Coherent Coupling between Phonons, Magnons, and Photons

Mechanical degrees of freedom, which have often been overlooked in various quantum systems, have been studied for applications ranging from quantum information processing to sensing. Here, we develop a hybrid platform consisting of a magnomechanical cavity and an optomechanical cavity, which are coherently coupled by the straightway physical contact. The phonons in the system can be manipulated either with the magnetostrictive interaction or optically through the radiation pressure. Together with mechanical state preparation and sensitive readout, we demonstrate the microwave-to-optical conversion with an ultrawide tuning range up to 3 GHz. In addition, we observe a mechanical motion interference effect, in which the optically driven mechanical motion is canceled by the microwave-driven coherent motion. Manipulating mechanical oscillators with equal facility through both magnonic and photonic channels enables new architectures for signal transduction between the optical, microwave, mechanical, and magnetic fields.

Figure 1

(a) Schematic of the device that consists of a YIG and a silica microsphere, which both support the mechanical modes excited by the magnetostrictive interaction through magnons or the radiation pressure induced by the circulating optical fields. Based on the straightway physical contact, the localized mechanical modes establish direct coupling. (b) Schematic of the coupling between magnons, phonons, and photons and an intuitive illustration of the magnon, phonon, and photon mode.

Figure 2

Coupling between the localized mechanical modes. (a) The measurement setup. Green lines represent optical paths, and purple, blue, and orange lines represent electrical connections. ESA, electrical spectrum analyzer; LIA, lock-in amplifier; VNA, vector network analyzer; SRC, microwave source; PD, photodetector; $\varphi$, phase shifter. (b) Optical transmission spectrum for the optical mode $c$ in the silica microsphere. (c) Displacement power spectrum of the two radial breathing modes in the single silica microsphere. (d) Measured microwave reflection spectrum of the magnon mode $m$. (e) Spectral diagram of the coherent coupling between magnons, phonons, and microwave and optical photons. (f) Measured reflection spectrum when a microwave signal is swept across the magnon mode resonance with a strong microwave drive ($76\mathrm{mW}$), which is red detuned from the magnon mode $m$ with the detuning ${\mathrm{\Delta }}_d={\omega }_d-{\omega }_m=-{\omega }_{b_1}$. (g) Microwave-driven mechanical motion spectrum $S_{21}$ obtained from the optical probing of the silica microsphere when two microcavities contacted (blue) or separated (gray).

Figure 3

Coherent mechanical motion and microwave-to-optical conversion. (a) Quadrature distributions of the mechanical state with increasing the microwave signal power. (b) Quadrature measurement of the coherent mechanical state with varying phase. (c) The microwave-to-optical conversion efficiency as a function of the microwave drive power. (d) The normalized conversion efficiency versus drive-resonance detunings ${\mathrm{\Delta }}_d$. (e) The conversion efficiency as a function of the microwave signal frequency (normalized to the efficiency of 4.8 GHz). The signal-drive detuning and drive-resonance detuning are maintained ${\mathrm{\Delta }}_{sd}=-{\mathrm{\Delta }}_d={\omega }_{b_2}$.

Figure 4

Mechanical motion interference. (a) Schematic indicating a mechanical motion interference. (b) The measurement setup. While part of the VNA output is sent to the magnon for microwave-driven mechanical motion in YIG microsphere, it is also down-converted to drive the electro-optic phase modulator (PM) for optically stimulating the phonons in silica microsphere. (c) The $S_{21}$ spectra as increasing the microwave drive power, implying the evolution of mechanical motion from optomechanical drive dominated to microwave drive dominated (from black to purple lines). (d) The $S_{21}$ spectra by varying only the phase of rf signal applied to the magnon mode and fixing both rf drive and signal power, giving rise to peak (dip) and asymmetric Fano line shapes.