In the strong light-matter interaction regime, quantum vacuum field effects on coupled hybrid states are highly enhanced. One building block of such hybrid quantum system is a plasmonic nanocavity coupled with quantum emitters in the strong coupling (SC) limit and further. Here, we design and fabricate a low-mode volume plasmonic cavity and observe plasmon resonances in the visible range, based on the nanoparticle over mirror (NPoM) array structure. We show spectral tunability of this resonance with the nanostructure dimensions, and good agreement between optical characterization and numerical simulations by FDTD.
Numerous medical conditions require extensive monitoring of diverse biomarkers, imposing a significant time and effort burden on healthcare professionals. This underscores the need for fast, reliable, and personalized point-of-care diagnostic tools. In the context of organ transplantation, the physiological status of a brain deceased organ donor requires comprehensive surveillance, accompanied by appropriate medical interventions to mitigate organ degradation. An effective strategy for monitoring this degradation involves tracking the progression and, ideally, the onset of the inflammatory response, the so-called ”cytokine storm”, by monitoring specific biomarkers: micro-RNAs. We propose two approaches based on a surface plasmon resonance imaging biosensor that combine various methodologies to amplify the hybridization signal of an oligonucleotide duplex (sandwich assay or bimaterial nanostructured biochip). In a proof-of-concept experiment involving a protein oligonucleotide complex in a sandwich assay, we successfully demonstrate signal amplification by one order of magnitude. Additionally, using the contribution of localized surface plasmons induced by nanostructuring the biochip, our simulations predict a further significant gain in amplification.
Fluoranthene and Pyrene (PAHs) airborne particles are well known for their mutagenic and carcinogenic properties. Manipulation of such nanoparticles below 100 nm makes it challenging due to their low polarizability and dielectric properties. Current optical nano-tweezer designs such as trench, slot and Hybrid Plasmonic Waveguides (HPWG) provides a strong gradient force for trapping, but they often have ≤ 50 nm gaps and have very low fabrication tolerances. In this work, we show the modeling of optical forces and sensitivity of different waveguide structures to sense large numbers of particles to monitor the Air Quality Index (AQI). To increase the trapping gaps and sensitivity in HPWG, we have designed them to use radiation modes of the dielectric waveguides. We call this phenomenon a “mode-lift”. Here we present the numerical and experimental results of industrially compatible integrated photonic sensors such as strip, slot, subwavelength grating (SWG) and HPWG used for measuring AQI.
This work aims to develop polymer-based optical micro-resonator sensors, operating in the visible range and sensitive for homogeneous in-situ detection of pollutants in aqueous medium. This paper demonstrates that using a porous silica cladding (ns = 1.2) enhances significantly the interaction of the evanescent field with the analytes by modifying the propagation properties of the guided optical mode. The results improve sensitivity without complicating the design and avoiding surface chemical functionalization classically used for such application. Detection experiments based on real part refractive index change in the visible range have been conducted using different glucose concentrations. A sensitivity at the state-of-the-art of 255 ± 12 nm/RIU has been achieved at 760 nm for micro-resonator polymer waveguides on porous silica. These promising results enable the use of our devices in sensors to detect both real and imaginary parts of the analyzed medium refractive index, as well as analysis of complex environments.
We present a Surface Plasmon Resonance Imaging (SPRI) biochip system to quantitatively detect micro-RNAs involved in the cytokine storm during an inflammatory response. The thiol composition of the self-assembled monolayer on the biochip gold surface was tuned to maximize the capture of RNAs at low concentrations. To further amplify this signal, we have developed a sandwich-like assay using oligonucleotides functionalized gold nanoparticles (AuNPs), synthesized at ambient temperature and optimized to have a high solubility in saline solutions. Sub-picomolar detection limit of those small RNAs was achieved with all these combined improvements.
This study presents the development and optimization of AlN-based optical waveguides and photonic devices for 1.55 μm applications, utilizing a CMOS-compatible sputtered thin film technology. The fabrication employs a two-step photoresist technique to fabricate AlN core waveguides with low propagation losses and other optical devices, such as a 1×2 multimode interference (MMI) coupler, Mach-Zehnder interferometers and ring resonators. The results of this study highlight the potential for efficient and cost-effective fabrication of AlN-based integrated optical circuits and pave the way for further research and development in the field of integrated optics.
