Jean-Pierre Vilcot

Recent advances in the development of graphene-based surface plasmon resonance (SPR) interfaces

Surface plasmon resonance (SPR) is a powerful technique for measurement of biomolecular interactions in real-time in a label-free environment. One of the most common techniques for plasmon excitation is the Kretschmann configuration, and numerous studies of ligand–analyte interactions have been performed on surfaces functionalized with a variety of biomolecules, for example DNA, RNA, glycans, proteins, and peptides. A significant limitation of SPR is that the substrate must be a thin metal film. Post-coating of the metal thin film with a thin dielectric top layer has been reported to enhance the performance of the SPR sensor, but is highly dependent on the thickness of the upper layer and its dielectric constant. Graphene is a single-atom thin planar sheet of sp2 carbon atoms perfectly arranged in a honeycomb lattice. Graphene and graphene oxide are good supports for biomolecules because of their large surface area and rich π conjugation structure, making them suitable dielectric top layers for SPR sensing. In this paper, we review some of the key issues in the development of graphene-based SPR chips. The actual challenges of using these interfaces for studying biomolecular interactions will be discussed and the first examples of the use of graphene-on-metal SPR interfaces for biological sensing will be presented.

Comparison of Gold and Silver/Gold Bimetallic Surface for Highly Sensitive Near-infrared SPR Sensor at 1550 nm

A large majority of surface plasmon resonance (SPR) sensors reported in the literature are designed to operate in the visible electromagnetic spectrum. However, the near-infrared, particularly at the telecommunications wavelength of 1550xa0nm, is also especially attractive for SPR sensing applications. In fact, SPR sensors operating in this region benefit from narrower resonance and deeper field penetration. In this paper, we report a theoretical and experimental study of an SPR sensor operating at a fixed wavelength of 1550xa0nm. The influence of the choice of metals and the interrogation methods on the sensitivity of the resulting SPR sensor is investigated. Two types of sensor chips (simple gold (Au) and bimetallic silver/Au structure) and three interrogation methods (monitoring of the position of the reflectivity minimum, the position of the centroid, and the intensity evolution of the reflectivity) are examined. We show that a refractive index resolution of 2.7u2009×u200910−6 refractive index unit can be easily obtained, and with further optimization of the measurement system, the ultimate limit of detection is expected to be even lowered. Therefore, the approach discussed here already shows a promising potential for highly sensitive SPR sensors.

Graphene-based high-performance surface plasmon resonance biosensors

Surface plasmon resonance (SPR) biosensors have become a central tool for the study of biomolecular interactions, chemical detection, and immunoassays in various fields. SPR biosensors offer unparalleled advantages such as label-free and real-time analysis with very high sensitivity. To further push the limits of SPR capabilities, novel SPR structures and approaches are being actively investigated. Here we experimentally demonstrate a graphene-based SPR biosensor. By incorporating a graphene layer to the conventional gold thin film SPR structure, its biosensing sensitivity is significantly increased. This is shown in a typical affinity biosensing experiment to measure the real-time binding kinetics of biotin-streptavidin. In addition to higher sensitivity, we also obtain a much higher signal-to-noise ratio without the slightest modification of the usual measurement setup. This implies that a considerably lower limit of detection can be made possible with the novel structure. Moreover, our graphene-based SPR biosensors do not require sophisticated surface functionalization schemes as in conventional SPR in order to function. Previous reports have also suggested that graphene might effectively prevent non-specific binding of biomolecules on the sensor surface. With relatively simple fabrication methods and large scalability, these combined distinctive advantages can enable future generation of high-performance SPR biosensors.

InP photodetectors for millimeter-wave applications

We analyze waveguide InP photodetectors for millimeter wave applications. We start with the PIN waveguide photodetector pointing out key problems like optical coupling, microwave access and maximum available power. To benefit form an internal gain we introduce the waveguide InP heterojunction phototransistor showing its ability to operate up to 60 GHz.

Edge-coupled InGaAs/InP phototransistors for microwave radio fibre links

Currently, several ways are investigated concerning pico-cellular systems. Although optical feeding of base stations is involved, there are a lot of microwave signal transmission or generation schemes. Depending on the used scheme, the receiver will behave differently, either as a pure optoelectronic transceiver (microwave transmission) either as a non-linear optoelectronic system (optical microwave generation, optical locking of microwave oscillator, ...). In these fields, we present the work that we did on promising devices, i.e. InP/InGaAs edge-coupled heterojunction phototransistors in twoand three-terminal configuration. Three parts of this paper report modelling tools, device technology and characterization. Modelling tools include optical as well as optoelectronic modelling. A brief description of technological work follows. The characterization is carried out in terms of static response, frequency response and non-linear behaviour.

Simple Technological Process for the Fabrication of Optical III-V Nanowires Integrated into a Benzocyclobutene Matrix

Our research interest is the fabrication of nanometer scale waveguides for nanophotonic applications. The use of III-V materials is appropriate for waveguides operating at telecom wavelength. That is the reason why we propose a simple wafer bonding processing technique to embed an InP nanowire into a polymer matrix creating so high index contrast waveguides.

Fabrication and characterization of laterally coupled lasers

Twin stripes laser diodes emitting at 1.3 micrometers are presented. The InP based devices were fabricated using a GaInAsP based quantum well structure. The technological processes included wet etching and photolithography that allowed a good control of the heights of the laser. The top electrodes were obtained by e-beam lithography giving sufficient resolution to allow the fabrication of twin stripe lasers with an inter ridge space from 1 to 10 microns. The wet etch solutions were H3PO4/H2O2/H2O for the top GaInAs layer and H3PO4/HCL for the InP layer, the first has the advantage of being selective on InP. The final top electrodes were deposited also by e-beam lithography over a BCB insulating layer. The final laser chips showed to be effective in power (8 mW per stripe) and had a typical threshold of 40 mA. Optical and electrical coupling were investigated and showed that both were present in the lasers. The electrical coupling phenomena results in the modification of the slope and the threshold of the P(I) function when the second laser is biased while the optical coupling is demonstrated by a coupling of light in the waveguide of the second laser (shorted) while the first one is biased.

Impact of the firing step on Al2O3 passivation on p-type Czochralski Si wafers: Electrical and chemical approaches

The development of an efficient surface passivation is a key feature of silicon solar cells towards the improvement of €/W ratio. An Al2O3 layer coated by plasma-enhanced atomic layer deposition has proven its efficiency to increase the minority carrier lifetime on p-type silicon. However, the firing step, which is a common part of the manufacturing process that includes metallic pastes for screen-printed contacts, ruins this passivation effect. On the basis of photoelectric, electric, and chemical experimental studies, a correlation is provided in this paper between the different microscopic and macroscopic behaviors that govern the passivation process. To show this correlation, photoconductance decay measurements have been carried out to determine minority carrier lifetime. Following which, the capacitance–voltage measurement results are used to extract electrical parameters, namely, the densities of interface defects and effective charges. In addition, complementing secondary ion mass spectrometry (SIMS) experiments revealed the different chemical species that can be relevant for the explanation of passivation quality and macroscopic electrical measurements.

High-efficiency high-speed (60-GHz) InGaAsP multimode waveguide photodetectors

The use of optical fibers to route microwave Imillimetre-wave signals is expected to bring many new applications and so to play an increasing role in all the telecommunication networks over the next decades [1 ,2]

InP photodetectors for millimeter wave applications based on edge- coupled heterojunction phototransistors

In this paper, we present first experimental results obtained on two 1 and three terminal edge-coupled InP/InGaAs heterojunction phototransistors showing that these devices seem very promising for microwave and millimeter wave applications.