Abstract
Scattering coefficients can diverge at spectral singularities. In such situation, the stationary solution becomes a laser solution with outgoing waves only. We explore a parity-time (PT)-symmetric non-Hermitian two-arm Aharonov-Bohm interferometer consisting of three coupled resonators enclosing synthetic magnetic flux. The synthetic magnetic flux does not break the PT symmetry, which protects the symmetric transmission. The features and conditions of symmetric, asymmetric, and unidirectional lasing at spectral singularities are discussed. We elucidate that lasing affected by the interference is asymmetric; asymmetric lasing is induced by the interplay between the synthetic magnetic flux and the system's non-Hermiticity. The product of the left and right transmissions is equal to that of the reflections. Our findings reveal that the synthetic magnetic flux affects light propagation, and the results can be applied in the design of lasing devices.
Highlights
The theory of parity-time (PT )-symmetric systems has been extensively investigated [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]
A PT -symmetric two-arm AB interferometer where three coupled resonators are embedded in a uniformly coupled resonator array is proposed in this paper
Synthetic magnetic flux is enclosed by the three coupled resonators using the pathlength imbalance method
Summary
The theory of parity-time (PT )-symmetric systems has been extensively investigated [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]. In Hermitian systems, symmetric scattering exists even in the presence of synthetic magnetic flux, where photons. The synthetic magnetic flux induces asymmetric couplings but does not break the time-reversal symmetry. In non-Hermitian systems, the synthetic magnetic flux and the non-Hermiticity can induce novel asymmetric behaviors [50]. In contrast to a perfect absorber, a PT -symmetric laser at non-Hermitian spectral singularities, where symmetrical lasing toward both sides of a scattering system occurs, has been demonstrated [40,41,55]. We focus on a PT -symmetric non-Hermitian system consisting of three coupled optical resonators and in which synthetic magnetic flux is enclosed. PT symmetry holds in the presence of synthetic magnetic flux and enables symmetric light transmission even though the coupling is asymmetric.
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