Cavity Optomagnonics Research Articles

Microwave‐to‐Optical Conversion and Amplification in Cavity Optomagnonics System

Microwave‐to‐Optical Conversion and Amplification in Cavity Optomagnonics System

Stretchable complementary split-ring resonator using liquid metal and its application for cavity optomagnonics

Split-ring resonators (SRRs) and complementary split-ring resonators (CSRRs) are widely used in microwave devices. Considering its advantages of fluidity, high metallic conductivity, and extreme deformability, liquid metal is expected to enrich the tunability of SRR and CSRR. Here, a stretchable resonator based on CSRR, using liquid metal as the conducting layer and Ecoflex as the dielectric layer, is prepared by 3D printing. From the transmission spectra, we find that the resonant frequency can be continuously tuned from 3.77 to 3.40 GHz by stretching the resonator, which exhibits a stable quality factor, high ductility, excellent stretchability, and linearity. We then study the coupling between magnons in a yttrium iron garnet film and microwave photons in CSRRs. The anti-crossing effects are observed in transmission coefficient spectra by changing either the strength of the magnetic field or the size of the CSRR. The coupling strength g/2π is determined to be 63 MHz at a coupling frequency of 3.77 GHz and magnetic field of 800 Oe. Our findings could promote the development of reconfigurable metamaterials and cavity optomagnonics.

Polarization-engineered photon statistics and its tomography via optomagnonic interaction.

Cavity optomagnonics has received considerable research interest in recent years, due to the coherent magnetic Brillioun light scattering in the ferromagnetic material. Here, we theoretically propose and numerically verify a feasible scheme for the full polarization tomography on photon statistics in an optomagnonic whispering-gallery-mode microresonator system in the weak-coupling regime. By performing the polarization pre- and post-selections to manipulate the polarization states of the input and output photons, we find that the rich sub- and super-Poissonian photon statistics can be selectively generated, thanks to quantum interferences. In the parameter space of phase delay, the evolution from photon bunching to antibunching indicates the change from phase to amplitude squeezing. Our obtained result has potential applications in tunable quantum polarized light sources based on the cavity optomagnonic platform in micro-nano scale. It also offers a deeper understanding for full quantum cavity optomagnonics.

Nonreciprocal P T-symmetric magnon laser in spinning cavity optomagnonics.

We propose a scheme to achieve nonreciprocal parity-time (P T)-symmetric magnon laser in a P T-symmetric cavity optomagnonical system. The system consists of active and passive optical spinning resonators. We demonstrate that the Fizeau light-dragging effect induced by the spinning of a resonator results in significant variations in magnon gain and stimulated emitted magnon numbers for different driving directions. We find that utilizing the Fizeau light-dragging effect allows the system to operate at ultra-low thresholds even without reaching gain-loss balance. A one-way magnon laser can also be realized across a range of parameters. High tunability of the magnon laser is achieved by changing the spinning speed of the resonators and driving direction. Our work provides a new way to explore various nonreciprocal effects in non-Hermitian magnonic systems, which may be applied to manipulate photons and magnons in multi-body non-Hermitian coupled systems.

Optical quadrature squeezing via the Faraday effect in cavity optomagnonics

Coherently manipulating quadrature squeezing is highly desired for precision measurement applications, but remains challenging due to an inaccessible standard quantum limit in most micro- and nanostructures. Here, we propose an efficient scheme to generate quadrature squeezing in a cavity optomagnonical system. Taking the magnon–photon interaction induced by the Faraday effect into consideration, we report that a strong quadrature squeezing can be achieved in the effective resonant cavity modes that obey the mode-splitting theory of Bogoliubov transformation. Using experimentally achievable parameters, we illustrate that increasing the magnon–photon coupling strength or input field intensity contributes to improving both the output spectral intensity and the amount of squeezing of the spectra, where perfect squeezing is only located at the position of the single resonant cavity mode. Interestingly enough, the nearly perfect quadrature squeezing at the double frequencies of the effective resonant cavity modes can be achieved by adjusting the input field frequency and intensity.

Magnon statistical properties in multiphoton-catalyzed optomagnonics

Generating magnon states with the nonclassical behavior is a key step of implementing quantum magnonic technologies for applications. We proposed a strategy of magnonic state production by using the conditional measurement, derived from the jointed action of a cavity optomagnonics device and a beam splitter. At the case of the quantum catalysis applying to the optical field of optomagnonic system, the characters of yielding catalyzed state rely not only upon the parameters of optomechanic system but also upon the catalysis photon number and the beam splitter angle. We theoretically create a kind of the catalyzed photon–magnon entangled state and examine the statistical properties of the magnon mode of two mode optomagnonic states in the fields of the mean magnon number, the magnon number distribution, the Mandel Q parameter, the second-order autocorrelation function and the Wigner function. We demonstrate that the sub-Poisson distribution, the antibunching effect and the Wigner function negativity in the magnons can be realized via multiphoton catalysis. We also find that the magnon nonclassical statistical feature may be regulated by adjusting parameters of photon catalysis. Our work will provide a good reference for producing magnonic nonclassical state.

