Eliminating ± 1st orders by double-groove microstructure for three-branch electromagnetic wave splitting

We investigated a three-channel reflective grating beam splitter with double-groove which eliminated ± 1st orders under TE and TM polarization. The grating has a polarization-dependent structure with different ridge thicknesses under TE and TM polarizations. Inhibitions of ± 1st orders are rarely reported from the previous work. The diffraction efficiency of the 0th order and ± 2nd orders for TE polarization orders can reach 32.7% and 33.3%, respectively. And the diffraction efficiency of 0th order and ± 2nd orders for TM polarization can reach 32.9% and 31.9%, respectively. It indicates that the uniformity of diffraction efficiency under the two polarizations also reaches more than 95%. The excellent bandwidth and tolerance make this grating suitable for a wide range of applications in the optical field. Compared conventional three-channel splitting, inhibitions of ± 1st orders are presented by double-groove microstructure.