31 research outputs found
Micromagnetic view on ultrafast magnon generation by femtosecond spin current pulses
In this Article we discuss a micromagnetic modelling approach to describe the
ultrafast spin-transfer torque excitation of coherent and incoherent magnons on
the nanoscale. Implementing the action of a femtosecond spin current pulse
entering an orthogonally magnetized thin ferromagnetic film, we reproduce
recent experimental results and reveal the factors responsible for the unequal
excitation efficiency of various spin waves. Our findings are in an excellent
agreement with the results of an analytical description of spin-wave excitation
based on classical kinetic equations. Furthermore, we suggest an experimental
design allowing for the excitation of laterally propagating spin waves beyond
the optical diffraction limit. Our findings demonstrate that the classical
micromagnetic picture retains its predictive and interpretative power on
femtosecond temporal and nanometer spatial scales
Second Harmonic Generation from Critically Coupled Surface Phonon Polaritons
Mid-infrared nanophotonics can be realized using sub-diffractional light
localization and field enhancement with surface phonon polaritons in polar
dielectric materials. We experimentally demonstrate second harmonic generation
due to the optical field enhancement from critically coupled surface phonon
polaritons at the 6H-SiC-air interface, employing an infrared free-electron
laser for intense, tunable, and narrowband mid-infrared excitation. Critical
coupling to the surface polaritons is achieved using a prism in the Otto
geometry with adjustable width of the air gap, providing full control over the
excitation conditions along the polariton dispersion. The calculated
reflectivity and second harmonic spectra reproduce the full experimental data
set with high accuracy, allowing for a quantification of the optical field
enhancement. We also reveal the mechanism for low out-coupling efficiency of
the second harmonic light in the Otto geometry. Perspectives on surface phonon
polariton-based nonlinear sensing and nonlinear waveguide coupling are
discussed
Nonlinear surface magneto-plasmonics in Kretschmann multilayers
The nonlinear magneto-plasmonics aims to utilize plasmonic excitations to
control the mechanisms and taylor the efficiencies of the non-linear light
frequency conversion at the nanoscale. We investigate the mechanisms of
magnetic second harmonic generation in hybrid gold-cobalt-silver multilayer
structures, which support propagating surface plasmon polaritons at both
fundamental and second harmonic frequencies. Using magneto-optical spectroscopy
in Kretschmann geometry, we show that the huge magneto-optical modulation of
the second harmonic intensity is dominated by the excitation of surface plasmon
polaritons at the second harmonic frequency, as shown by tuning the optical
wavelength over the spectral region of strong plasmonic dispersion. Our
proof-of-principle experiment highlights bright prospects of nonlinear
magneto-plasmonics and contributes to the general understanding of the
nonlinear optics of magnetic surfaces and interfaces.Comment: Main Manuscript: 5 pages, 3 figures. Supplementary Information: 10
pages, 7 figure
Surface plasmon-mediated nanoscale localization of laser-driven sub-THz spin dynamics in magnetic dielectrics
Ultrafast all-optical control of spins with femtosecond laser pulses is one
of the hot topics at the crossroads of photonics and magnetism with a direct
impact on future magnetic recording. Unveiling light-assisted recording
mechanisms for an increase of the bit density beyond the diffraction limit
without excessive heating of the recording medium is an open challenge. Here we
show that surface plasmon-polaritons in hybrid metal-dielectric structures can
provide spatial confinement of the inverse Faraday effect, mediating the
excitation of localized coherent spin precession with 0.41 THz frequency. We
demonstrate a two orders of magnitude enhancement of the excitation efficiency
at the surface plasmon resonance within the 100 nm layer in dielectric garnet.
Our findings broaden the horizons of ultrafast spin-plasmonics and open
pathways towards non-thermal opto-magnetic recording at the nano-scale
Nonlinear acousto-magneto-plasmonics
We review the recent progress in experimental and theoretical research of
interactions between the acoustic, magnetic and plasmonic transients in hybrid
metal-ferromagnet multilayer structures excited by ultrashort laser pulses. The
main focus is on understanding the nonlinear aspects of the acoustic dynamics
in materials as well as the peculiarities in the nonlinear optical and
magneto-optical response. For example, the nonlinear optical detection is
illustrated in details by probing the static magneto-optical second harmonic
generation in gold-cobalt-silver trilayer structures in Kretschmann geometry.
Furthermore, we show experimentally how the nonlinear reshaping of giant
ultrashort acoustic pulses propagating in gold can be quantified by
time-resolved plasmonic interferometry and how these ultrashort optical pulses
dynamically modulate the optical nonlinearities. The effective medium
approximation for the optical properties of hybrid multilayers facilitates the
understanding of novel optical detection techniques. In the discussion we
highlight recent works on the nonlinear magneto-elastic interactions, and
strain-induced effects in semiconductor quantum dots.Comment: 30 pages, 12 figures, to be published as a Topical Review in the
Journal of Optic
Second Harmonic Generation from Phononic Epsilon-Near-Zero Berreman Modes in Ultrathin Polar Crystal Films
Immense optical field enhancement was predicted to occur for the Berreman
mode in ultrathin films at frequencies in the vicinity of epsilon near zero
(ENZ). Here, we report the first experimental proof of this prediction in the
mid-infrared by probing the resonantly enhanced second harmonic generation
(SHG) at the longitudinal optic phonon frequency from a deeply
subwavelength-thin aluminum nitride (AlN) film. Employing a transfer matrix
formalism, we show that the field enhancement is completely localized inside
the AlN layer, revealing that the observed SHG signal of the Berreman mode is
solely generated in the AlN film. Our results demonstrate that ENZ Berreman
modes in intrinsically low-loss polar dielectric crystals constitute a
promising platform for nonlinear nanophotonic applications
Nanoscale magnetophotonics
This Perspective surveys the state-of-the-art and future prospects of science
and technology employing the nanoconfined light (nanophotonics and
nanoplasmonics) in combination with magnetism. We denote this field broadly as
nanoscale magnetophotonics. We include a general introduction to the field and
describe the emerging magneto-optical effects in magnetoplasmonic and
magnetophotonic nanostructures supporting localized and propagating plasmons.
Special attention is given to magnetoplasmonic crystals with transverse
magnetization and the associated nanophotonic non-reciprocal effects, and to
magneto-optical effects in periodic arrays of nanostructures. We give also an
overview of the applications of these systems in biological and chemical
sensing, as well as in light polarization and phase control. We further review
the area of nonlinear magnetophotonics, the semiconductor spin-plasmonics, and
the general principles and applications of opto-magnetism and nano-optical
ultrafast control of magnetism and spintronics
Observation of the nonlinear Wood's anomaly on periodic arrays of nickel nanodimers
Linear and nonlinear magneto-photonic properties of periodic arrays of nickel
nanodimers are governed by the interplay of the (local) optical response of
individual nanoparticles and (non-local) diffraction phenomena, with a striking
example of Wood's anomaly. Angular and magnetic-field dependencies of the
second harmonic intensity evidence Wood's anomaly when new diffraction orders
emerge. Near-infrared spectroscopic measurements performed at different optical
wavelengths and grating constants discriminate between the linear and nonlinear
excitation mechanisms of Wood's anomalies. In the nonlinear regime the Wood's
anomaly is characterized by an order-of-magnitude larger effect in intensity
redistribution between the diffracted beams, as compared to the linear case.
The nonlinear Wood's anomaly manifests itself also in the nonlinear magnetic
contrast highlighting the prospects of nonlinear magneto-photonics.Comment: 8 pages, 6 figure