Modeling the mid-infrared thermal radiative properties of silicon complex gratings

A finite-difference time-domain numerical scheme was used to model the infrared radiative properties of heavily doped silicon simple and complex gratings. High absorptance from heavily doped silicon for the transverse magnetic wave incidence can be achieved with one-dimensional periodic gratings. For simple binary gratings, the associated absorptance peak is narrowband. The drawback can be remedied by using complex gratings. The spectral absorptance displays a peak with a much bigger full-width-at-half-maximum FWHM . The broadband absorptance peak can be attributed to the excitation of surface plasmon polaritons based on the electromagnetic fields and Poynting vectors plots. It demonstrates that the complex gratings may significantly enhance the performance of infrared detectors.