Tunable terahertz spectral filter based on temperature controlled subwavelength InSb grating

• Localized surface plasmon resonances property of subwavelength InSb grating by thermal control.
• Dependency of InSb permittivity on temperature has been theoretically analyzed.
• The resonant frequency can be tuned from 0.425 THz to 1.364 THz by thermally controlling.
• The resonance frequencies vary in a linear fashion with respect to temperature during the range of 225–325 K.

In this paper, we theoretically investigate a tunable terahertz- (THz-) frequency filter based on sub-wavelength indium antimonide (InSb) grating by utilizing the dielectric property of InSb. Strong electric field localization on the surface of the sub-wavelength InSb grating at a certain resonant frequency is presented. This phenomenon can be attributed to the effect that arises from localized surface plasmon resonance (LSPR) excited on the surface of InSb grating by the THz wave. The resonant frequency can be tuned from 0.425 THz to 1.364 THz by thermally controlling the permittivity of the InSb grating. This shift can be attributed to the change in the permittivity of InSb with the number of thermally excited carriers. Furthermore, the resonance frequencies vary in a linear fashion with respect to temperature with the range of 225–325 K. Therefore, the desired resonance frequency can be selected and tuned in a tuning range of 900 GHz conveniently in the THz region.