Auxiliary-cavity-enhanced quantum estimation of optorotational-coupling strength.

A scheme is proposed to achieve significantly enhanced quantum estimation of optorotational-coupling (ORC) strength by coupling a driven auxiliary cavity to a Laguerre-Gaussian (L-G) rotational cavity, where the ORC originates from the exchange of orbital angular momentum between a L-G light and rotational mirror. The results indicate that, by appropriately designing the auxiliary-cavity mechanism, the estimation error of the ORC parameter is significantly reduced, and revealing the estimation precision has a much stronger thermal noise and dissipation robustness in comparison with the unassisted case. Our study paves the way toward achieving high-precision quantum sensors.

Magnon laser based on Brillouin light scattering.

An analogous laser action of magnons has become a subject of interest, and it is crucial for the study of nonlinear magnons spintronics. In this Letter, we demonstrate the magnon laser behavior based on Brillouin light scattering in a ferrimagnetic insulator sphere, which supports optical whispering gallery modes and magnon resonances. We show that the excited magnon plays what has traditionally been the role of the Stokes wave and is coherently amplified during the Brillouin scattering process, making the magnon laser possible. Furthermore, the stimulating excited magnon number increasing exponentially with the input light power can be manipulated by adjusting the external magnetic field. In addition to providing insight into magneto-optical interaction, the study of the magnon laser action will help to develop novel, to the best of our knowledge, technologies for handling spin-wave excitations, and it could affect scientific fields beyond magnonics. Potential applications range from preparing coherent magnon sources to operating on-chip functional magnetic devices.

Nanoparticle-mediated chiral light chaos based on non-Hermitian mode coupling.

Non-Hermitian physics basically due to the interplay between gain and loss has attracted considerable attention in the context of understanding various brand-new and counterintuitive physical phenomena. The major emphasis of this work is concerned with the chirality properties of chaotic motion in a whispering-gallery-mode microresonator based on nanoparticle-induced non-Hermitian mode coupling, which will be a challenging endeavor that is rarely presented in previous literature. By operating the nanoparticles in a whispering-gallery-mode microresonator, we achieved a dynamic control of chaotic behavior, and a rather more exotic finding is that the chaotic motion features chiral characteristics. Our results provide insight into nonlinear nano-optomechanics and fundamentally broaden the regime of chaotic dynamics. In addition, the proposal of chiral light chaos may offer attractive new prospects for the development of on-chip manipulation of chaotic light propagation and chiral photonic crystals, and could affect nanoscientific fields beyond optics.

Mechanical exceptional-point-induced transparency and slow light.

Recently, the conception of PT symmetry has attracted considerable attention in various fields such as optics, acoustics, and atomic physics because of the existence of exceptional point (EP) and its importance in understanding non-Hermitian physics. Here, we propose a new scheme of investigating the mechanical-EP-induced transparency and tunable fast-to-slow light phenomena in PT-symmetric mechanical systems. We find that (i) the transmission of the probe field changes from singleto double transparency windows via the transition from a broken mechanical PT-symmetric phase to an unbroken mechanical PT-symmetric phase; (ii) the efficiency of transparency can be significantly enhanced about three orders of magnitude in the vicinity of the mechanical EP, compared to passive mechanical resonators system; and (iii) the mechanical EP can not only amplify the group delay, but also manipulate the switch from slow light to fast light, which may offer an approach to achieve the practical application of slow light and relevant to the optical switcher and communication network. Our results reveal that the exotic properties of the mechanical EP can result in enormous enhancement of the transmitted probe power and novel steering of fast and slow light.

Magnetically controllable slow light based on magnetostrictive forces.

The magnetostrictive effect provides an opportunity for exploring fundamental phenomena related to the phonon-magnon interaction. Here we show a tunable slow light in a cavity magnetomechanical system consisting of photon, magnon and phonon modes with a nonlinear phonon-magnon interaction, which originates from magnetostrictive forces. For a strong photon-magnon coupling strength, we can observe a transparency (absorption) window for the probe by placing a strong control field on the red (blue) detuned sideband of the hybridized modes, which are comprised of photons and magnons. In this work, we mainly show the characteristic changes in dispersion in the range of the transparency window. The value of group delay can be continuously adjusted by using different frequencies of magnon, which are determined by the external bias magnetic field and therefore can be conveniently tuned in a broad range. Both the intensity and the frequency of the control field have an influence on the transformation from subluminal to superluminal propagation and vice versa. Furthermore, one may achieve long-lived slow light (group delay of millisecond order) by enlarging the pump power. These results may find applications in information interconversion based on coherent coupling among photons, phonons and magnons.

Phase-mediated magnon chaos-order transition in cavity optomagnonics.

