW/cm~2. Experimental estimates of the diffraction efficiency of the elements coated with the antireflection coating are in good agreement with theoretical estimates.