Salisbury Screen Terahertz Absorber Formed with an Insulator: 4‑N,N‑Dimethylamino-4′‑N′‑methyl-stilbazolium Tosylate (DAST)

A novel Salisbury screen absorber (SSA) based on a 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium tosylate (DAST) crystalline film was designed and fabricated. Different from the conventional SSA, an insulating organic DAST film replaced the normally highly conductive top surface metal layer. The absorption spectra and the structure of this SSA were optimized with a transmission line model to correspond to the DAST absorption peak at 1.1 THz, whose results were further verified by numerical simulations. If the thickness of the DAST film is 4 μm, a nearly perfect terahertz (THz) absorption is possible with this strategy, whereas the absorption of a bare 4 μm thick DAST film would be 4 times lower. The design allows the terahertz response of this DAST system to be tuned by adjusting either the thickness of the DAST film or the spacer, both of which remain in deep sub-wavelength to broaden the range of applications.