Eigenstates and temporal dynamics in cavity optomagnonics

Many studies of magnon–photon coupling are performed in the frequency domain for microwave photons. In this work, we present analytical results of eigenfrequency, eigenstates, and temporal dynamics for the coupling between ferromagnetic magnon and visible photon. In contrast to microwave photons, optical photons can be coupled with magnon in a dispersive interaction which produces both level repulsion and attraction by varying the magnon–photon frequency detuning. At resonance, the hybridized states are of linear polarization and circular polarization for level repulsion and level attraction respectively. As the detuning increases, the polarizations of level repulsion remain linear but those of level attraction vary from elliptical to linear polarizations. The temporal dynamics of level repulsion presents the beat-like behavior. The level attraction presents monotonous decay in the weak coupling regime but gives rise to instability in the strong coupling regime due to the magnon amplification. As the detuning is large, both magnon and photon amplitudes present a synchronizing oscillation. Our results are important for exploring the temporal evolution of magnon–photon coupling in the range of optical frequency and designing magnon-based timing devices.

All-optical polarization-state engineering in quantum cavity optomagnonics

We theoretically propose an optical polarization-state engineering based on a cavity optomagnonic platform in the full quantum regime. Here, the optomagnonic interaction can be realized in an yttrium iron garnet (YIG) sphere, which supports both two traveling-photon modes with orthogonal linear polarizations [i.e., horizontally ($H$-) and vertically ($V$-) polarized photon modes] and a Kittel magnon mode. In our scheme, the magnons mediate the photons during polarization conversions, and break the time-reversal symmetry in mutual interconversions. Through a triple resonance between the magnon mode, $H$-polarized, and $V$-polarized photon modes within the YIG optomagnonic cavity, we demonstrate an all-optical scheme to manipulate the optical polarization behaviors by adjusting an external driving laser, finding that the polarization states of the output light can be well mapped to the whole Poincar\'e sphere and a large polarization rotation of the output light with photon antibunching and superbunching can be achieved easily for a range of realistic parameters. We find the strong discrepancy in the polarization response between the exact numerical calculation using the full quantum master equation and the semiclassical approximation. In addition, we reveal the magnon-induced broken time-reversal symmetry, which connects the quantum cavity optomagnonics to the classical magneto-optical effect. Our obtained results have potential application in quantum polarization-state engineering, and also offer a further understanding for cavity optomagnonics at the quantum level.

Generation of robust optical entanglement in cavity optomagnonics.

We propose a scheme to realize robust optical entanglement in cavity optomagnonics, where two optical whispering gallery modes (WGMs) couple to a magnon mode in a yttrium iron garnet (YIG) sphere. The beam-splitter-like and two-mode squeezing magnon-photon interactions can be realized simultaneously when the two optical WGMs are driven by external fields. Entanglement between the two optical modes is then generated via their coupling with magnons. By exploiting the destructive quantum interference between the bright modes of the interface, the effects of initial thermal occupations of magnons can be eliminated. Moreover, the excitation of the Bogoliubov dark mode is capable of protecting the optical entanglement from thermal heating effects. Therefore, the generated optical entanglement is robust against thermal noise and the requirement of cooling the magnon mode is relaxed. Our scheme may find applications in the study of magnon-based quantum information processing.

Nonclassicality of dissipative cavity optomagnonics in the presence of Kerr nonlinearities

The phenomena of photon and magnon blockade, and nonclassicality which are the key ingredient for quantum enhanced technologies, can be considered as resources in quantum information processing. This paper deals with the study of nonclassicality in a lossy optomagnonic microcavity enclosed by Kerr medium, with considering different sources of dissipation. The system contains a ferromagnetic YIG sphere coupled to two optical modes in a microcavity, with photonic and magnonic Kerr nonlinearity in the presence of magnonic and photonic losses. Considering the Heisenberg-Langevin approach, we obtain the dynamics of the second-order correlation functions (CFs) to observe the phenomenon of photon and magnon blockade (PMB), and the Cauchy-Schwarz inequality (CSI) to find the nonclassicality of the system. We then discuss the effects of magnon-photon coupling strength and different sources of dissipation on the temporal behavior of the mentioned criteria. Looking at the numerical results, we find that the depth and the domain of antibunching behavior significantly depend on the value of the thermal average photon (magnon) number. The phenomenon of perfect PMB may also be observed in the presence of dissipation at the low-temperature regime where the equilibrium thermal photon (magnon) occupation number approaches zero, i.e. T → 0. Moreover, we see a strong anticorrelation between the photonic and magnonic modes and the optical modes, too. Furthermore, it can be found that the phenomenon of PMB blockade as well as antibunching can be observed at cryogenic temperatures.

