A realistic fabrication and design concept for quantum gates based on single emitters integrated in plasmonic-dielectric waveguide structures.

Tremendous enhancement of light-matter interaction in plasmonic-dielectric hybrid devices allows for non-linearities at the level of single emitters and few photons, such as single photon transistors. However, constructing integrated components for such devices is technologically extremely challenging. We tackle this task by lithographically fabricating an on-chip plasmonic waveguide-structure connected to far-field in- and out-coupling ports via low-loss dielectric waveguides. We precisely describe our lithographic approach and characterize the fabricated integrated chip. We find excellent agreement with rigorous numerical simulations. Based on these findings we perform a numerical optimization and calculate concrete numbers for a plasmonic single-photon transistor.

Miniaturized Bragg-grating couplers for SiN-photonic crystal slabs.

We report on an experimental and theoretical investigation of an integrated Bragg-like grating coupler for near-vertical scattering of light from photonic crystal waveguides with an ultra-small footprint of a few lattice constants only. Using frequency-resolved measurements, we find the directional properties of the scattered radiation and prove that the coupler shows a good performance over the complete photonic bandgap. The results compare well to analytical considerations regarding 1d-scattering phenomena as well as to FDTD simulations.

Thermo-optical response of photonic crystal cavities operating in the visible spectral range.

In this paper we study thermo-optical effects in gallium phosphite photonic crystal cavities in the visible range. By measuring the shift of narrow resonances, we derive the temperature dependency of the local refractive index of gallium phosphide in an attoliter volume over a temperature range between 5 and 300 K at a wavelength of about 605 nm. Additionally, the potential of photonic crystal cavities for thermo-optical switching of visible light is investigated. As an example we demonstrate thermo-optical switching with 13 dB contrast.

Fuel cell-powered microfluidic platform for lab-on-a-chip applications.

The achievement of a higher degree of integration of components--especially micropumps and power sources--is a challenge currently being pursued to obtain portable and totally autonomous microfluidic devices. This paper presents the integration of a micro direct methanol fuel cell (µDMFC) in a microfluidic platform as a smart solution to provide both electrical and pumping power to a Lab-on-a-Chip system. In this system the electric power produced by the fuel cell is available to enable most of the functionalites required by the microfluidic chip, while the generated CO(2) from the electrochemical reaction produces a pressure capable of pumping a liquid volume through a microchannel. The control of the fuel cell operating conditions allows regulation of the flow rate of a liquid sample through a microfluidic network. The relation between sample flow rate and the current generated by the fuel cell is practically linear, achieving values in the range of 4-18 µL min(-1) while having an available power between 1-4 mW. This permits adjusting the desired flow rate for a given application by controlling the fuel cell output conditions and foresees a fully autonomous analytical Lab-on-a-Chip in which the same device would provide the electrical power to a detection module and at the same time use the CO(2) pumping action to flow the required analytes through a particular microfluidic design.

Nanoassembled plasmonic-photonic hybrid cavity for tailored light-matter coupling.

We propose and demonstrate a hybrid cavity system in which metal nanoparticles are evanescently coupled to a dielectric photonic crystal cavity using a nanoassembly method. While the metal constituents lead to strongly localized fields, optical feedback is provided by the surrounding photonic crystal structure. The combined effect of plasmonic field enhancement and high quality factor (Q approximately 900) opens new routes for the control of light-matter interaction at the nanoscale.

Controlled coupling of a single-diamond nanocrystal to a photonic crystal cavity.

We demonstrate the controlled coupling of a single diamond nanocrystal to a planar photonic crystal double-heterostructure cavity. A dip-pen deposition method and subsequent manipulation with an atomic force microscope was used to precisely position the nanocrystal on top of the cavity. The optical properties of this combined system are investigated with regard to changes in the quality factor and resonance wavelength of the cavity mode as a function of the size and relative position of the diamond nanocrystal. These studies represent an important step toward well-controlled cavity-QED experiments with single-defect centers in diamond.

Modification of visible spontaneous emission with silicon nitride photonic crystal nanocavities.

Photonic crystal (PC) nanocavities based on silicon nitride membranes are studied as tools for the manipulation of spontaneous emission in the wavelength range between 550 nm and 800 nm. We observe a strong modification of the fluorescence spectrum of dye molecules spin-cast on top of the PC, indicating an efficient coupling of the dye emission to the cavity modes. The cavity design is optimized with respect to the quality factor and values of nearly 1500 are achieved experimentally. Taking into account the small mode volume, which leads to a strong Purcell enhancement, these nanocavities enable the realization of efficient single photon sources in the visible region of the spectrum. Furthermore, their fabrication is fully compatible with existing CMOS technology, making an integration into more complex optoelectronic devices feasible.