THz guided-mode resonance notch filter with variable filtering strength

In this paper, we propose a terahertz (THz) guided-mode resonance (GMR) notch filter made of a monolithic polyethylene terephthalate (PET) film, which has a monolayer grating structure. The proposed configuration shows both polarization-dependent and polarization-independent notch filter characteristics for the incident THz wave depending on the rotation angle of the second grating film. When the rotation angle is 0 degrees, the filtering strength (transmittance) at resonance frequency changes from 0.4 (0.996) to 99.0% (0.010) according to the incident polarization. The transmittance continuously decreases with increasing rotation angle until 90 degrees. When the rotation angle is 90 degrees, the transmittance converges to 0.065 (+/- 0.015) independent of the incident wave polarization. When the incident polarization angle ranges from 90 degrees to 180 degrees, paradoxically, the transmittance through the two GMR grating films is greater than the transmittance through only the first GMR grating film due to the enhancement of the vertical component of the THz wave. These results agree well with a calculation using a polar coordinate system.

Automated summary

This paper proposes a THz GMR notch filter made of a monolithic PET film with a monolayer grating structure. The filter shows polarization-dependent and polarization-independent characteristics depending on the rotation angle of the second grating film. The transmittance converges to 0.065 regardless of incident wave polarization at a rotation angle of 90 degrees.