THz bandpass filter based on sub-wavelength holes in free-standing metal thin-films

The design of a free-standing (substrate-less) metallic hole array is proposed for Terahertz frequencies. The bandpass filtering effect through free standing perforted Aluminium (Al) films is demonstrated using a square array of circular holes on Al films having thickness of ∼ 11 μm. The effect of variation of periodicity and hole diameter on the transmittance due to excitation of surface plasmons and coupling between resonant and non-resonant modes is studied.