The POCT technology involving low cost Lab-On-Chip label-free biosensing opens up an opportunity to drastically reduce the total cost of plant health and disease monitoring tools. The main requirement for a POCT tool is that it should involve relatively inexpensive equipment ensuring a sufficiently high accuracy of the plant disease early diagnostic. The principal objective of the presented work was to develop of a cost effective tool for biosensing assay, easy to use even for unskilled user. The label-free biosensing involving an optical near-field resonance phenomenon, such as Surface Plasmon Resonance (SPR) or localized surface plasmon resonance (LSPR), appears to be an appropriate approach for the above requirements. In this paper, we present a concept of multichannel biosensing platform dedicated to POCT, as well as the first proof-of-concept experimental investigations, demonstrating its practical feasibility. The instrumental platform investigated by our research group includes both disposable multichannel biochip and spectroscopic optical readout device. The proposed approach gives access to two plasmonic detection formats on the same lab-on-chip device: SPR and LSPR biosensing. In order to implement the LSPR sensing approach, our team has developed an original microfabrication method involving gold nanoparticles (Au_NPs) synthesis by pulsed laser writing. The biochip includes both microfluidic and biosensor structures formed into a single plastic slab.
We present three optical multi-channels spectrometers for the interrogation of label-free biosensors based on different kinds of transducers : resonant nanopillars (RNP), microring resonators (MRR), localized and propagative surface plasmon resonance (LSPR and SPR). Light is collected from the multi-channel biosensors (up to 12-channels) with optical fibers and is remapped to a packed straight line forming the input slit of the spectrometers. The combination of high resolution CMOS sensors and embedded signal processing makes it possible to extract the resonant wavelengths of the transducers with a precision in the range of 1-20 pm depending on the type of transducer. The performance of the three transducer / spectrometer systems has been evaluated in the framework of EU and regional projects for the monitoring of chemical pollutants found in oceanic waters (FP7 - EnviGuard), crop health monitoring (Interreg France-Wallonie-Vlaanderen - SmartBioControl/BioSens) and bioreactor monitoring (EutoTransBio - APTACHIP).
In this work, a trilayer graphene is used as a thin non dielectric spacer with a high index of refraction, between Au film
and Au NPs. Encouraged by the sharpness of the localized surface plasmon resonance LSPR induced by this system, we
performed sensitivity measurements to refractive index change in the surrounding medium of the sensor. The presence of
graphene led to both higher sensitivity and sharper full width at half maximum FWHM and thus higher figure of merit
FOM (2.8) compared to the system without graphene (2.1).
We present the design, implementation and characterization of an integrated surface plasmon resonance
biosensor chip involving diffractive optical coupling elements avoiding the need of prism coupling. The
integrated sensor chip uses the angular interrogation principle and includes two diffraction gratings and the SPR
sensing zone. The theoretical design is presented as well as the fabrication procedure. Experimental results,
using reference index fluids, are compared to theoretical predictions and prism coupling experimental results.
We believe that this architecture is perfectly suitable for low cost and reproducible SPR biochemical sensor
chips since the sensing zone can be functionalized as any other one.
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.
Marie Lesecq, Maxime Beaugeois, Sophie Maricot, Christophe Boyaval, Christiane Legrand, Marc François, Michel Muller, Francis Mollot, Mohammed Bouazaoui, Jean-Pierre Vilcot
KEYWORDS: Waveguides, Electrodes, Optical switching, Near field optics, Etching, Switches, Wave propagation, Scanning electron microscopy, Bridges, Reactive ion etching
We report on a new type of optical switch based on submicron structures and present the results obtained on the
first nanophotonics based optical switch.
First, we present results obtained on passive components that are required in an optical switch or switching
matrix: straight waveguides, bend waveguides and Y junctions. Measured propagation loss are lower than
1dB/mm for waveguides wider than 1&mgr;m. Excess bending loss is 1dB for curvature radius as small as 30&mgr;m.
Loss due to branching angle in a Y junction is 2dB for angle as wide as 20°.
Optical switch design is based on two dissymmetric DOS like active junctions; theoretical crosstalk is 28dB,
14dB for each junction. We present the technological process to realize this active component. Finally, we report
on the first characterization of a single Y junction a crosstalk of 11dB.
