Nonreciprocal Transmission Research Articles

Manipulation of Nonreciprocal Microwave Photon Transmission with Low-Pump Magnetostriction

Manipulation of Nonreciprocal Microwave Photon Transmission with Low-Pump Magnetostriction

Nonreciprocal transmission of surface acoustic waves induced by magneotoelastic coupling with an anti-magnetostrictive bilayer

In this study, we report giant nonreciprocal transmission of shear-horizontal surface acoustic waves (SH-SAWs) in a ferromagnetic bilayer structure with negative–positive magnetostriction configuration. Although the directions of magnetization in the neighboring layers are parallel, SH-SAWs can excite optical-mode spin waves (SWs) via magnetoelastic coupling at relatively low frequencies, which is much stronger than acoustic-mode SWs at high frequencies. The measured magnitude nonreciprocity or isolation of SH-SAWs exceeds 40 dB (or 80 dB/mm) at 2.333 GHz. In addition, maximum nonreciprocal phase accumulation reaches 188° (376°/mm). Our theoretical model and calculations provide an insight into the observed phenomena and demonstrate a pathway for further improving nonreciprocal acoustic devices toward highly compact microwave isolators and circulators.

Modulating nonreciprocal transmission in levitated magnomechanical systems

In this paper, we propose a model of a dual cavity magnomechanical system with two levitated yttrium iron garnet spheres to investigate nonreciprocal transmission of a microwave field. We use an external Coulomb force to bias the steady-state position of the sphere levitated in each microwave cavity, thereby establishing an independent and controllable effective couplings between the cavity modes and the magnon modes. This can break the symmetry of the system and serve as the basis for nonreciprocal transmission in this system. We demonstrated how to achieve the system nonreciprocity with an extremely high isolation ratio and flexible controllability by appropriately selecting the suspended positions of the levitated spheres, which are related to the external bias forces. We also analyze in detail the influence of the cavity detunings and the driving power on the bias-force-induced nonreciprocity. Our study provides an effective approach to manipulating flexibly nonreciprocal transmission of a microwave field and may have potential implications for the development of future nonreciprocal transmission devices.

Reciprocal or nonreciprocal bimolecular interface and quantum entanglement

We study a hybrid system of a plasmonic cavity coupled to a pair of different molecular vibration modes with the strong optomechanical-like interactions. Here, this plasmonic cavity is considered as a quantum data bus and then assist several applications. For instance, it can first establish a bimolecular interface to ensure the reciprocal or non-reciprocal information transmission, and then engineer both molecules into the steady-state quantum entanglement of the continuous variable through the dissipative method. In contrast to the traditional optomechanical system, this hybrid system can provide the stronger optomechanical-like interactions and more convenient controls to the molecular quantum units. This investigation is believed to be able to further expand the practical application range of quantum technology.

Dynamic tunable nonreciprocal single-photon scattering mediated by a giant atom assisted with a time-modulated cavity

Nonreciprocal single-photon scattering in a one-dimensional waveguide coupled to a giant two-level atom assisted with a time-modulated single-mode cavity is investigated. The analytic expressions of the single-photon scattering amplitudes are derived by using an effective Floquet Hamiltonian in real space. The scattering characteristics are discussed detail in both the Markovian and the non-Markovian regimes, and the corresponding conditions for achieving perfect nonreciprocal single-photon transmission are obtained. In the Markovian regime, a frequency-tunable single-photon diode with an ideal transmission contrast ratio can be realized by adjusting the frequency of the cavity mode, the local coupling phase difference, and the accumulated phase between the two coupling points. Furthermore, the influence of the intrinsic energy dissipations on the photon transport is discussed in detail. It is found that the dissipations of the cavity and the giant atom affect discriminatively the nonreciprocal single-photon scattering process. In the non-Markovian regime, the influence of the non-Markovian retarded effect induced by the time delay on the nonreciprocal single-photon scattering is discussed in detail. The results reveal that, although the retarded effect leads to a complex nonreciprocal scattering spectrum, dynamic tunable perfect nonreciprocal transmission with more abundant physical phenomena suitable for photons with different frequencies within a larger range can also be achieved. Such a nonreciprocal single-photon device can be used as an elementary unit for various quantum information processing and may have potential applications in quantum network engineering.

