Nonreciprocal plasmonics enables giant enhancement of thin-film Faraday rotation

Abstract

Light propagation is usually reciprocal. However, a static magnetic field along the propagation direction can break the time-reversal symmetry in the presence of magneto-optical materials. The Faraday effect in magneto-optical materials rotates the polarization plane of light, and when light travels backward the polarization is further rotated. This is applied in optical isolators, which are of crucial importance in optical systems. Faraday isolators are typically bulky due to the weak Faraday effect of available magneto-optical materials. The growing research endeavour in integrated optics demands thin-film Faraday rotators and enhancement of the Faraday effect. Here, we report significant enhancement of Faraday rotation by hybridizing plasmonics with magneto-optics. By fabricating plasmonic nanostructures on laser-deposited magneto-optical thin films, Faraday rotation is enhanced by one order of magnitude in our experiment, while high transparency is maintained. We elucidate the enhanced Faraday effect by the interplay between plasmons and different photonic waveguide modes in our system.

Interaction effects on the magneto-optical response of magnetoplasmonic dimers

“…Plasmonic structures composed of a number of individual elements, for example, give rise to Fano resonance effects that induce electromagnetically induced transparency (EIT) [2][3][4][5][6][7][8]. Similar phenomena have also been found in magnetoplasmonic nanosystems [9], i.e., those sharing magnetic and plasmonic functionalities and that therefore allow a further degree of freedom, namely, the external control of the system response [10][11][12][13][14]. By an adequate design of their internal structure, it is possible to obtain configurations which provide enhanced magnetooptical (MO) activity upon plasmon resonance excitation [15][16][17][18], which allow one to probe the electromagnetic (EM) field distribution inside a metallic nanoelement [19], or which yield high MO activity and low optical losses with MO figures of merit comparable with those of garnet structures [13].…”

Tunable and switchable polarization rotation with non-reciprocal plasmonic thin films at designated wavelengths

“…46 This feature is a significant advantage over BIG, which is widely utilized both in magneto-optical devices 33,34 and concept studies. 26,36,47 BIG films are typically fabricated by pulsed laser deposition 48 followed by hightemperature annealing, which is largely restricted to homogeneous films and does not allow for the direct incorporation of other materials, such as plasmonic nanostructures, into the film. With the flexibility of physical vapor deposition, EuSe provides the possibility of fabricating more sophisticated potential future designs, including 3D geometries, where the magneto-optical and plasmonic elements are merged.…”

“…In recent years, plasmons have proved capable of enhancing a number of magneto-optical effects, 4,5,8,9,36 which demonstrates their potential for ultra-thin magneto-optical devices. Using plasmons to enhance the Faraday effect has been proposed theoretically 37,38 and demonstrated experimentally.…”

“…Using plasmons to enhance the Faraday effect has been proposed theoretically 37,38 and demonstrated experimentally. 36 The experimental demonstration suggested a hybrid plasmonic-dielectric waveguide, [39][40][41] consisting of a thin BIG film and an attached plasmonic grating, which realizes a sophisticated mechanism to enhance Faraday rotation. Here, we employ this mechanism and advance it to 220-nm-thick devices, which show five times greater polarization rotation than in previously reported experiments.…”

Optical Effects Induced by Bloch Surface Waves in One-Dimensional Photonic Crystals

“…The magnitude of these effects is small, but it can be significantly enhanced near narrow optical resonances in the structures [45][46][47][48][49][50][51]. An appropriate resonant optical state for this purpose is the Bloch surface wave in magneto-photonic crystals (MPCs).…”