A. N. Kalish

Plasmon-mediated magneto-optical transparency

Magnetic field control of light is among the most intriguing methods for modulation of light intensity and polarization on sub-nanosecond timescales. The implementation in nanostructured hybrid materials provides a remarkable increase of magneto-optical effects. However, so far only the enhancement of already known effects has been demonstrated in such materials. Here we postulate a novel magneto-optical phenomenon that originates solely from suitably designed nanostructured metal-dielectric material, the so-called magneto-plasmonic crystal. In this material, an incident light excites coupled plasmonic oscillations and a waveguide mode. An in-plane magnetic field allows excitation of an orthogonally polarized waveguide mode that modifies optical spectrum of the magneto-plasmonic crystal and increases its transparency. The experimentally achieved light intensity modulation reaches 24%. As the effect can potentially exceed 100%, it may have great importance for applied nanophotonics. Further, the effect allows manipulating and exciting waveguide modes by a magnetic field and light of proper polarization.

Tuning of the transverse magneto-optical Kerr effect in magneto-plasmonic crystals

The spectral properties of the transverse magneto-optical Kerr effect (TMOKE) in periodic metal-dielectric hybrid structures are studied, in particular with respect to the achievable magnitude. It is shown that the TMOKE is sensitive to the magneto-optical activity of the bismuth-substituted rare-earth iron garnet, which is used as a dielectric material in the investigated structures. For samples with larger Bi substitution level and, consequently, larger gyration

Giant transversal Kerr effect in magneto-plasmonic heterostructures: The scattering-matrix method

The magneto-optical intensity effect (transversal Kerr effect) in a metal-dielectric periodic heterostructure that consists of a metallic grating formed by subwavelength slits and a dielectric substrate magnetized along the slits is shown to be resonantly enhanced by several tens of times in the excitation region of structure eigenmodes—surface plasmon polaritons and Fabry-Perot modes. The Fourier modal and scattering-matrix methods adapted to the case of gyrotropic periodic media have been used. The resonant enhancement of the intensity effect is attributable to the phenomenon of magneto-optical nonreciprocity.

Fabry–Perot plasmonic structures for nanophotonics

It is demonstrated that the presence of the metal on the walls of dielectric grating slits opens new possibilities for tailoring optical properties of metal–dielectric plasmonic gratings. In particular, a new kind of metal-thickness-sensitive resonances appear due to the excitation of the Fabry–Perot plasmonic modes in the horizontal cavity formed inside the slits by vertical metalized walls. It makes the considered plasmonic structures of great interest for applications where the concentration of the electromagnetic energy is vital. Moreover, transmission peaks related to the Fabry–Perot modes inside the slits etched in the dielectric part exhibit significant enhancement and blueshift as the thickness of the metal on the slit walls increases.

Transformation of mode polarization in gyrotropic plasmonic waveguides

We analyze the gyration impact on the mode polarization in plasmonic waveguides containing dielectrics with natural optical activity, or gyration induced by magnetization in the polar configuration or the longitudinal configuration. It has been found that the gyration mostly affects the mode polarization that acquires additional optical field components proportional to the gyration coefficient, whereas the mode dispersion remains almost unchanged. Moreover, if the gyration coefficient is rather large, then the mode loses its localization. The polarization transformation can be two orders of magnitude stronger for structures with a thin metal film than that for the solitary interface. The polarization transformation of the plasmonic modes was demonstrated experimentally via measuring optical transmittance through a layered magnetoplasmonic structure. The resonance in the transmittance spectrum corresponding to the excitation of modes of the polarization orthogonal to that of incident light was observed. The polarization transformation is enhanced if the TM and TE modes are excited simultaneously. The described effect can be applied in sensors, plasmonic circuitry, and plasmonic-based light modulators.

Effect of oblique light incidence on magnetooptical properties of one-dimensional photonic crystals

We have investigated the magnetooptical properties of one-dimensional magnetic photonic crystals for the case of oblique light incidence. We developed a theoretical model based on the transfer matrix approach. We found several new effects such as transmittance resonance peak shift versus external magnetic field and the Faraday effect dependence on the incidence angle. We discuss several possible one-dimensional magnetic photonic crystals applications for the optical devices.

Hybrid structures of magnetic semiconductors and plasmonic crystals: a novel concept for magneto-optical devices [Invited]

We propose here to combine magnetic semiconductors and plasmonic crystals to obtain a new class of devices, in which magneto-optical effects are dramatically enhanced. So far we have studied the two building blocks separately, and we demonstrate here features of these systems that make them appealing for combination. Namely, for magnetic semiconductors we demonstrate efficient tools for manipulating their magnetization. In particular, we show that in paramagnetic (Ga,Mn)As the magnetic ions can be oriented optically. For ferromagnetic (Ga,Mn)As an ultrafast strain pulse moves the magnetization out of its equilibrium position, inducing a subsequent precessional motion about the equilibrium orientation. For plasmonic crystals, on the other hand, we show that the magneto-optical effects are dramatically enhanced in both reflection and transmission. From combining the two systems, we expect to be able to obtain magneto-optical materials that can be controlled efficiently through manipulation of the magnetization of the magnetic semiconductor onto which the plasmonic crystal is deposited.

Magnetic control of waveguide modes of Bragg structures

We present the study of the waveguide modes of one-dimensional magnetic photonic crystals with in-plane-magnetized layers. There is a magneto-optical effect of nonreciprocity for the TM-modes propagating along the layers perpendicularly to the magnetization. Due to the non-reciprocity the phase velocity of the modes changes with magnetization reversal. Comparison of the effect in the non-magnetic photonic crystal with additional magnetic layer on top and a magnetophotonic crystal with altering magnetic layers shows that the effect is greater in the first case due to the higher asymmetry of the claddings of the magnetic layer. This effect is important for the light modulation with external magnetic field in waveguide structures and may be used for design of novel types of the magneto-optical devices, sensors of magnetic field or biosensors.

Optical properties of toroidal media

We consider optical phenomena that originate due to existence of the toroidal moment. These are nonreciprocal birefrigence and dichroism, polarization rotation and modulating of light intensity. Nanostructuring offers the possibility of these effects enhancement.

Transverse magnetic field impact on waveguide modes of photonic crystals

This Letter presents a theoretical and experimental study of waveguide modes of one-dimensional magneto-photonic crystals magnetized in the in-plane direction. It is shown that the propagation constants of the TM waveguide modes are sensitive to the transverse magnetization and the spectrum of the transverse magneto-optical Kerr effect has resonant features at mode excitation frequencies. Two types of structures are considered: a non-magnetic photonic crystal with an additional magnetic layer on top and a magneto-photonic crystal with a magnetic layer within each period. We found that the magneto-optical non-reciprocity effect is greater in the first case: it has a magnitude of δ∼10-4, while the second structure type demonstrates δ∼10-5 only, due to the higher asymmetry of the claddings of the magnetic layer. Experimental observations show resonant features in the optical and magneto-optical Kerr effect spectra. The measured dispersion properties are in good agreement with the theoretical predictions. An amplitude of light intensity modulation of up to 2.5% was observed for waveguide mode excitation within the magnetic top layer of the non-magnetic photonic crystal structure. The presented theoretical approach may be utilized for the design of magneto-optical sensors and modulators requiring pre-determined spectral features.