Non-Bloch band theory for time-modulated discrete mechanical systems

This study establishes a non-Bloch band theory for time-modulated discrete mechanical systems. We consider simple mass–spring chains whose stiffness is periodically modulated in time. Using the temporal Floquet theory, the system is characterized by linear algebraic equations in terms of Fourier coefficients. This allows us to employ a standard linear eigenvalue analysis. Unlike non-modulated linear systems, the time modulation makes the coefficient matrix non-Hermitian, which gives rise to, for example, parametric resonance, non-reciprocal wave transmission, and non-Hermitian skin effects. In particular, we study finite-length chains consisting of spatially periodic mass–spring units and show that the standard Bloch band theory is not valid for estimating their eigenvalue distribution. To remedy this, we propose a non-Bloch band theory based on a generalized Brillouin zone. This novel approach, the combination of the temporal Floquet theory for time-modulated systems and generalized Brillouin zone, enables the prediction of eigenvalue distribution under open boundary conditions and also quantitative characterization of non-Hermitian skin modes. The proposed theory is verified by some numerical experiments.

Nonreciprocal transmission in silicon micromechanical resonators via parity-time symmetry breaking

Nonreciprocal transmission in silicon micromechanical resonators via parity-time symmetry breaking

Drifting plasmons in two-dimensional electron channels: circuit analogy.

Plasmons in two-dimensional electron channels have potential applications in the terahertz frequency range. Equivalent circuit models provide a convenient framework for analysing the plasmons. This article introduces a circuit model for plasmons in the presence of a dc current that flows in a gated channel. It is shown that drifting plasmons can be described by an LC-transmission line with distributed dependent sources. A circuit analogue of the Dyakonov-Shur instability is demonstrated. Then, a lumped-element transmission line with dependent sources is analysed, and non-reciprocity is demonstrated for examples of a right- and a left-handed transmission line. Effects of ohmic loss are discussed. The results could be used for the design of non-reciprocal transmission line devices. This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'.

Loss-compensated non-reciprocal scattering based on synchronization

Breaking the reciprocity of wave propagation is a problem of fundamental interest, and a much-sought functionality in practical applications, both in photonics and phononics. Although it has been achieved using resonant linear scattering from cavities with broken time-reversal symmetry, such realizations have remained inescapably plagued by inherent passivity constraints, which make absorption losses unavoidable, leading to stringent limitations in transmitted power. In this work, we solve this problem by converting the cavity resonance into a limit cycle, exploiting the uncharted interplay between non-linearity, gain, and non-reciprocity. Remarkably, strong enough incident waves can synchronize with these self-sustained oscillations and use their energy for amplification. We theoretically and experimentally demonstrate that this mechanism can simultaneously enhance non-reciprocity and compensate absorption. Real-world acoustic scattering experiments allow us to observe non-reciprocal transmission of audible sound in a synchronization-based three-port circulator with full immunity against losses.

Phase-mediated single-photon scattering and nonreciprocal transmission in a coupled resonator waveguide with a three-level giant atom

We theoretically investigate single-photon scattering and nonreciprocal transmission in a coupled resonator waveguide which is coupled to a driven three-level giant atom via two distant sites. In our system, the local coupling phases are introduced to induce intriguing interference effects. As a result, the phase difference can serve as a sensitive controller for the photon scattering. It is found that the photon scattering properties can be effectively tailored by the size of the giant atom, the driving field and the phase difference. Intriguingly, by carefully tuning the parameters such as the atomic dissipation and the phase difference, a perfect nonreciprocal single-photon transmission can be realized. Additionally, the photon frequency can be adjusted by modulating Rabi frequency of the driving field. These results have significant potential for the development of nonreciprocal optical devices using the giant-atom configuration.

