Сверхбыстрая плазмоника и магнитоплазмоника

Surface plasmon-polaritons (SPPs) is a collective oscillation of light and electrons that propagate at the boundary between metal and dielectric. The lifetime of such excitations can vary from few femtoseconds till picoseconds in the optical range of spectrum. Since the development of femtosecond lasers became possible to study and to use this ultrafast processes in devices and applications. 

Ultrafast Laser Pulse Shaping by Plasmonic Crystals
In our group, controllable reshaping of a femtosecond laser pulse reflected from a plasmonic crystal based on 1D polymer grating with period of 750 nm covered by 50 nm silver film. Reshaping of fs-pulses reflected from such plasmonic crystal was detected by time-resolved measurements of intensity correlation functions (Fig.1). 

Fig.1 Time-resolved intensity correlation functions measurement setup. Ti:Sa — titanium-sapphire femtosecond laser. Pulse duration — 150 fs, tunable wavelength from 690 nm to 1020 nm, repetition rate of 80MHz, integral power of 1.5-3 V. Step of scanning delay line is 13 fs. BBO — nonlinear crystal. PMT — photomultiplier tube.

Various shaping options (Fig.2), namely, broadening, compression, delaying, advancing, and splitting of the pulses are revealed by spectral tuning of the pulse carrier wavelength in the vicinity of surface plasmon resonances, since such pulse modification strongly depends on the interplay between parameters of the fs-pulse and SPP resonance, for example, laser pulse duration should be comparable with the SPP relaxation time. 

Fig.2. Measured correlation functions and reconstructed pulses reflected from the 1D plasmonic crystal for carrier wavelength λ0 in the range from 722 nm to 780 nm.

Ultrafast Polarization Pulse Shaping with Plasmonic Crystals
Symmetry considerations require s- and p-polarized states to be the eigenstates of the 1D plasmonic nanostructures [2,3]: if the incident pulse is s- or p-polarized the state of polarization (SoP) of the reflected pulse remains constant. However, the evolution of the SoP inside a single pulse becomes complicated if one sends a linear combination of these states onto the plasmonic crystal (Fig.3). Femtosecond-scale polarization state shaping is experimentally found in optical response of a plasmonic nanograting by means of time-resolved Stokes polarimetry [4]. 

Fig. 3. Schematics of the ultrafast polarization conversion with plasmonic crystals.

Magnetooptical Kerr Effect in Magnetoplasmonic Crystals
Another type of materials is a magnetoplasmonic nanostructures: in our case it is a ferromagnetic film with nanoscale periodic structure. Not also the excitation of SPP is possible, but the magneto-optical Kerr effects (MOKEs) can also be detected in reflected light. It is reflection coefficient or polarization state modification when magnetic field is applied. Usually MOKE is very small, but plasmonic resonance in iron or nickel plasmonic systems can enhance it up to a 7% [5,6,7]. 
Ultrafast Magnetooptical Kerr Effect in Magnetoplasmonic Crystals
On the other hand, since the MOKE enhancements is induced by SPP, that have a limited femtosecond lifetime, then the time-dependent transverse magnetooptical Kerr effect (TMOKE) can be experimentally observed within femtosecond laser pulses. Non-trivial evolution of TMOKE is demonstrated  by means of correlation function spectroscopy within 200 fs-pulses and 45 fs-pulses reflected from 1D nickel and iron-based magnetoplasmonic crystals [8,9]. Exciting SPPs with magnetic field-dependent dispersion of ferromagnetic metals allows to control the shape of the reflected pulse (Fig.4). 
Fig. 4. Illustration of the ultrafast time-dependent TMOKE. The incident pulse shown in red is transformed into an SPP wave with the dispersion law depending on the magnetization of the sample. The influence of SPPs is stronger at later time moments. As a consequence, the reflected pulse contains different profile for different sample magnetization directions giving rise to intra-pulse time-dependent TMOKE. 



Тезисы конференций

  1. A. Yu. Frolov, P. P. Vabishchevich, M. R. Shcherbakov, T. V. Dolgova, A. A. Fedyanin
    "Femtosecond Time-Resolved Transverse Kerr Effect Measurements in Magnetoplasmonic Crystals"

    The International Conference on Coherent and Nonlinear Optics/The Lasers, Applications, and Technologies (ICONO/LAT)

  2. А.Ю.Фролов
    "Фемтосекундная динамика поперечного магнитооптического эффекта Керра, индуцированная поверхностным плазмон-поляритоном "

    XX Международная конференция студентов, аспирантов и молодых учёных «Ломоносов»



  1. M. R. Shcherbakov, P. P. Vabishchevich, A. Yu. Frolov, T. V. Dolgova, and A. A. Fedyanin
    "Femtosecond intrapulse evolution of the magneto-optic Kerr effect in magnetoplasmonic crystals"

    Physical Review B (Rapid Communications)