Optomagnonic frequency combs

Optical frequency combs are fundamentally important in precision measurement physics, bringing unprecedented capabilities of measurements for time keeping, metrology, and spectroscopy. In this work, we investigate theoretically the formation of a form of frequency combs in cavity optomagnonics, in which a ferrimagnetic insulator sphere supports optical whispering gallery modes for both light photons and magnons. Numerical simulations of the optomagnonic dynamics show that a robust frequency comb can be obtained at low power under the bichromatic pumping drive, and the comb spacing is adjustable. Furthermore, the optomagnonic frequency comb structure has abundant non-perturbative features, suggesting that the magnon-induced Brillouin light scattering process in cavity optomagnonics may also exhibit phenomena similar to those in atomic–molecular systems. In addition to providing insight into optomagnonic nonlinearity, optomagnonic frequency combs may also provide the feasibility of implementing frequency combs based on spintronic platforms and may find applications for precision metrology based on magnonic devices.

Nonreciprocal photon blockade in cavity optomagnonics

We study nonreciprocal photon blockade in cavity optomagnonics, where a sphere of ferromagnetic crystal supports two optical whispering-gallery modes and one magnon mode. The interaction in cavity optomagnonics is subject to the selection rules involving conservation of angular momentum and energy, and the selection rules introduce a nonreciprocal coupling between linearly polarized photons and magnons. For given incident linearly polarized photons, the photon blockade occurs when the cavity is driven in one direction, but it disappears if the cavity is driven in the opposite direction. The results suggest that cavity optomagnonics could be a promising platform for studying chiral quantum optics and topological photonics.

Non‐Classical Correlations between Single Photons and Magnons

AbstractA scheme is proposed to realize the non‐classical correlation between magnons and photons in a cavity optomagnonic system, which supports both photon modes and a magnon mode. Starting with the system being initially prepared in its ground state, two laser pulses successively drive corresponding optical mode. A two‐mode squeezing interaction between optical mode 1 and the magnon mode is created by the first pulse, which leads to a non‐classical correlation between photons and magnons. To verify this non‐classical correlation, the second pulse is utilized to transfer the magnon state to another optical mode, thus the correlated photon–photon pairs are generated out of the cavity. By discussing the violation of Cauchy–Schwarz inequality, based on numerical simulation, it is confirmed that non‐classical correlated photon–magnon pairs can be created in the weak coupling regime, which relaxes the requirements of experimental conditions. The result indicates that cavity optomagnonics can be a promising platform for studying magnon‐based quantum information processing.

Recent progress on optomagnetic coupling and optical manipulation based on cavity-optomagnonics

Recently, the photon—magnon coherent interaction based on the collective spins excitation in ferromagnetic materials has been achieved experimentally. Under the prospect, the magnons are proposed to store and process quantum information. Meanwhile, cavity-optomagnonics which describes the interaction between photons and magnons has been developing rapidly as an interesting topic of the cavity quantum electrodynamics. Here in this short review, we mainly introduce the recent theoretical and experimental progress in the field of optomagnetic coupling and optical manipulation based on cavity-optomagnonics. According to the frequency range of the electromagnetic field, cavity optomagnonics can be divided into microwave cavity optomagnonics and optical cavity optomagnonics, due to the different dynamics of the photon—magnon interaction. As the interaction between the electromagnetic field and the magnetic materials is enhanced in the cavity-optomagnonic system, it provides great significance to explore the nonlinear characteristics and quantum properties for different magnetic systems. More importantly, the electromagnetic response of optomagnonics covers the frequency range from gigahertz to terahertz which provides a broad frequency platform for the multi-mode controlling in quantum systems.

