Broadband Terahertz Isolator

Breaking the reciprocity in opticalsystems is enabling the possibility of implementing devices with unidirectional wave propagation. There is currently an active search for suitable material with an efficient nonreciprocal response at the terahertz (THz) frequency range. Ideally, such a material should allow low-loss operation without an external magnetic field at room temperature. Gyrotropic hexaferrite ceramic is highly promising for achieving optical isolation in the THz spectral range. Here, we demonstrate a broadband self-biased THz isolator based on magnetized aluminum-substituted barium hexaferrite. We reveal the necessary surface density of the hexaferrite sample for the realization of THz isolation. The proposed device exhibits no less than 30 dB of isolation from 0.2 to 1 THz. Moreover, we show that the gyrotropy properties of hexaferrite ceramics can be reasonably predicted by their magnetic properties. This device is expected to be useful for applications where one-way propagation of broadband THz wave is desired.