Nonreciprocal single-photon scattering mediated by a driven Λ-type three-level giant atom

A waveguide-QED with giant atoms, which is capable of accessing various limits of a small one, provides a new paradigm to study photon scatterings. Thus, how to achieve nonreciprocal photon transmissions via such a giant atom setup is highly desirable. In this study, the nonreciprocal single-photon scattering characteristics of a double-driven Λ-type three-level giant atom, where one of the transition couples to a 1D waveguide at two separate points, and the other is driven by two coherent driving fields, are investigated. It is found that a frequency-tunable single-photon diode with an ideal contrast ratio can be achieved by properly manipulating the local coupling phases between the giant atom and the waveguide, the accumulation phase between the two waveguide coupling points, the Rabi frequencies and phase difference of the two driven fields. Compared to the previous single driving schemes, on the one hand, the presence of the second driving field can provide more tunable parameters to manipulate the nonreciprocal single-photon scattering behavior. On the other hand, here perfect nonreciprocal transmission for photons with arbitrary frequencies is achievable by tuning the driving phases while the two driving fields keep on turning, which provides an alternative way to control the nonreciprocal single-photon scattering. Furthermore, the results reveal that both the location and width of each optimal nonreciprocal transmission window is also sensitive to the driving detuning, and a single-photon diode with wide or narrow bandwidth can be realized based on demand. These results may be beneficial for designing nonreciprocal single-photon devices based on a double-driven giant atom setup.

A nonlinear vibration isolator with an essentially nonlinear converter

This paper introduces nonlinearity into bilinear springs and proposes an efficient asymmetrical nonlinear frequency converter (NC) that has a non-reciprocal transmission, which cascades a nonlinear spring and a rope. To solve the vibration equations of both NC and the conventional NES, the Runge-Kutta method is utilized. A comparison is conducted between the amplitude attenuation rates of the NC and the conventional NES. The rate of energy dissipation is indicated by analyzing the remaining energy. According to numerical analysis results, NC has a better performance in suppressing vibration than the conventional NES within a certain range. The energy dissipation rate is higher under a wide initial condition. In addition, NC can cause energy to shift from low-frequency regions to high-frequency regions with wide frequency bands. NC has a broader frequency range and a wider range of applications. This research offers a new approach and strategy for exploring effective devices for damping vibrations.

Nonreciprocal transmission enabled by time modulation of penetrable metasurface assisted by surface waves

Nonreciprocal transmission enabled by time modulation of penetrable metasurface assisted by surface waves

Tunable microwave circulator and amplifier in cavity magnonic system

An adjustable unidirectional amplifier is proposed in a hybrid cavity magnonic system. By eliminating the rapidly dissipative auxiliary mode, we obtain the effective Hamiltonian for a typical three-body circulator. Through analyzing the transmission coefficients of the system, we find that the nonreciprocal transmission of photon–magnon as well as the amplification of arbitrary signals can be both realized without requiring in the parity-time symmetry condition. In addition, the amplification factor of our system is highly adjustable. Our theoretical scheme has potential implication in realizing magnonic triodes and magnon-based quantum information processing.

Loss-induced quantum nonreciprocity

Attribute to their robustness against loss and external noise, nonreciprocal photonic devices hold great promise for applications in quantum information processing. Recent advancements have demonstrated that nonreciprocal optical transmission in linear systems can be achieved through the strategic introduction of loss. However, a crucial question remains unanswered: can loss be harnessed as a resource for generating nonreciprocal quantum correlations? Here, we take a counterintuitive stance by engineering loss to generate a vital form of nonreciprocal quantum correlations, termed nonreciprocal photon blockade. We examine a dissipative three-cavity system comprising two nonlinear cavities and a linear cavity. The interplay of loss and nonlinearity leads to a robust nonreciprocal single- and two-photon blockade, facilitated by destructive quantum interference. Furthermore, we demonstrate the tunability of this nonreciprocal photon blockade by manipulating the relative phase between the two nonlinear cavities. Remarkably, this allows for the reversal of the direction of nonreciprocity. Our study not only sheds a light on the concept of loss-engineered quantum nonreciprocity but also opens up a pathway for the design of quantum nonreciprocal photonic devices.

Magneto-optical chiral metasurfaces for achieving polarization-independent nonreciprocal transmission.

