Non‐Reciprocity in High‐Q Ferromagnetic Microspheres via Photonic Spin–Orbit Coupling

Abstract

Non‐reciprocal devices serving as fundamental elements in photonic and microwave circuits have attracted great attention for its applications in both classical and quantum information processing. The spin–orbit coupling (SOC) of light in microstructures shows that the polarization affects and controls the spatial degrees of freedom of light, which could been exploited to break the reciprocity of light transmission. Here, non‐reciprocal light transmission is demonstrated experimentally in high‐quality factor yttrium iron garnet microspheres via photonic SOC and Faraday effect. By applying an magnetic field in the vertical direction of resonator equator, the degeneracy of the clockwise and counter‐clockwise whispering gallery modes are lifted. The non‐reciprocal effect is shown for both polarizations and promises applications including non‐reciprocal photonic devices, magneto‐optic modulators, and magnetometers.

Single-sideband microwave-to-optical conversion in high-Q ferrimagnetic microspheres

“…The input light couples to the YIG microcavity and excites the WGMs through the high-index prism. The WGMs in microcavity will have a spin along the z direction due to the spinorbit coupling of light [33][34][35]. According to our previous work, the spin will be modulated by the magnetization along z direction due to Faraday effect, thus shift the resonant frequency of the WGMs [33].…”

“…The WGMs in microcavity will have a spin along the z direction due to the spinorbit coupling of light [33][34][35]. According to our previous work, the spin will be modulated by the magnetization along z direction due to Faraday effect, thus shift the resonant frequency of the WGMs [33]. When applying a magnetic field parallel to the resonator equator, the microwave excites the magnon mode in microcavity by an antenna and causes the procession of the magnetization in microcavity.…”

Quantum measurement with recycled photons

“…A short optical pulse having state of polarization (SOP) |p i is injected into port a1 of an optical coupler (OC). A Ferrimagnetic sphere resonator (FSR) [21,22] is integrated into the fiber loop of the FOLM near port b1 of the OC. Magneto-optic (MO) coupling [23,24] between the optical pulse and the FSR gives rise to both the Faraday-Voigt effect, which accounts for the change in the optical SOP, and the inverse Faraday effect (IFE) [25][26][27][28][29][30][31][32][33], which accounts for the optically-induced change in the FSR state of magnetization (SOM).…”

Single-photon non-reciprocity with an integrated magneto-optical isolator

“…Many non-reciprocal devices have been reported in bulk structures [11,12], and nanostructures [13,14] and are widely used in commercial optical fibers. Recently, integrated optical isolators based on magneto-optical effects [15][16][17][18], nonlinear photonic effects [19][20][21] and spatio-temporal modulation [22][23][24] have also been reported.…”