Tunable polarization-sensitive, long-wave infrared MDM subwavelength grating structure with wide-angle, narrow-band, and high absorption

This paper proposes a polarization-sensitive, metal-dielectric-metal (MDM) subwavelength grating structure based on surface plasmon resonance that achieves wide-angle, narrow-band, and high absorption in the long-infrared region. The resonance characteristics of the MDM structure, excited by magnetic resonance (MR), cause the transverse magnetic (TM) and transverse electric (TE) modes to polarize. A model of the inductor capacitor (LC) circuit is also presented. Structural simulations demonstrate a near-perfect absorption characteristic (99.99%) at 9 mu m center wavelength. For TM polarization with incident angles ranging from 0 degrees to 89 degrees, the MDM grating structure produced absorption rates over 90%, 81%, and 71% for incident angles of 66 degrees, 73 degrees, and 77 degrees, respectively. The absorption peaks in the long-wave infrared band can be adjusted by varying the duty cycle or period, without adjusting structural parameters. The spectral absorption curve shows a red shift and maintains high absorption, with wide-angle and narrow-band, across various azimuth angles (0-90 degrees), during an increase in duty cycle or period. This method reduces the difficulty and complexity of micro-nano processing, and enables multiple absorbers in the long-infrared band (7.5-13 mu m) to be processed and prepared on the same substrate surface. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement