Polina P. Vabishchevich

Ultrafast All-Optical Switching with Magnetic Resonances in Nonlinear Dielectric Nanostructures

We demonstrate experimentally ultrafast all-optical switching in subwavelength nonlinear dielectric nanostructures exhibiting localized magnetic Mie resonances. We employ amorphous silicon nanodisks to achieve strong self-modulation of femtosecond pulses with a depth of 60% at picojoule-per-disk pump energies. In the pump-probe measurements, we reveal that switching in the nanodisks can be governed by pulse-limited 65 fs-long two-photon absorption being enhanced by a factor of 80 with respect to the unstructured silicon film. We also show that undesirable free-carrier effects can be suppressed by a proper spectral positioning of the magnetic resonance, making such a structure the fastest all-optical switch operating at the nanoscale.

Ultrafast all-optical tuning of direct-gap semiconductor metasurfaces

Optical metasurfaces are regular quasi-planar nanopatterns that can apply diverse spatial and spectral transformations to light waves. However, metasurfaces are no longer adjustable after fabrication, and a critical challenge is to realise a technique of tuning their optical properties that is both fast and efficient. We experimentally realise an ultrafast tunable metasurface consisting of subwavelength gallium arsenide nanoparticles supporting Mie-type resonances in the near infrared. Using transient reflectance spectroscopy, we demonstrate a picosecond-scale absolute reflectance modulation of up to 0.35 at the magnetic dipole resonance of the metasurfaces and a spectral shift of the resonance by 30 nm, both achieved at unprecedentedly low pump fluences of less than 400 μJ cm–2. Our findings thereby enable a versatile tool for ultrafast and efficient control of light using light.Metasurfaces are not adjustable after fabrication, and a critical challenge is to realise a technique of tuning their optical properties that is both fast and efficient. Here, Shcherbakov et al. realise an ultrafast tunable metasurface with picosecond-scale large absolute reflectance modulation at low pump fluences.

Ultrafast polarization shaping with Fano plasmonic crystals.

Femtosecond-scale polarization state shaping is experimentally found in optical response of a plasmonic nanograting by means of time-resolved Stokes polarimetry. Simultaneous measurements of the Stokes parameters as a function of time reveal a remarkable alteration of the polarization state inside a single femtosecond pulse reflected from a plasmonic crystal due to the excitation of time-delayed polarization-sensitive surface plasmons with a highly birefringent Fano-type spectral profile. Time-dependent depolarization, indicating the sub-130-femtosecond polarization change inside the pulse, is experimentally found and described within an analytical model which predicts the fivefold enhancement of the polarization conversion effect with the use of a narrower time gate.

Femtosecond relaxation dynamics of surface plasmon-polaritons in the vicinity of fano-type resonance

Temporal modification of femtosecond laser pulses reflected from planar periodic metal nanostructures with resonant excitation of surface plasmon-polaritons is experimentally studied. Spectral time-resolved measurements of the second-order cross-correlation function performed with the pulse duration comparable with the surface plasmon-polariton relaxation time (about 100 fs) show the strong spectral dependence of the envelope of the reflected femtosecond pulse described by Fano-resonance parameters.

Plasmonic enhancement of linear birefringence and linear dichroism in anisotropic optical metamaterials

The resonant behavior of linear birefringence and linear dichroism spectra is found in anisotropic optical metamaterials made of noble metal thin films with stripes and rectangular hole nanoapertures forming one- or two-dimensional subwavelength gratings. Differences in effective refractive index and extinction coefficient for linearly polarized eigenstates are increased in spectral range of resonances of local and surface plasmon-polaritons at the normal incidence and reach the values of Δn ≃ 2.5 and Δκ ≃ 2.75, respectively.

