In this paper we excite bound long range stripe plasmon modes with a highly focused laser beam. We demonstrate highly confined plasmons propagating along a 50 µm long silver stripe 750 nm wide and 30 nm thick. Two excitation techniques were studied: focusing the laser spot onto the waveguide end and focusing the laser spot onto a silver grating. By comparing the intensity of the out-coupling photons at the end of the stripe for both grating and end excitation we are able to show that gratings provide an increase of a factor of two in the output intensity and thus out-coupling of plasmons excited by this technique are easier to detect. Authors expect that the outcome of this paper will prove beneficial for the development of passive nano-optical devices based on stripe waveguides, by providing insight into the different excitation techniques available and the advantages of each technique.

In this paper, we modeled a quantum dot at near proximity to a gap plasmon waveguide to study the quantum dot-plasmon interactions. Assuming that the waveguide is single mode, this paper is concerned about the dependence of spontaneous emission rate of the quantum dot on waveguide dimensions such as width and height. We compare coupling efficiency of a gap waveguide with symmetric configuration and asymmetric configuration illustrating that symmetric waveguide has a better coupling efficiency to the quantum dot. We also demonstrate that optimally placed quantum dot near a symmetric waveguide with 50 nm × 50 nm cross section can capture 80% of the spontaneous emission into a guided plasmon mode.

SummaryIn this paper we report the design and experimental realisation of a novel refractive index sensor based on coupling between three nanoscale stripe waveguides. The sensor is highly compact and designed to operate at a single wavelength. We demonstrate that the sensor exhibits linear response with a resolution of 6 × 10−4 RIU (refractive index unit) for a change in relative output intensity of 1%. Authors expect that the outcome of this paper will prove beneficial in highly compact, label-free and highly sensitive refractive index analysis.

SummaryIn this paper we image the highly confined long range plasmons of a nanoscale metal stripe waveguide using quantum emitters. Plasmons were excited using a highly focused 633 nm laser beam and a specially designed grating structure to provide stronger incoupling to the desired mode. A homogeneous thin layer of quantum dots was used to image the near field intensity of the propagating plasmons on the waveguide. We observed that the photoluminescence is quenched when the QD to metal surface distance is less than 10 nm. The optimised spacer layer thickness for the stripe waveguides was found to be around 20 nm. Authors believe that the findings of this paper prove beneficial for the development of plasmonic devices utilising stripe waveguides.

Active control of plasmon propagation via coupling to Quantum Dots (QDs) is a hot topic in nano-photonic research. When a QD is excited it acts like a dipole emitter. If this excited QD is placed near a metallic waveguide structure, it can decay either radiatively into bulk electromagnetic radiation, non-radiatively into heating of the metal or, of interest to this project, into a plasmon mode (γ pl ). By altering the position of the QD it is possible to optimise the decay into the plasmon mode.In this paper we present a system with a QD placed within the vicinity of a single mode Gap Plasmon Waveguide (GPW). First, we constructed a 2D finite element modelling simulation to find γ pl using COMSOL MULTIPHYSICS for symmetric GPW structures with varying width (w) of the gap and distance of the QD to the waveguide surface (d). We then constructed a 3D model to calculate total rate of spontaneous emission of a QD (γ tot ) and determine spontaneous emission β factor, which is the ratio between γ pl and all possible decay channels. It is shown that the decrease in width of the gap results in much larger β factor. As the gap width decreases, fraction of modal power in the metal increases slowing down the plasmon mode resulting in an enhancement in coupling efficiency. The optimized β factor for a square metallic slot waveguide is estimated up to 80%.