Proposal for a Bell test in cavity optomagnonics

We present a proposal to test Bell inequality in the emerging field of cavity optomagnonics, where a sphere of ferromagnetic crystal supports two optical whispering gallery modes and one magnon mode. The two optical modes are driven by two laser pulses, respectively. Entanglement between magnon mode and one of the two optical modes will be generated by the first pulse, and the state of magnon mode is subsequently mapped into another optical mode via the second pulse. Hence correlated photon-photon pairs is created out of the cavity. A Bell test can be implemented using these pairs, which enables us to test local hidden-variable models at macroscopic optomagnonical system. Our results show that a significant violation of Bell inequality can be obtained in the experimentally relevant weak-coupling regime. The violation of Bell inequality not only verifies the entanglement between magnons and photons, but also implies that cavity optomagnonics is a promising platform for quantum information processing tasks.

Non-reciprocal optical transmission in cavity optomagnonics

We study the non-reciprocal optical transmission in a cavity optomagnonic system, where a ferromagnetic sphere can support both the whispering gallery modes (WGMs) for photons and the magnetostatic modes for magnons. Our scheme is based on the non-reciprocal Brillouin light scattering, where the WGMs are unidirectionally coupled to the Kittel mode with a nonzero z component of the total angular momentum. We show that a weak probe field can be transmitted or amplified in a given propagation direction, but completely absorbed in the opposite direction. The present work may provide an alternative method for the development of chiral optical devices.

Optical signatures of the coupled spin-mechanics of a levitated magnetic microparticle

We propose a platform that combines the fields of cavity optomagnonics and levitated optomechanics to control and probe the coupled spin-mechanics of magnetic dielectric particles. We theoretically study the dynamics of a levitated Faraday-active dielectric microsphere serving as an optomagnonic cavity, placed in an external magnetic field and driven by an external laser. We find that the optically driven magnetization dynamics induces angular oscillations of the particle with low associated damping. Further, we show that the magnetization and angular motion dynamics can be probed via the power spectrum of the outgoing light. Namely, the characteristic frequencies attributed to the angular oscillations and the spin dynamics are imprinted in the light spectrum by two main resonance peaks. Additionally, we demonstrate that a ferromagnetic resonance setup with an oscillatory perpendicular magnetic field can enhance the resonance peak corresponding to the spin oscillations and induce fast rotations of the particle around its anisotropy axis.

Polarization Dependent Scattering in Cavity Optomagnonics.

The polarization dependence of magnon-photon scattering in an optical microcavity is reported. Because of the short cavity length, the longitudinal mode-matching conditions found in previously explored, large path-length whispering gallery resonators are absent. Nonetheless, for cross-polarized scattering a strong and broadband suppression of one sideband is observed. This arises due to an interference between the Faraday and second-order Cotton-Mouton effects. To fully account for the suppression of the cross-polarized scattering, it is necessary to consider the squeezing of magnon modes intrinsic to thin-film geometry. A copolarized scattering due to Cotton-Mouton effect is also observed. In addition, the magnon modes involved are identified as Damon-Eshbach surface modes, whose nonreciprocal propagation could be exploited in device applications. This Letter experimentally demonstrates the important role of second-order Cotton-Mouton effect for optomagnonic devices.

Remote magnon entanglement between two massive ferrimagnetic spheres via cavity optomagnonics

Recent studies show that hybrid quantum systems based on magnonics provide a new and promising platform for generating macroscopic quantum states involving a large number of spins. Here, we show how to entangle two magnon modes in two massive yttrium-iron-garnet (YIG) spheres using cavity optomagnonics, where magnons couple to high-quality optical whispering gallery modes supported by the YIG sphere. The spheres can be as large as 1 mm in diameter and each sphere contains more than ${10}^{18}$ spins. The proposal is based on the asymmetry of the Stokes and anti-Stokes sidebands generated by the magnon-induced Brillouin light scattering in cavity optomagnonics. This allows one to utilize the Stokes and anti-Stokes scattering process, respectively, for generating and verifying the entanglement. Our work indicates that cavity optomagnonics could be a promising system for preparing macroscopic quantum states.

Nanoscatterer-mediated frequency combs in cavity optomagnonics

In non-Hermitian systems, the eigenfrequency of resonance modes coalesces at the exceptional points (EPs) in the frequency domain, leading to extraordinary parametric sensitivity. In this study, the controllable generation of high-order sidebands and frequency combs is investigated in the optomagnonical system, which comprises a single optomagnonical resonator coupled with two nanotips. Exploiting the scattering induced by the nanotips, the EPs periodically emerge as the relative angle of the two nanoscatterers in the system is tuned, and the sidebands' spectrum could be modified significantly. Moreover, we uncover that the driving field plays an essential role in controlling the orders and amplitudes of the sidebands. In particular, the generation of the frequency combs can be controlled by the external magnetic field, which determines the precession frequency of the spin. This study provides a potential method to manipulate the optical nonlinearity and to apply this method in the fields of optical communications and information processing.