Polarization-independent total-internal-reflection grism with 95% diffraction efficiency for wavelength selective switches

A polarization-independent reflective grism consists of a polarization-independent total-internal-reflection grating and a prism. It can offer high line density, wide bandwidth and linear dispersion, promising potential application to next-generation wavelength selective switches. We designed and fabricated a grism of a line density of 1710 lines/mm. The average diffraction efficiency for TE and TM polarizations over the C-band (1523-1575 nm) is 95.14%.