Point-of-care tests (POCT) are important for detecting illnesses and monitoring patients without the need of a medical laboratory. To be useful, POCT must be sensitive, specific, integrated, and affordable. Since the early 2000s, integrated photonics have offered a possible solution for this problem. In particular, silicon micro-ring resonators represent a compact and sensitive choice known in the industry. This paper details the design, fabrication, and characterization of two methods for improving the performance of ring resonators by engineering their cross section. More precisely, improving devices made out of silicon nitride in an industrial environment to work in the infrared (around 1.31 µm).
The first approach is to selectively excite the first order mode of the ring resonator’s waveguide. The first order mode, with its greater exposure to the sensing liquid than the fundamental mode, results in a higher device sensitivity. The second method consists in coupling a dielectric mode with a surface plasmon polariton (SPP) forming a hybrid plasmonic waveguide. Hybrid plasmonic waveguides combine the low losses of the dielectric mode with the high sensitivity of the SPP, which increases the sensitivity in comparison to conventional dielectric ring resonators. Furthermore, hybrid plasmonic micro-ring resonators make possible a stable and easy differential functionalization.
Through the optical characterization of the devices, this study shows an experimental sensitivity of first order ring resonators of over 200 nm/RIU* and of hybrid plasmonic devices of 300 nm/RIU*. This demonstrates improvement with respect to the reference silicon nitride dielectric ring (120 nm/RIU*). Characterizations were performed using a PolyDiMethylSiloxane (PDMS) fluidic system to prove the compatibility of the substrate to POCT applications.
This paper shows two alternative approaches to integrated nano-photonic sensing for point of care testing. The proposed structures, demonstrate not only a higher sensitivity, but consider selectivity and manufacturing issues, which are fundamental for POCT development.
*RIU = Refractive Index Unit
Optical ring micro-resonators (OMR) can be integrated onto chips to obtain sensitive, robust, low cost and portable sensor systems. They are used for in-situ real time detection of specific molecules by specialized or non- specialized persons. Target analytes, homogeneously spread in the cladding layer, induces a complex refractive index variation Δncl of the OMR waveguides upper cladding.
In this study, we propose an optimized analytical approach to OMR designs in terms of bulk sensitivity.
Those type of sensors are based on the evanescent field sensing. Interaction between the evanescent field and the analytes induces resonance wavelengths modifications. The main sensing strategy is based on resonant wavelength shift measurement. However, contrast variation, due to the absorption coefficient linked to analytes concentration, can also be measured. Colorimetric reactions, used to obtain a specific sensor, change significantly the light intensity in a specific peak of the transmission spectrum. This is due to the complex formation between a specific ligand and a heavy metal, such as hexavalent chromium and 1,5 diphenylcarbazide.
From the well-known ring resonator’s transmission expression, we can establish an analytical model of sensitivity’s dependence on geometric dimensions. Sensitivity in influenced by the round-trip attenuation coefficient a, the auto-coupling coefficient τ, the optical path and the ratio of guided power into the cladding Γcl. We validated our approach with FDTD simulation of OMR’s response for a 15 μm radius. This analytical approach makes it possible, from the waveguide propagation structure and propagation losses, to obtain both the optimal ring radius and the resonator gap in order to obtain maximum sensitivity.
Based on optical characterization of OMR, measured variations of 1% power drop at resonance should allow variation measurement on the extinction coefficient of ∆ni = 10−6.
Surface plasmon resonance imaging (SPRI) biosensors allow sensitive, real-time and label-free detection of biological species in fluids when they bound to the sensing surface. However, their sensitivity is now close to the theoretical limit. In particular, at ultra-low target concentration, the main limit is the diffusion of the biological target (protein, DNA, bacteria…) to the gold film surface. To locally increase the target concentration on the sensitive surface and overcome such diffusion limit, active mass transport of analytes can be induced by non-uniform electric fields using dielectrophoresis (DEP) and alternative-current electroosmosis (ACEO) flow. Depending on the frequency of the electric field applied and the conductivity of the suspension medium, DEP and ACEO can concentrate biological objects on electrodes. This work focuses on the trapping and the detection of bacteria. The gold film used for SPR imaging is also used as electrode for particle collection, after photolithography and wet etching. To obtain the most efficient electrode design, numerical simulations were performed to estimate the trapping force applied on bacteria in the fluidic chamber volume depending on the geometry of the electrodes. SPR biochips obtained were mounted in the Kretschmann configuration. Then, a DI water solution containing E.coli bacteria was injected in the fluidic chamber of the chip. AC voltage (10Vpp, 1 kHz) was applied. The arrival of bacteria on the sensing zone is monitored by a strong jump of the SPR signal when no signal was observed without mass transport. The easy integration of such DEP/ACEO-assisted SPR chips on commercial SPR benches makes them suitable fur ultralow detection of a wide range of biological species, from biomolecules to pathogens.
