Repository logo

Scholarly Works - Physics - NanoPhotonics


Recent Submissions

Now showing 1 - 3 of 3
  • ItemOpen AccessAccepted version Peer-reviewed
    Effect of stray fields on Rydberg states in hollow-core PCF probed by higher-order modes.
    (The Optical Society, 2017-09-01) Epple, G; Joly, NY; Euser, TG; St J Russell, P; Löw, R; Euser, Tijmen [0000-0002-8305-9598]
    The spectroscopy of atomic gases confined in hollow-core photonic crystal fiber (HC-PCF) provides optimal atom-light coupling beyond the diffraction limit, which is desirable for various applications such as sensing, referencing, and nonlinear optics. Recently, coherent spectroscopy was carried out on highly excited Rydberg states at room temperature in a gas-filled HC-PCF. The large polarizability of the Rydberg states made it possible to detect weak electric fields inside the fiber. In this Letter, we show that by combining highly excited Rydberg states with higher-order optical modes, we can gain insight into the distribution and underlying effects of these electric fields. Comparisons between experimental findings and simulations indicate that the fields are caused by the dipole moments of atoms adsorbed on the hollow-core wall. Knowing the origin of the electric fields is an important step towards suppressing them in future HC-PCF experiments. Furthermore, a better understanding of the influence of adatoms will be advantageous for optimizing electric-field-sensitive experiments carried out in the vicinity of nearby surfaces.
  • ItemOpen AccessPublished version Peer-reviewed
    Plasmonic tunnel junctions for single-molecule redox chemistry
    (Springer Nature, 2017-10-20) de Nijs, B; Benz, F; Barrow, SJ; Sigle, DO; Chikkaraddy, R; Palma, A; Carnegie, C; Kamp, M; Sundararaman, R; Narang, P; Scherman, OA; Baumberg, JJ; Chikkaraddy, Rohit [0000-0002-3840-4188]; Kamp, Marlous [0000-0003-4915-1312]; Scherman, Oren [0000-0001-8032-7166]; Baumberg, Jeremy [0000-0002-9606-9488]
    Nanoparticles attached just above a flat metallic surface can trap optical fields in the nanoscale gap. This enables local spectroscopy of a few molecules within each coupled plasmonic hotspot, with near thousand-fold enhancement of the incident fields. As a result of non-radiative relaxation pathways, the plasmons in such sub-nanometre cavities generate hot charge carriers, which can catalyse chemical reactions or induce redox processes in molecules located within the plasmonic hotspots. Here, surface-enhanced Raman spectroscopy allows us to track these hot-electron-induced chemical reduction processes in a series of different aromatic molecules. We demonstrate that by increasing the tunnelling barrier height and the dephasing strength, a transition from coherent to hopping electron transport occurs, enabling observation of redox processes in real time at the single-molecule level.
  • ItemOpen Access
    Molecules in the mirror: how SERS backgrounds arise from the quantum method of images.
    (Royal Society of Chemistry (RSC), 2014-04-14) Barnett, Stephen M; Harris, Nadine; Baumberg, Jeremy J; Baumberg, Jeremy [0000-0002-9606-9488]
    The Raman coupling of light to molecular vibrations is strongly modified when they are placed near a plasmonic metal surface, with the appearance of a strong broad continuum background in addition to the normal surface-enhanced Raman scattering (SERS) peaks. Using a quantum method of images approach, we produce a simple but quantitative explanation of the inevitable presence of the background, due to the resistive damping of the image molecule. This model thus suggests new strategies for enhancing the SERS peak to background ratio.