The paper addresses two microwave photonics functionalities based on device potentialities. The first one is
related to the specific use of a mode locked (multi-section) laser diode in the analog domain where different modulation
functions can be achieved. The second one deals with the specific design of a photodetector aiming to separately detect
multiple modulated input beams and to group the resulting photocurrents into a single one. This leads to build an
optoelectronic "add" function that can be used, for example, in microwave photonics signal processing applications such
as optical beamforming networks for phased array antennas.
A uniform Bragg grating as dispersive device of InGaAsP/InP integrated chirped pulse compressors are studied. Results of numerical analysis for the propagation of chirped ultrafast pulses are presented. The compression factor and the length of the device have been designed looking for an optimum behaviour for a monolithic implementation in a 40 GHz mode-locked diode laser.
In this work we present a new mode-locked device that can be used for millimeter-wave photonic applications. Such device presents for certain bias conditions a dual-mode behavior we have investigated for millimeter wave generation. Through the small signal analysis of the device, we have identified a resonance at the frequency separation of the longitudinal modes that has allowed us to demonstrate signal transmission at 40 GHz. The millimeter wave signal generated in detection is studied in terms of phase noise and the noise intrinsic to the emitter.
In this work we present a new mode-locked device that can be used for photonic millimetre-wave applications, and more specifically optoelectronic mixing. This device is based on a mode-locked MQW-DFB multisection laser that presents for certain bias conditions a dual longitudinal mode behavior (39.5 GHz separation) that can be used for mm-wave generation and transmission. In this work we focus on the possibility of achieving optoelectronic mixing using this new device through the injection of an intermediate frequency (IF) signal in one of the sections (absorber) while the gain section is used to mode-locked the two longitudinal modes by injecting a signal at 39.5 GHz. Demonstration of the optical up-conversion is carried out through the study of the modulation sidebands for different IF frequencies and a spurious free dynamic range (SFDR) of 65dB-HZ2/3 has been measured. Transmission of an up-converted NRZ 32Mbps PRBS signal using this device for optical mixing is also demonstrated.
In this work a study of the dependence of the coupling in laterally coupled diode lasers (LCDL) with the relative bias conditions is presented. The study is made by the analysis of the spectrally resolved near and far field optical spectrum combined with the frequency responses of these devices at different bias conditions. By the analysis of these measurements it was observed that three different operation regions appear, and are identified by the spectral phase relation between the fields emitted by each laser stripe.
We present here the design, fabrication and first measurements of integrated Bragg grating apodized filters, operating at a free-space wavelength of about 1550 nm, based on InP material line ridge waveguides. Their apodized transmission spectra are obtained by the mean of sampled grating structures.
The fabrication process by means of electron beam lithography will be described. It has been used to realize the sampled gratings which are spatially localized on the wafer.
The transmission spectrum of the filters is measured. The transmission dip is almost -30 dB over almost 0.25 nm which is in a good agreement with theoretical calculations. The suppression is better than 20dB outside a bandwidth of almost 1nm, whereas a uniform grating with the same dimensions only presents almost 10dB suppression outside the same bandwidth.
One of the most important concerns in photonic integrated circuits is the reduction of the propagation path for optical interconnections leading so to a size decrease of active and passive components such as filters or multichannel wavelength (de)multiplexers. In this aim, it is necessary to use monomode optical waveguides with a high optical confinement via a strong index contrast. So the structures reported here consist in 300 nm-wide GaAs nano-wires and nano-gratings inserted in a polymer matrix. The technological process we present hereby allows fabricating symmetric waveguides with square cross-section.
We present theoretical study, technological realization and characterization of fabricated devices: TIR switches, electro-optical directional coupler switches and DOS switches because of their good linearity, low noise figure and short switching time which make them particularly suitable for microwave applications.
A novel multi-longitudinal-mode rate-equations description of the Fabry-Perot type semiconductor laser is presented. The model includes gain dynamics among the longitudinal modes due to e.g. spatial hole burning.
In the present study we rely in different experimental measurements to show that the mode structure changes with the current are reflected onto the output power vs. current characteristics of the device. We address the evolution of the modal structure of a twin
ridge as we change the level of current injection among the two ridges. We show that the complex behavior during ridge coupling and the appearance of the lateral modes of the arrays are qualitatively represented in these curves. This information is important in two
related aspects: a) Determine when the two ridges start to interact, giving rise to a high frequency locking phenomena and b) Study appropriate models of the device that account for the observed phenomena.
The objective of this work is to analyse the dependence of the frequency response of Laterally Coupled Diode Lasers (LCDL) focusing on the separation between the laser ridges. A detailed study of the integrated optical spectra and frequency response is presented for LCDLs with 300 μm cavity length and separation between the ridges of 2, 4, 6, 8 and 10 μm. This study is of major importance as it defines the range of frequency locking for each ridge spacing and
also its dependence on the bias conditions applied.
A multimode model is necessary to describe the behavior observed in
a twin stripe diode laser. We will use a single-stripe version of the
device to calibrate the parameters enabling the model to be used in
the description and analysis of the twin-stripe 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.
This paper presents our initial work on high speed laterally coupled semiconductor diode lasers, where the structures to be studied will be two laterally coupled semiconductor diode lasers are expected to increase the modulation bandwidth by using the principles of coupling. We will show a study of the modeling used to find the static and spatial behavior of theses devices, obtaining the near and far field profiles and light power-current characteristic. Our primary goal will be to present the static and spatial behavior of the two InGaAsP laterally coupled semiconductor diode lasers using the effective-index method and Beam Propagation Method (BPM). Our results provide the static evolution of the current density profile, carrier density in the active layer and effective index shape at different injection current levels of a specific InGaAsP structure operating at 1.3 micrometer.
All manufactured sampled grating structures are mainly used for `wavelength tunability'. In this paper we succeeded in generating two modes by using Sampled Grating DFB laser. The two modes, will be optically heterodyned on a photodetector for mm-wave (via mode beating) signal generation. The advantage of that design is its size compactness (a single section, single electrode fed with a DC current supply), stable mode spacing, and relatively lower cost compared with other means of mm-wave generation. The simulation results will be presented using the well established model. Two parameters are shown to be affecting on the dual mode spacing and amplitude: the coupling coefficient and the carrier density variation along the (SG) structure. The former (coupling coefficient) mainly influences the mode spacing which is translated into the mm-wave frequency at the photodetector level. The anomalous coupling coefficient behavior leading to a quasi-stable mode spacing independent on the DFB section length increase is studied, interpreted and optimized. The latter (carrier density) plays a dramatic effect on that structure, resulting on fading away one of the two modes. We, succeeded in confining these two chirped modes into the structure by detuning the gratings. Finally, detuned grating effect will be explained.
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.
We present a study for an easy-going and fast modal analysis. We tackle the problem with three different approaches: the first one adopts a finalist viewpoint and is based on the 3D finite Difference Beam Propagation Method along imaginary axis. The second one is the numerical analysis' classical finite element method, applied to H. The third one consists in amounting to slab waveguides for which there are analytical solutions. We emphasize on the distinct natures of errors and, as an illustration, we study one optical ridge waveguide and one buried waveguide, made up with polymers. The methods are computed on 200-MHz PC and we discuss calculation time and accuracy. Eventually, through the conception of a candid coupler, we demonstrate what it costs to choose the wrong way, and in view of typical parameters of these structure, which is the most suitable method.
In this paper, we present first experimental results obtained on two and three tenninal edge-coupled InPfInGaAs heterojunction phototransistors showing that these devices seem very promising for microwave and millimeter wave applications.
Keywords : phototransistor , heterojunction, edge-coupled, microwave, millimeter wave, GaInAS/InP, photodetector
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]
In this paper, we present the optical behavior of waveguide PIN photodetectors for millimeter wave applications. The side illumination of these devices allows us to overcome the problem encountered with classical PIN top illuminated photodetectors, which is the compromise between high cut-off frequency and high responsivity. This is the reason why we have modeled PIN waveguide photodetectors grown on InP substrate. Our modeling is based on 3D and 2D FD Beam Propagation Method to describe the propagation of light in the photodetector and on the solution of classical semiconductor equations to describe the electrical behavior of the device. The model is applied to InP P+/GaInAs N-/InP N+ and InP P+/GaInAsP P+/GaInAs N-/GaInAsP N+/InP N+ structures. Cut-off frequencies up to 90 GHz can be obtained for very small devices, typically 12 micrometers for the device length and 5 micrometers for the rib width with 0.3 micrometers thickness of GaInAs absorbing layer, by neglecting parasitic effects due to boundary pads. This is also valid for structures with smaller ribs using a constant surface area. The external quantum efficiency of such a device is strongly dependent on the device structure (GaInAsP thickness, monomode or multimode structure), and also on the conditions of injection of light (width and position of the optical spot, angle of the optical beam with the device). A complete analysis of the quantum efficiency versus the influence of GaInAsP thickness, device length, GaInAs thickness, and optical injection has been performed. It was found that, using lens ended optical fiber, multimode waveguide structures are better devices compared to monomode ones, and can lead to quantum efficiency higher than 90%.
