Terahertz wave asymmetric transmission based on double-layer subwavelength dielectric grating

A double-layer subwavelength dielectric grating has been designed, fabricated, and characterized for terahertz (THz) wave asymmetric transmission. The subwavelength grating resonance effect and the first-order diffraction effect of the two different grating structures lead to the different light paths of the forward and backward waves, and thus the one-way transmission can be realized. The transmission and resonance properties of this grating with different polarization and propagation directions have been demonstrated experimentally and theoretically, which show that this is a nonmagnetic one-way transmission device with an extinction ratio of over 15 dB and insertion loss of lower than 5 dB at 1.45 THz. We provide an effective way to nonmagnetic THz asymmetric transmission devices operating at room temperature without rotating or converting the polarization state of incident wave.