We provide the experimental research on a novel type of all-dielectric magnetic structure designed to achieve an enhanced magneto-optical response. 1D grating fabricated via etching of bismuth substituted iron garnet film supports the excitation of optical guided modes, which are highly sensitive to the external magnetic field. A unique feature of proposed structure is the synergetic combination of high transparency, tunability, high Q-factor of the resonances and superior magneto-optical response that is two orders higher in magnitude than in the non-structured smooth iron-garnet film. The considered all-dielectric magnetic garnet structures have great potential in various fields including the magneto-optical modulation of light, biosensing and magnetometry.

Currently spin waves are considered for computation and data processing as an alternative to charge currents. Generation of spin waves by ultrashort laser pulses provides several important advances with respect to conventional approaches using microwaves. In particular, focused laser spot works as a point source for spin waves and allows for directional control of spin waves and switching between their different types. For further progress in this direction it is important to manipulate with the spectrum of the optically generated spin waves. Here we tackle this problem by launching spin waves by a sequence of femtosecond laser pulses with pulse interval much shorter than the relaxation time of the magnetization oscillations. This leads to the cumulative phenomenon and allows us to generate magnons in a specific narrow range of wavenumbers. The wavelength of spin waves can be tuned from 15 μm to hundreds of microns by sweeping the external magnetic field by only 10 Oe or by slight variation of the pulse repetition rate. Our findings expand the capabilities of the optical spin pump-probe technique and provide a new method for the spin wave generation and control.

Ultra-thin magnetic dielectric films are of prime importance due to their applications for nanophotonics and spintronics. Here, we propose an efficient method for the magneto-optical investigation of ultra-thin magnetic films which allows one to access their state of magnetization and magneto-optical properties. It is based on the surface-plasmon-polariton-assisted transverse magneto-optical Kerr effect (TMOKE). In our experiments, sub-100 nm-thick bismuth-substituted lutetium iron-garnet films covered with a plasmonic gold grating have been analyzed. The excitation of surface plasmon-polaritons provides resonance enhancement of TMOKE up to 0.04 and makes it easily detectable in the experiment. For films thicker than 40 nm, the TMOKE marginally depends on the film thickness. A further decrease in the film thickness diminishes TMOKE since for such thicknesses the surface plasmon-polariton field partly penetrates inside the non-magnetic substrate. Nevertheless, the TMOKE remains measurable even for few-nm-thick films, which makes this technique unique for the magneto-optical study of ultra-thin films. Particularly, the proposed method reveals that the off-diagonal components of the magnetic film permittivity tensor grow slightly with the reduction of the film thickness.

Nanostructured magneto-optical materials that sustain optical resonances provide an efficient way to control light via the magnetic field, which is of prime importance for telecommunication and sensing applications. However, their response is usually narrowband due to their resonance character. Here, we demonstrate and investigate a type of magnetoplasmonic structure, or quasicrystal, that demonstrates a unique magneto-optical response. It consists of a magnetic dielectric film covered by a thin gold layer perforated by slits, forming a Fibonacci-like binary sequence. The transverse magneto-optical Kerr effect (TMOKE) acquires controllable multiple plasmon-related resonances, resulting in a magneto-optical response over a wide frequency range. In particular, for the experimentally studied samples, the TMOKE resonances are observed in the wavelength range from $\lambda =780\mathrm{nm}$ to $\lambda =970\mathrm{nm}$. Multiband TMOKE is valuable for numerous nanophotonic applications, including optical sensing, control of light, all-optical control of magnetization, etc. TMOKE spectroscopy is also an efficient tool for investigating the peculiarities of plasmonic quasicrystals.

In previous decades, significant efforts have been devoted to increasing the magneto-optical efficiency of iron garnet materials for the miniaturization of nonreciprocal devices such as isolators and circulators. Elemental substitutions, or proper nanostructuring to benefit from optical resonances, have been pursued. However, all these approaches still require film thicknesses of at least several tens of microns to deliver useful device applications, and suffer from narrow bandwidths in the case of optical resonance effects. This paper reports on a newly discovered enhancement of the Faraday effect observed experimentally in nanoscale bismuth-substituted iron garnet films. It is shown here that this enhancement is not due to elemental substitution or compositional variations, nor is it due to photon trapping or resonance effects. Comprehensive experimental and theoretical analysis of the Faraday rotation reveals a dramatic sevenfold amplification in the magneto-optic gyrotropy within only 2 nm of the air–surface interface, corresponding to just a couple of atomic monolayers as a result of symmetry breaking at the air–film interface. This finding opens up an avenue to the application of monolayer magnetic garnets for the control of light.