We analyze 45 degree(s) Self-Aligned Integrated Mirrors (SAIM) with Finite-Difference Beam Propagation Method. For the first time, we compare the intrinsic losses of three self-aligned structures that are used in integrated optics or optical interconnection circuits. We underline trade-off to make between diffraction and part of reflected power in the choice of self-aligned structures. We consider monomode polyimide optical waveguides and propagation in both quasi-TE and quasi-TM polarization modes. Comparisons are also made with semiconductor optical waveguides. It is shown that, in both cases, intrinsic losses of SAIM can be lower than 0.05 dB. This result is promising for the fabrication of future complex photonic circuits including several ten of mirrors.
We report on theoretical and experimental studies on the microwave passive reactive matching of high speed photodetectors. Such matching networks can substantially improve the power transfer of a microwave optical link. As an example, we relate two demonstrations which have been made, at a central frequency of 2 GHz, using both commercially available pigtailed PIN photodiode and laboratory made MSM detector. In both cases, matching networks are fabricated using transmission lines and comparison with unmatched devices is made in order to determine the improvement of the power transfer. Trade-offs between working frequency, bandwidth and available improvement in power transfer are presented taking into account parasitics value and the intrinsic capacitance of the detector. The extent of such a matching scheme to monolithic integration in order to increase either working frequency or power improvement is also reported as conclusion.
We present in this paper the results of two different modelings of photodetectors. The first is based on FD-BPM and presents the study of a waveguide PIN photodetector structure grown on InP substrate. It gives the possible cut-off frequency for such a photodetector. The second one is a modeling of a conventional PIN photodiode including the effects of the external circuit. The goal of this modeling is to analyze the behavior of the photodetector under very high optical power. We considered the case of an optical signal sinusoidally modulated at 20GHz and analyzed the output photocurrent in order to give the limitations of the photodetector.
The first demonstration of fabrication of a monolithic photoreceiver using selective growth and lattice mismatch heteroepitaxies is presented. The photoreceiver includes a GaInAs/GaAs M.S.M. photodetector, a GaAs MESFET and a serial inductor which achieves a resonant effect. A dielectric mask was used to selectively grow the GaInAs/GaAs heteroepitaxies on the GaAs epilayers which, themselves, have been grown on a silicon substrate. In comparison with a PIN photodiode loaded with a 50 Omega resistor, approximately 10 dB gain has been obtained at 7 GHz.
Progress in the area of integrated receivers is surveyed, with emphasis on the use of large lattice mismatch epitaxy, selective growth, and planar structure to reduce the technological difficulties associated with the fabrication of these integrated circuits. Some examples of monolithic integration of photodetectors with transistors and optical waveguides are presented. Particular attention is given to a monolithic resonant photoreceiver for long-wavelength and microwave applications, fabricated using lattice mismatch heteroepitaxies and selective growth.
Planar photoconductors made with GaAs on silicon substrate have been studied with respect to static and dynamic responsivities as well as noise levels in the 1 Hz - 100 kHz frequency range. The results obtained have led to the determination of the specific detectivity which in turn is compared to those of GaAs planar photoconductors and Si photodiodes.
We present the electrical behavior of an integrated
waveguide/photodetector based on the absorption of the evanescent optical
field in an absorbing layer, deposited on the top of the waveguiding layer. We
establish the expression of the electron-hole pair generation rate, for such a
device. Then, we apply this result to the calculation of the dynamic quantum
efficiency of an integrated waveguide/PIN-photodiode. The static and dynamic
behaviors of GaInAs PIN-photodiodes monolithically integrated on a classical
n/nt InP homostructure waveguide or on a GaInAsP/InP heterostructure
waveguide are discussed and optimized structures are pointed out.
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