Broadband Absorption in Patterned Metal/Weakly-Absorbing-Spacer/Metal with Graded Photonic Super-Crystal

It is challenging to realize the complete broadband absorption of near-infrared in thin optical devices. In this paper, we studied high light two devices: a stack Au-pattern/insulator/Au-film and Au-pattern/weakly-absorbing-material/Au-film where Au-pattern was structured graded photonic super-crystal. We observed multiple-band absorption, including one near 1500 nm, Au-pattern/spacer/Au-film. The due gap surface plasmon polariton when spacer thickness less than 30 nm. Broadband appears insulator replaced by weakly absorbing material. E-field intensity simulated confirmed formation polaritons their coupling with Fabry–Pérot resonance.