Few studies in literature have try to quantitatively compare the 2T model with experimental data at very short time scale and study the dependency and importance of model’s parameters. We have developed a new numerical model and fitting algorithm which combined the 2T model, thermal conduction and 3D FEM EM code to link the spatial distribution of temperature to the optical reflectivity of the sample. Using a state-of-the-art pump-probe setup allowing the acquisition of the full spectro-temporal optical response of the sample, we have compared measurements on thin gold films and array of nanostructures with our model.
We have demonstrated, numerically and experimentally, that optimized nanostructured plasmonics substrates can generate new hybrid plasmonic modes that possess the spectral dispersion of propagating plasmon but with a much lower propagating length. The imaging performances of these nanostructured SPR chips were recently assessed by studying cellular responses following biochemical stimulation, in particular by real-time monitoring of integrity changes in confluent endothelial cell layer. Improvement in spatial resolution has resulted in an increase in detection sensitivity to cellular activity, with no detectable disturbances in cellular behavior due to the presence of nanostructures.
Surface Plasmon Resonance (SPR) biosensors are standard tools for chemical and biological sensing. They provide sensitive, real-time and label-free detection of biological species in fluids. However, their performance (time and detection threshold) is now close to the theoretical limit. In particular, at low target concentrations, sensitivity is limited by the diffusion of the target analyte to the sensor surface. To overcome the diffusion limit, non-uniform electric fields can be used to induce electrokinetic effects (dielectrophoresis and alternative-current electroosmosis) which attract analytes toward the surface sensing zone. This work proposes to pattern the gold film used for SPR detection and use it as electrodes for the electric field generation. The magnitude of the electrokinetic effects and resulting analyte trapping efficiency of different electrodes designs were studied numerically with COMSOL by modeling the dielectrophoretic and drag forces induced by the AC-electroosmotic flow. A biochip, which consists of a structured gold film on a glass substrate, was mounted in the SPR Kretschmann configuration in contact with a fluidic cell to enable the injection of analyte and rinsing solutions. SPR imaging allowed us to compare the spatial distribution of the SPR response both a planar metal zone similar to a conventional SPR sensor as well as on the electrodes. After microbeads injection into the fluidic cell and application an AC voltage (V=1Vpp, f=1kHz), a strong SPR signal jump was observed due to the analyte’s arrival on the sensing zone. As a result of the electrokinetic effects, the detection threshold of mass transport assisted SPR chips was improved by several orders of magnitude.
Bacterial pathogen contamination is the leading cause of both foodborne and hospital-acquired diseases. Therefore, there is a constant need for more effective, reliable and easy-to-use microbiology study techniques and detection systems. This is critical, as pathogenic contamination has become a central issue in the food industry and healthcare. This paper describes the novel use of resolution-optimized prism-based surface plasmon resonance imaging (resolution around the size of a bacteria) and data processing to further understand the behavior of individual bacteria near specifically engineered surfaces. We show that our technique is effective for both the dynamic study of individual bacteria behavior near interface on a statistically representative sample, and their interactions with chemically functionalized surfaces.
KEYWORDS: Sensors, Signal detection, Amplifiers, CMOS sensors, Biological research, Photodiodes, Diffusion, Semiconductors, Signal to noise ratio, Temperature metrology
The CMOS buried multi-junction (BMJ) detector with multiple outputs has distinct spectral responses that may be exploited for applications such as bio-chemical analysis. We tackle here dark current issue by identifying different components inside the detector structure. The identification methods are based on the observation of bias and temperature dependence, as well as measurements of test detector chip integrating different design variations. Surface thermal generation may become predominant when the detector size shrinks, thus causing dark current degradation. To prevent this effect, we propose a low-sized detector structure with passivation of all its surrounding Si/SiO2 interface areas.