Nonreciprocal transmission, resulting from the breaking of Lorentz reciprocity, plays a pivotal role in nonreciprocal communication systems by enabling asymmetric forward and backward propagations. Metasurfaces endowed with nonreciprocity represent a compact and facile platform for manipulating electromagnetic waves in an unprecedented manner. However, most passive metasurfaces that achieve nonreciprocal transmissions are polarization dependent. While incorporation of active elements or nonlinear materials can achieve polarization-independent nonreciprocal metasurfaces, the complicated configurations limit their practical applications. To address this issue, we propose and demonstrate a passive and linear metasurface that combines magneto-optical and chiral effects, enabling polarization-independent isolation. The designed metasurface achieves a transmittance of up to 80%, with a high contrast between forward and backward propagations. Our work introduces a novel mechanism for nonreciprocal transmission and lays the foundation for the development of compact, polarization-insensitive nonreciprocal devices.

Realisation of broadband two-dimensional nonreciprocal acoustics using an active acoustic metasurface.

Nonreciprocal acoustic devices have been shown to be able to control incident waves propagating in one direction whilst allowing incident waves propagating in the opposite direction to be transmitted without modification. Nonreciprocal sound transmission, typically, has been achieved by introducing nonlinearities or directional biasing through fluid motion or spatiotemporal modulation of resonant cavities. However, the spatial arrangement of these approaches creates preferential characteristics in one direction such that the direction of the nonreciprocal behaviour is fixed and, thus, they are not straightforwardly reconfigurable. To address this issue, it has previously been revealed that feedforward wave-based active controllers can be employed to drive a single subwavelength active unit cell to achieve broadband nonreciprocal sound transmission or absorption in a one-dimensional linear acoustic system. Extending this concept, this paper investigates how the feedforward wave-based active controller can be used to drive an array of subwavelength active unit cells forming a metasurface to achieve broadband nonreciprocal sound absorption over a two-dimensional plane. Through simulation and experimental studies, this paper shows that active wave-based absorption control systems can achieve broadband nonreciprocal sound absorption when the incident waves are generated by normally and obliquely positioned primary sources.

Manipulating the nonreciprocal microwave transmission by using a pump-induced magnon mode

We realize the electromagnetic regulation of nonreciprocal microwave transmission by introducing a pump-induced magnon mode (PIM) into a cavity magnonic device with dissipative photon–magnon coupling. As a peculiar spin wave, the PIM's dynamic properties, including its spin number and resonant frequency, can be easily tuned by the microwave pump. Hence, it facilitates the precise control of the coupling process between the PIM and the cavity magnonic device by regulating the pump signal. Along with these manipulations, the nonreciprocal microwave transmission produced by the dissipative photon–magnon coupling is regulated without reconfiguring the system. In the experiment, we achieve a pump-controlled nonreciprocal bandwidth of 16 MHz and a pump-tunable isolation range of up to 40 dB. Our work demonstrates the control of a microwave with another microwave. It has a great potential in the design of fast microwave switches and programmable isolators for information processing.

Non-reciprocal optical Tamm state in a photonic crystal heterojunction containing Weyl semimetals

In the past decades, optical Tamm states (OTSs) in photonic crystal (PC) heterojunctions containing magneto-optical materials have been widely utilized to achieve non-reciprocal transmission. Nevertheless, as incident angle increases, both forward and backward OTSs in PC heterojunctions containing magneto-optical materials shift toward shorter wavelengths (i.e., blueshift), giving rise to weak non-reciprocities. In this paper, we achieve a non-reciprocal OTS in a PC heterojunction containing Weyl semimetals (WSMs). Interestingly, as incident angle increases, the forward OTS shifts towards longer wavelengths while the backward OTS shifts toward shorter wavelengths. Therefore, the non-reciprocity can be greatly enhanced. The underlying physical mechanism can be explained by the Fabry-Perot resonant condition. Besides, the effects of the axial vector b and the loss of WSM on non-reciprocity are investigated. These results would possess great potential applications in the design of circulators and isolators.

Periodically nonreciprocal transmission and entanglement in a non-Hermitian topological phase

Periodically nonreciprocal transmission and entanglement in a non-Hermitian topological phase