Nature Commun. 4, 2407 (2013)
Non-reciprocal systems that break time-reversal symmetry are critical for the realization of devices like optical isolators that prohibit the propagation of light in the backward direction. This isolation effect is not attainable using conventional structures such as passive diffraction gratings; instead, a magneto-optical effect or nonlinear process is required. However, the various techniques available for realizing isolation suffer from challenges or limitations associated with integration, miniaturization, and the optical power and frequency range of operation. Dimitrios Sounas and colleagues from the University of Texas, Austin (USA) and the École Polytechnique de Montréal (Canada) have now demonstrated an alternative approach for introducing a non-reciprocal effect. They show that the limitations of present techniques may be overcome by employing angular-momentum-biased metamaterials and time-dependent modulation. They propose a scheme in which spatiotemporal modulation may provide a non-reciprocal response in Fano-resonator structures. The team suggests that this approach will allow a giant nonreciprocal response to be generated without applying an external magnetic bias.
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