We demonstrate that the broadband nonlinear optical response of graphene can be resonantly enhanced by more than an order of magnitude through hybridization with a plasmonic metamaterial,while retaining an ultrafast nonlinear response time of ~1 ps. Transmission modulation close to ~1% is seen at a pump uence of ~0.03 mJ/cm^2 at the wavelength of ~1600 nm. This approach allows to engineer and enhance graphene's nonlinearity within a broad wavelength range enabling applications in optical switching, mode-locking and pulse shaping.Comment: The following article has been submitted to Applied Physics Letters. After it is published, it will be found at http://apl.aip.org

Generating, controlling and sensing strong magnetic fields at ever shorter time and length scales is important for both fundamental solid-state physics and technological applications such as magnetic data recording. Here, we propose a scheme for producing strong ultrashort magnetic pulses localized at the nanoscale. We show that a bimetallic nanoring illuminated by femtosecond laser pulses responds with transient thermoelectric currents of picosecond duration, which in turn induce Tesla-scale magnetic fields in the ring cavity. Our method provides a practical way of generating intense nanoscale magnetic fields with great potential for materials characterization, terahertz radiation generation and data storage applications.

Abstract:We demonstrate resonant Faraday polarization rotation in plasmonic arrays of bimetallic nano-ring resonators consisting of Au and Ni sections. This metamaterial design allows the optimization of the trade-off between the enhancement of magneto-optical effects and plasmonic dissipation. Nickel sections corresponding to as little as ~6% of the total surface of the metamaterial result in magneto-optically induced polarization rotation equal to that of a continuous nickel film. Such bimetallic metamaterials can be used in compact magnetic sensors, active plasmonic components, and integrated photonic circuits.

Abstract:We report for the first time an order of magnitude enhancement of Kerr rotation in hybrid plasmonic/ferromagnetic metamaterial resonators. Our results pave the way towards magnetically controlled metamaterials and integrated magneto-plasmonics. Interfacing plasmonic and magneto-optical materials has recently emerged as a promising approach towards active nanoscale optical elements with significant technological implications: optical isolators, modulators, data storage, sensing, imaging, therapy. Such hybrid systems combine the strong local fields at the plasmonic resonance with the magneto-optical response of ferromagnetic layers leading to magnetic control of the plasmonic response or vice-versa [1,2]. Here we demonstrate direct integration of magneto-optical materials in metamaterial resonators leading to an order of magnitude enhancement of the polar magneto-optical Kerr effect (MOKE).The system under study is a periodic array of bi-metallic Au/Ni plasmonic ring resonators, where the gold part provides a strong plasmonic response, while the nickel section is responsible for the magneto-optical effects. Taking into account the high losses of Ni which damp the plasmonic response of the resonators, as well as current manufacturing and measuring limitations, we fix the composition of the rings to ¾ Au and ¼ Ni (see Fig. 1a). The sample was fabricated by a multi-step procedure comprising e-beam lithography, film evaporation, and lift-off processes. The manufactured sample consists of bi-metallic rings with a mean diameter of 200 nm and a cross-section of 50x50 nm 2 . The unit cell is 400x400 nm 2 , while the overall size of the array is 100x100 µm 2 . Polarization azimuth rotation spectra due to the polar magneto-optical Kerr effect in the presence of a BDC=200 mT external magnetic field. Blue points correspond to a 50 nm thick Ni film and red to the bimetallic metamaterial array. Lines serve as guides for the eye. Inset: Numerically simulated electric field map of the metamaterial unit cell at resonance.

Frequency selective surfaces are very well known and have been investigated in detail. Here we for the first time introduce the concept of a wavevector selective surface and demonstrate it experimentally.