Magnetic field-controlled femtosecond pulse shaping by magnetoplasmonic crystals

Femtosecond-scale magnetic field-controlled shaping of 200 fs laser pulses reflected from a one-dimensional magnetoplasmonic crystal is experimentally demonstrated. Magnetic field-induced modification of the pulse shape is revealed by measuring the second-order intensity correlation function (CF) of femtosecond pulses reflected from the sample. The sign of the magnetic contribution to the CF is reversed within the pulse. Such temporal shaping of the pulses is attributed to modification of the Fano-type surface plasmon spectral response function under magnetization of the sample in the Voigt configuration.

Femtosecond Pulse Shaping with Plasmonic Crystals

The temporal shaping of femtosecond laser pulses reflected from a one-dimensional plasmonic crystal using a commercially available polymer grating coated with a silver film is experimentally demonstrated by timeresolved measurements of the intensity correlation function. Shaping is achieved by the excitation of surface plasmon-polaritons with a lifetime comparable to the 130 fs laser pulse duration. The variety of data obtained demonstrate the flexible shaping of fs-pulses by delaying, advancing, splitting, broadening, compressing, and changing the topological properties of the pulse with the plasmonic crystals under study.

Femtosecond intrapulse evolution of the magneto-optic Kerr effect in magnetoplasmonic crystals

Samsung R&D Institute Russia, Moscow, Russia(Dated: July 23, 2014)In magnetoplasmonics, it is possible to tailor the magneto-optical properties of nanostructuresby exciting surface plasmon polaritons (SPPs). Thus far, magnetoplasmonic effects have beenconsidered static. Here, we describe ultrafast manifestations of magnetoplasmonics by observingthe non-trivial evolution of the transverse magneto-optic Kerr effect within 45-fs pulses reflectedfrom an iron-based magnetoplasmonic crystal. The effect occurs for resonant SPP excitations,displays opposite time derivative signs for different slopes of the resonance, and is explained withthe magnetization-dependent dispersion relation of SPPs.

Plasmon induced modification of silicon nanocrystals photoluminescence in presence of gold nanostripes

We report on the results of theoretical and experimental studies of photoluminescense of silicon nanocrystals in the proximity to plasmonic modes of different types. In the studied samples, the type of plasmonic mode is determined by the filling ratio of a one-dimensional array of gold stripes which covers the thin film with silicon nanocrystals on a quartz substrate. We analyze the extinction, photoluminesce spectra and decay kinetics of silicon nanocrystals and show that the incident and emitted light is coupled to the corresponding plasmonic mode. We demonstrate the modification of the extinction and photoluminesce spectra under the transition from wide to narrow gold stripes. The experimental extinction and photoluminescense spectra are in good agreement with theoretical calculations performed by the rigorous coupled wave analysis. We study the contribution of individual silicon nanocrystals to the overall photoluminescense intensity, depending on their spacial position inside the structure.

An all-dielectric metasurface as a broadband optical frequency mixer.

A frequency mixer is a nonlinear device that combines electromagnetic waves to create waves at new frequencies. Mixers are ubiquitous components in modern radio-frequency technology and microwave signal processing. The development of versatile frequency mixers for optical frequencies remains challenging: such devices generally rely on weak nonlinear optical processes and, thus, must satisfy phase-matching conditions. Here we utilize a GaAs-based dielectric metasurface to demonstrate an optical frequency mixer that concurrently generates eleven new frequencies spanning the ultraviolet to near-infrared. The even and odd order nonlinearities of GaAs enable our observation of second-harmonic, third-harmonic, and fourth-harmonic generation, sum-frequency generation, two-photon absorption-induced photoluminescence, four-wave mixing and six-wave mixing. The simultaneous occurrence of these seven nonlinear processes is assisted by the combined effects of strong intrinsic material nonlinearities, enhanced electromagnetic fields, and relaxed phase-matching requirements. Such ultracompact optical mixers may enable a plethora of applications in biology, chemistry, sensing, communications, and quantum optics.Frequency mixers are hard to achieve at optical frequencies because it is difficult to meet different phase-matching conditions. Here, the authors show that GaAs metasurfaces can mix laser beams to generate eleven new wavelengths through different nonlinear optical processes occurring simultaneously.