A high-diffraction-efficiency subwavelength silica Dammann grating

In this paper, a large scale and highly efficient 1 × 9 Dammann beam splitter operating in 1.064 μm wavelength for TE polarization is designed and fabricated under normal incidence. This element consisting of a triple-groove fused silica grating layer is designed using the inverse mathematical method and rigorous vector diffraction theory. The beam splitter is fabricated by using the self-developed blue light laser writing system and dry etching technique. The fabricated beam splitter presents excellent beam splitter ability for TE polarization light with the average diffraction efficiencies is more than 85% at 1.064 μm wavelength (96.4% in theory), which is over 20% higher than the traditional one.