Electron-induced limitation of surface plasmon propagation in silver nanowires

Selective excitation of surface plasmon modes propagating in Ag nanowires

Surface plasmon modes propagating in metal nanowires are conveniently excited by focusing a laser beam on one extremity of the nanowire. We find that the precise positioning of the nanowire inside the focal region drastically influences the excitation efficiency of the different SPP modes sustained by the plasmonic waveguide. We demonstrate a spatially selective excitation of bound and leaky surface plasmon modes with excitation maps that strongly depend on the orientation of the incident linear polarization. We discuss this modal selection by considering the inhomogeneous distribution of the field components inside the focus. Our finding provides a way to discriminate the effective indices of the modes offering thus an increased coupling agility for future nanowire-based plasmonic architectures.

Solvothermal fabrication of thin Ag nanowires assisted with AAO

Silver nanowires were synthesized using solvothermal method assisted with AAO. AAO here is playing a role as a heterogeneous medium that can promote PVP molecules to form into one dimensional template and thus guiding the growth of Ag nanowires.

Excitation of surface plasmons from silver nanowires embedded in polymer nanofibers

We report an excitation of surface plasmons in silver nanowires (AgNWs) which were embedded in flexible polymer nanofibers. Using waveguiding excitation, surface plasmons in AgNWs were excited and propagated. By directing light of 650, 532, and 473 nm wavelengths into the nanofiber, surface plasmons in an embedded single AgNW (average diameter 400 nm, length 4.3 μm) were excited and the corresponding propagation lengths for the three wavelengths are 10.6, 7.7, and 5.1 μm. It was also found that, when a spatially incoherent white light of a halogen lamp with an excitation optical power of 80 μW was coupled into the polymer nanofiber, a surface plasmon mediated interference fringe was observed. In addition, on the basis of surface plasmon excitation, two adjacent AgNWs embedded in the polymer nanofibers were demonstrated to serve as coupled plasmonic waveguides.

Evaluating plasmonic transport in current-carrying silver nanowires

Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information support. In this context, metal nanowires are especially desirable for realizing dense routing networks. A prerequisite to operate such shared nanowire-based platform relies on our ability to electrically contact individual metal nanowires and efficiently excite surface plasmon polaritons in this information support. In this article, we describe a protocol to bring electrical terminals to chemically-synthesized silver nanowires randomly distributed on a glass substrate. The positions of the nanowire ends with respect to predefined landmarks are precisely located using standard optical transmission microscopy before encapsulation in an electron-sensitive resist. Trenches representing the electrode layout are subsequently designed by electron-beam lithography. Metal electrodes are then fabricated by thermally evaporating a Cr/Au layer followed by a chemical lift-off. The contacted silver nanowires are finally transferred to a leakage radiation microscope for surface plasmon excitation and characterization. Surface plasmons are launched in the nanowires by focusing a near infrared laser beam on a diffraction-limited spot overlapping one nanowire extremity. For sufficiently large nanowires, the surface plasmon mode leaks into the glass substrate. This leakage radiation is readily detected, imaged, and analyzed in the different conjugate planes in leakage radiation microscopy. The electrical terminals do not affect the plasmon propagation. However, a current-induced morphological deterioration of the nanowire drastically degrades the flow of surface plasmons. The combination of surface plasmon leakage radiation microscopy with a simultaneous analysis of the nanowire electrical transport characteristics reveals the intrinsic limitations of such plasmonic circuitry.