The Faraday effect due to the cyclotron resonance of conduction electrons in semiconductor InSb allows for nonreciprocity of transmitted light in our Faraday THz isolator operating in the presence of a small magnetic field. We select InSb as an efficient medium for our isolator due to its high electron mobility, low electron effective mass, and narrow band gap. Experimental measurements of the isolator performance indicate a maximum achieved isolation power of 18.8 dB with an insertion loss of −12.6 dB. Our optical analysis of the device points to a remarkable nonreciprocal Fabry-Perot effect in the magneto-optical InSb layer as the origin of the multi-fold isolation enhancement. This nonreciprocity occurs as the Fabry-Perot reflections in the forward direction add constructively and enhance the transmittance at certain frequencies, while the Fabry-Perot reflections in the backward direction add destructively and suppress the transmittance at the same frequencies.
Broken spatial and time reversal symmetries in materials often give
rise to new emergent phenomena in the interaction between light and
matter. The combination of chirality and broken time reversal symmetry
in a magnetic field leads to magneto–chiral phenomena, such as
the nonreciprocity of transmission. Here, we construct a terahertz
hybrid metamaterial that combines the natural optical activity of a
chiral metallic gammadion bilayer and the magneto-optical activity of
semiconductor indium antimonide in a magnetic field. We report a
resonant magneto–chiral effect that leads to
polarization-independent nonreciprocal optical transmittance.
Furthermore, we discover a magneto-optical Faraday effect that is
resonantly controlled by the natural optical activity of the chiral
gammadion bilayer. Unlike optical activity due to chirality, the novel
Faraday effect is odd under time reversal. Both phenomena are
activated by a modest magnetic field, which may open doors for their
potential applications in polarization-independent optical isolation
and highly efficient polarization control at terahertz
frequencies.
We report the observation of a long-lived birefringent state in quantum paraelectric KTaO3 induced by THz pump pulses in a two-THz-photon process. We relate this long-lived state to the proximity of the ferroelectric phase transition.
We achieve tunable nonreciprocal directional dichroism at terahertz frequencies without breaking the spatial inversion symmetry by combining an Archimedean spiral metasurface and the magneto-optical effect in indium antimonide (InSb) in one hybrid metamaterial.
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