Also for the detector readout, we present a multi-channel charge-amplifier architecture with noise analysis. Effects of noise coming from amplifiers and related to the coupled detector’s dynamic conductances are illuminated. To pick up weak signals, synchronous detection can be implemented. A BDJ (Buried Double Junction) detector chip designed with a switched-phase architectural approach gives a minimum detectable signal of 15μlx@555nm or 1μlx@555nm at 27°C or – 10°C, for an integration time of 3s or 45s respectively.
Glass substrates have been used for decades to create biosensors due to their biocompatibility, low thermal conductivity, and limited fluorescence. Among the different types of sensors, those based on surface plasmon resonance (SPR) allow exploitation of the sensing lightwave at the vicinity of the sensor surface where small entities such as DNA or proteins are located. In this paper, ion-exchanged waveguides and SPR are combined to create a multianalyte optical sensor integrated onto glass. First the principle of operation is introduced, then the theoretical analysis and design of the sensing element. Simulations have been carried out using the Aperiodic Fourier Modal Method (AFMM) and a custom software that handles ion-exchange index-profiles. Fabrication and characterization processes are also presented. Finally the first experimental spectra are displayed and discussed. The sensor presents a bulk sensibility of 5000nm/RIU.
A design incorporating surface plasmon resonance (SPR) biosensing and surface acoustic wave (SAW) active
microfluidic mixing, integrated on a single LiNbO3 piezoelectric substrate, is presented. Validation experiments show
that SAW-mixing (microstreaming) results in accelerated binding kinetics (time-to-saturation) for a standard assay with
appropriate SAW excitation parameters. Since both SPR sensors and SAW transducers can be fabricated simultaneously
using low-cost microfabrication methods, the proposed design should contribute to improved lab-on-chip devices for
detecting and identifying biomolecules of interest with greater accuracy and speed across multiple applications.
The direct simultaneous acquisition of coherent imaging and strain information is of particular importance in the biomechanical characterization of biological tissue. This type of simultaneous information acquisition can be accomplished using a coupled photorefractive holography and shearography system for imaging and strain measurements, respectively. Optical scattering in a conventional speckle shearing interferometer rapidly reduces the contrast of the shearing fringes, thereby limiting the use of such interferometers with opaque surfaces. By coupling photorefractive holography with speckle shearing interferometry, properties of the photorefractive effect (spatial high-pass filtering and temporal low-pass filtering) combine to restore the shearing fringe contrast and enable strain imaging in diffusing media. This effect is demonstrated using synthetic scattering phantoms built from suspensions of silica spheres in water.
Surface plasmon resonance (SPR) sensing is now widely used in biosensing applications. There is significant scope to
reduce the cost and complexity of existing commercial devices by increasing the level of optical integration, and also of
enhancing the sensitivity through the use of periodic nanostructures to increase the electromagnetic field response. We
will present a SPR sensor design that addresses these two issues. This design utilizes a diffractive optical element (DOE)
which is integrated directly into the sensor-head and which significantly reduces the optical complexity. It is intended for
eventual mass replication via a suitable molding technique. This system is designed to be used within an angular sensing
scheme and the DOE delivers the required 15° angular beam divergence. A carefully developed signal processing
scheme is then used to extract the maximum possible information from the detected signal. The sensor surface
incorporates gold nanogratings and guided molecular self-assembly for the immobilization of ligand-specific probes to
achieve a higher sensitivity than can be achieved with a flat surface. The nanostructured surface is also designed for
eventual reproduction via molding or imprint approaches. The sensor-head modeling was performed using rigorous
coupled-wave analysis (RCWA) and the boundary element method (BEM) whereas the beam-steering optics were
modeled using ray tracing. The modeling and experimental results will be presented.
An apparatus for measuring the mechanical properties of thin living biological membranes such as pericardium (the sac which encloses the heart) is presented. The apparatus, using 16 actuators to apply stresses in the plane of the membrane, measures in-plane displacements and strain by means of electronic speckle pattern interferometry (ESPI). As opposed to conventional speckle interferometers which use light reflected from the surface under test, the apparatus presented here collects the light transmitted through the membrane, as pericardium is translucent and reflects very little light. Furthermore, in order to be preserved in a healthy state, the biological membrane must be kept immersed in a bath of physiological solution during the measurement experiments. Results of mechanical stretch experiments are presented where the infinitesimal strain tensor components were measured over the entire surface of a 10 mm diameter circular specimen of pericardium.
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