Plasmonic crystals for ultrafast nanophotonics: Optical switching of surface plasmon polaritons

Abstract

We demonstrate that the dispersion of surface plasmon polaritons in a periodically perforated gold film can be efficiently manipulated by femtosecond laser pulses with the wavelengths far from the intrinsic resonances of gold. Using a time-and frequency-resolved pump-probe technique we observe shifting of the plasmon polariton resonances with response times from 200 to 800 fs depending on the probe photon energy, through which we obtain comprehensive insight into the electron dynamics in gold. We show that Wood anomalies in the optical spectra provide pronounced resonances in differential transmission and reflection with magnitudes up to 3 % for moderate pump fluences of 0.5 mJ/cm 2 .PACS numbers: 73.20.Mf, 78.66.Bz, 78.67.Pt Nowadays plasmonics attracts much research interest in nanophotonics inspiring scientists to develop a new paradigm in data processing based on nanometallic circuitry 1,2 . The key object of plasmonics is a surface plasmon polariton (SPP) -a coupled oscillation of the electromagnetic field and the electron plasma in metals 3 . Excitation of a SPP leads to significant electromagnetic energy localization near the metal-dielectric interface, thereby enhancing nonlinear effects and light-matter interaction. Current state-of-the-art in telecommunications requires plasmonics to be active, i.e. a possibility for control by means of an external stimulus must be provided on the order of a few nanoseconds or shorter 4 .One of the approaches satisfying the strict criteria is magnetoplasmonics employing the influence of an external magnetic field on the SPP propagation constant 5,6 . While the modulation efficiency in magnetoplasmonic structures may be as large as tens of percent the operation rate is limited by the magnetization dynamics occurring on the nanoseconds timescale. Transient changes in the optical properties of plasmonic structures can be also achieved via application of intense femtosecond laser pulses 4,7-14 . Here, the real and imaginary parts of the dielectric constant of a metal change in the matter of several hundreds of femtoseconds 15-17 . Since the propagation constant of SPPs is determined by the permittivity of metal and dielectric this opens new horizons for ultrafast control of SPPs. However, the high reflectivity of smooth gold surfaces prevents most of the incident electromagnetic energy from absorption in the metal. Here, SPPs can be exploited to provide electromagnetic energy localization near the metal-dielectric interface and consequently to increase the energy absorption in gold 18,19 .Recently the optical response of plasmonic crystals with periodically perforated gold or perforated dielectric on top of gold was investigated using a two-color pumpprobe technique with the pump photon energy far from the SPP resonances 11,12 . It was demonstrated that the differential reflectivity of the probe beam tuned in resonance with a SPP can be modulated up to 10 % on a sub-picosecond timescale. Large values of the modulation parameter were accomplished by using intense laser pu...

Ultrafast Dynamics of Surface Plasmons in InAs by Time-Resolved Infrared Nanospectroscopy

“…35,36 However, this time constant in InAs is a consequence of photoexcitation far above the Γ-point with subsequent carrier relaxation to the Γ-minimum, a process that can be accelerated by injecting electrons closer to the conduction band minimum via lower photon energies. A longer plasmon lifetime in InAs of ∼60 ps compared to graphene and most metal-based schemes might prove advantageous in plasmonic circuits requiring longer propagation lengths or interaction times.…”

“…For comparison, a fluence of 40 μJ/cm 2 induced a 4% plasmon modulation in graphene, another material with exceptional mid-IR plasmon properties. 11 Metal-based structures for near-IR plasmonics require at least an order of magnitude higher fluence for changes in the few percent range 35,36 and up to ∼20% when exploiting the light-induced metallic phase of VO 2 nanoparticles. 37 Similar few percent modulations at mJ/cm 2 fluence were observed in semiconductor structures for near-IR 38 or for localized plasmon modes at terahertz frequencies.…”

Terahertz dynamics of lattice vibrations in Au/CdTe plasmonic crystals: Photoinduced segregation of Te and enhancement of optical response

“…Therefore, differential reflection of light may be significantly enhanced in the vicinity of SPP resonances [4][5][6][7][8]. The role of plasmon resonances in the optical response mediated by coherent phonon oscillations has been recently studied using femtosecond pumpprobe techniques.…”

“…Based on these principles, surface plasmon resonant sensors for the detection of chemical and biological species are developed [3]. In addition, one can use an external stimulus such as optical excitation [4][5][6][7][8], acoustic waves [9][10][11][12] and external magnetic fields [13][14][15][16] in order to influence the dielectric function of metal and/or dielectric and subsequently to control the SPP propagation constant. Therefore, SPPs are well suited for applications in optoelectronic devices where high sensitivities * lars.kreilkamp@tu-dortmund.de and efficient optical excitation at the nanoscale are essential [8].…”

Formation of plasmon pulses in the cooperative decay of excitons of quantum dots near a metal surface

“…The spectra and envelope shape of the SPP pulse can be recorded by performing the inverse transformation of surface waves to an optical signal on a metal grating [29]. Note that a noticeable change in the permittivity of a metal due to optical excitation of electrons is observed at the energy density on the order of 0.5 mJ/cm 2 [64]. This allows one to realize pure plasmon nonlinearities [29] and perform direct signal-pump experiments with surface plasmon-polaritons.…”