Abstract
Terahertz isolators, one of the typical nonreciprocal devices that can break Lorentz reciprocity, are indispensable building blocks in terahertz systems for their critical functionality of manipulating the terahertz flow. Here, we report an integrated terahertz isolator based on the magneto-optical effect of a nonreciprocal resonator. By optimizing the magneto-optical property and the loss of the resonator, we experimentally observe unidirectional propagation with an ultrahigh isolation ratio reaching up to 52 dB and an insertion loss around 7.5 dB at ~0.47 THz. With a thermal tuning method and periodic resonances, the isolator can operate at different central frequencies in the range of 0.405–0.495 THz. This on-chip terahertz isolator will not only inspire more solutions for integrated terahertz nonreciprocal devices, but also have the feasibility for practical applications such as terahertz sensing and reducing unnecessary reflections in terahertz systems.
Highlights
Terahertz isolators, one of the typical nonreciprocal devices that can break Lorentz reciprocity, are indispensable building blocks in terahertz systems for their critical functionality of manipulating the terahertz flow
The other kind of method is based on the unidirectional absorption[26,27] and reflection[16,28], which results from the nonreciprocal directional dichroism[26,27,29,30,31] and nonreciprocal reflection loss of the magnetic materials in specific directions[16,28]
Compact, and high-efficiency terahertz systems[9,32], there is an urgent need for the realization of on-chip terahertz isolators, which has not yet been reported
Summary
One of the typical nonreciprocal devices that can break Lorentz reciprocity, are indispensable building blocks in terahertz systems for their critical functionality of manipulating the terahertz flow. Recent advances in terahertz frequencies provide both opportunities and challenges, the lack of high-efficiency terahertz sources, high-sensitivity detectors, and functional devices is still the main blocking element hindering the progress of terahertz technology[3,4,9] Among these components, nonreciprocal terahertz devices hold the possibility of breaking the time-reversal symmetry, realizing the function of irreversible terahertz propagation[10,11,12,13]. In 2016, an isolator based on the magneto-optical Kerr effect of graphene was experimentally demonstrated with an isolation ratio of ~20 dB and an insertion loss of ~7.5 dB, which was suitable for circularly polarized terahertz signals under room temperature and a magnetic field of 7 T15. In 2018, an isolator based on reflection and absorption of InSb was verified with an isolation ratio of 35 dB and an insertion loss of
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