Nonreciprocal Diffraction Research Articles

Observation of Nonreciprocal Diffraction of Surface Acoustic Wave

Observation of Nonreciprocal Diffraction of Surface Acoustic Wave

Non-reciprocal diffraction in magnetoplasmonic gratings.

Phase-matching conditions-used to bridge the wave vector mismatch between light and surface plasmon polaritons (SPPs)-have been exploited recently to enable nonreciprocal optical propagation and enhanced magneto-optic responses in magnetoplasmonic systems. Here we show that using diffraction in conjunction with plasmon excitations leads to a photonic system with a more versatile and flexible response. As a testbed, we analyzed diffracted magneto-optical effects in magnetoplasmonic gratings, where broken time-reversal symmetry induces frequency shifts in the energy and angular spectra of plasmon resonance. These result in exceptionally large responses in the diffracted magneto-optical effect. The concepts presented here can be used to develop non-reciprocal optical devices that exploit diffraction, in order to achieve tailored electromagnetic responses.

Manipulating electromagnetic wave propagating non-reciprocally by a chain of ferrite rods.

We demonstrated that non-reciprocal wave propagation could be manipulated by a magnetic rod chain under bias DC magnetic fields. Made of ferrite material YIG and designed working in the microwave X-band, the rod chain exhibited almost a total reflection when the incident wave obliquely impinged on the rod chain, but exhibited nearly a total transmission when the wave reversed its propagation direction. The non-reciprocal wave propagation was due to the non-reciprocal diffraction of the rod chain for the orders 0 and ± 1. Further, the non-reciprocal wave propagation was directly observed by using the field mapping technique. The unique non-reciprocal wave property of the magnetic rod chain provides a new way to control the flow of EM waves.

Nonreciprocal diffraction of light based on double-transition-assisted photonic Aharonov-Bohm effect

We propose a nonreciprocal diffraction system based on the photonic Aharonov-Bohm effect. The implementation utilizes the simultaneous up and down photonic transition of Bloch modes in a dielectric grating created by time-harmonic dielectric constant modulation. This double transition process generates opposite effective magnetic fluxes for photons in symmetric and antisymmetric modes, which gives rise to nonreciprocal spatial interference between them. With the broken time-reversal symmetry, this system is possible to exhibit unidirectional highly efficient diffraction, which enables grating-based nonmagnetic isolation and circulation of free space light, and integrates the functions of gratings and isolators.

Role of photonic angular momentum states in nonreciprocal diffraction from magneto-optical cylinder arrays

Optical eigenstates in a concentrically symmetric resonator are photonic angular momentum states (PAMSs) with quantized optical orbital angular momentums (OAMs). Nonreciprocal optical phenomena can be obtained if we lift the degeneracy of PAMSs. In this article, we provide a comprehensive study of nonreciprocal optical diffraction of various orders from a magneto-optical cylinder array. We show that nonreciprocal diffraction can be obtained only for these nonzero orders. Role of PAMSs, the excitation of which is sensitive to the directions of incidence, applied magnetic field, and arrangement of the cylinders, are studied. Some interesting phenomena such as a dispersionless quasi-omnidirectional nonreciprocal diffraction and spikes associated with high-OAM PAMSs are present and discussed.

Nonreciprocal diffraction through dielectric gratings with two-dimensional chirality

It is generally assumed that the propagation of light through a dielectric medium is always reciprocal under reversal of the propagation direction. We show that in an all-dielectric diffractive system nonreciprocal polarization changes are possible for individual diffracted beams when the diffractive medium possesses two-dimensional chirality. This nonreciprocity is characterized by different eigenstates for the system for the forward and reverse directions respectively, yet it is also entirely consistent with the predictions of the Lorentz reciprocity lemma.

Beam Dynamics inPTSymmetric Optical Lattices

The possibility of parity-time (PT) symmetric periodic potentials is investigated within the context of optics. Beam dynamics in this new type of optical structures is examined in detail for both one- and two-dimensional lattice geometries. It is shown that PT periodic structures can exhibit unique characteristics stemming from the nonorthogonality of the associated Floquet-Bloch modes. Some of these features include double refraction, power oscillations, and eigenfunction unfolding as well as nonreciprocal diffraction patterns.

Nonreciprocal diffraction by spatial modulation of absorption and refraction

Linear diffraction gratings that provide strongly asymmetric diffraction without surface modulation are created and studied. The spatial phase shift of the refractive-index grating relative to the absorption grating is the origin of nonreciprocal behavior.

Spatial separation of opposite waves in a ring laser

A transverse spatial separation of opposite waves in a solid-state ring laser with a homogeneously broadened luminescence line of the active substance was observed on increase in the difference between the frequencies of the ring resonator. This made it possible to reduce the competition between the opposite waves and to control the transverse structure of the solid-state laser radiation without altering the resonator geometry. The spatial separation of the opposite waves and the operating regimes of the laser could be altered also by means of nonreciprocal diffraction effects.