Magnon as a quantized spin wave has attracted extensive attention in various fields of physics, such as magnon spintronics, microwave photonics, and cavity quantum electrodynamics. Here, we explore theoretically the magnon chaos-order transition in cavity optomagnonics, which still remains largely unexplored in this emerging field. We find that the evolution of magnon experiences the transition from order to period-doubling bifurcation and finally enters chaos by adjusting the microwave driving power. Different from normal chaos, the magnon chaos-order transition proposed here is phase mediated. Beyond their fundamental scientific significance, our results will contribute to the comprehension of nonlinear phenomena and chaos in optomagnonical systems, and may find applications in chaos-based secure communication.

Highly Sensitive Charge Sensor Based on Atom-Assisted High-Order Sideband Generation in a Hybrid Optomechanical System.

Realizing highly sensitive charge sensors is of fundamental importance in physics, and may find applications in metrology, electronic tunnel imaging, and engineering technology. With the development of nanophotonics, cavity optomechanics with Coulomb interaction provides a powerful platform to explore new options for the precision measurement of charges. In this work, a method of realizing a highly sensitive charge sensor based on atom-assisted high-order sideband generation in a hybrid optomechanical system is proposed. The advantage of this scheme is that the sideband cutoff order and the charge number satisfy a monotonically increasing relationship, which is more sensitive than the atom-free case discussed previously. Calculations show that the sensitivity of the charge sensor in our scheme is improved by about 25 times. In particular, our proposed charge sensor can operate in low power conditions and extremely weak charge measurement environments. Furthermore, phase-dependent effects between the sideband generation and Coulomb interaction are also discussed in detail. Beyond their fundamental scientific significance, our work is an important step toward measuring individual charge.

Magnon-induced high-order sideband generation.

Magnon Kerr nonlinearity plays a crucial role in the study of an optomagnonical system and may bring many interesting physical phenomena and important applications. In this Letter, we report the investigation of high-order sideband generation induced by magnon Kerr nonlinearity in an optomagnonical system, which is still unexplored in this emerging research field. We uncover that the microwave driving field plays a significant role in manipulating the generation and amplification of the higher-order sidebands and, more importantly, the sideband spacing can be regulated by controlling the beat frequency between the pump laser and the probe laser, which is extremely eventful for the spacing modulation of the sideband frequency comb. Based on the recent experimental progress, our results will deepen our cognition into optomagnonical nonlinearity and may find fundamental applications in optical frequency metrology and optical communications.

Magnon-induced transparency and amplification in 𝒫𝒯-symmetric cavity-magnon system.

Recent research on parity-time- (𝒫𝒯-) symmetric optical structures have exhibited great potential for achieving distinctive optical behaviour which is unattainable with ordinary optical systems. Here we propose a 𝒫𝒯-symmetric cavity-magnon system consisting of active cavity mode strongly interacting with magnon to study magnon-induced transparency (MIT) and amplification (MIA) by exploiting recent microwave-cavity-engineered ferromagnetic magnons. We find that (i) due to the gain-induced enhancement of coherent coupling between the cavity field and the magnon, the transmitted probe power is remarkably enhanced about four orders of magnitude and the bandwidth also becomes much narrower, compared to passive cavity system. (ii) More importantly, the light transmission can be well controlled by adjusting the applied magnetic field without changing other parameters, and a Lorentzian-like spectra can be established between the transmitted probe power and the external magnetic field, which provides an additional degree of freedom to realize the coherent manipulation of optical transparency and amplification. Our results may offer an approach to make a low-power magnetic-field-controlled optical amplifier in 𝒫𝒯-symmetric cavity-magnon system.

A proposed method to measure weak magnetic field based on a hybrid optomechanical system.

Optomechanical systems have long been considered in the field of precision measurement. In this work, measurement of weak magnetic field in a hybrid optomechanical system is discussed. In contrast to conventional measurements based on detecting the change of magnetic flux, our scheme presents an alternative way to measure the magnetic field with a precision of 0.1 nT. We show that the effective cavity resonance frequency will be revised due to the electromagnetic interactions. Therefore, a resonance valley in the transmission spectrum of the probe field will shift in the presence of the magnetic field, and the width of an asymmetric transparency in the optomechanically induced transparency (OMIT) shows a strong dependence on the magnetic field strength. Our results may have potential application for achieving high precision measurement of the magnetic field.

Highly sensitive optical sensor for precision measurement of electrical charges based on optomechanically induced difference-sideband generation.

Difference-sideband generation in an optomechanical system coupled to a charged object is investigated beyond the conventional linearized description of optomechanical interactions. An exponential decay law for difference-sideband generation in the presence of electric interaction is identified which exhibits more sensitivity to electrical charges than the conventional linearized effects. Using the exact same parameters with previous work based on the linearized dynamics of the optomechanical interactions, we show that optomechanically induced difference-sideband generation may enable an all-optical sensor for precision measurement of electrical charges with higher precision and lower power. The proposed mechanism is especially suited for on-chip optomechanical devices, where nonlinear optomechanical interaction in the weak coupling regime is within current experimental reach.