Showing papers on "Total internal reflection published in 2017"

Demonstration of a self-pulsing photonic crystal Fano laser

Abstract: Fano interference and nonlinearity are exploited to achieve self-pulsing of a laser at gigahertz frequencies. The semiconductor lasers in use today rely on various types of cavity, making use of Fresnel reflection at a cleaved facet1, total internal reflection between two different media2, Bragg reflection from a periodic stack of layers3,4,5,6,7,8, mode coupling in a high contrast grating9,10 or random scattering in a disordered medium11. Here, we demonstrate an ultrasmall laser with a mirror, which is based on Fano interference between a continuum of waveguide modes and the discrete resonance of a nanocavity. The rich physics of Fano resonances12 has recently been explored in a number of different photonic and plasmonic systems13,14. The Fano resonance leads to unique laser characteristics. In particular, because the Fano mirror is very narrowband compared to conventional laser mirrors, the laser is single mode and can be modulated via the mirror. We show, experimentally and theoretically, that nonlinearities in the mirror may even promote the generation of a self-sustained train of pulses at gigahertz frequencies, an effect that has previously been observed only in macroscopic lasers15,16,17,18. Such a source is of interest for a number of applications within integrated photonics.

Refractive index measurements of photo-resists for three-dimensional direct laser writing

Abstract: Femtosecond 3D printing is an important technology for manufacturing of nano- and microscopic devices and elements. Crucial for the design of such structures is the detailed knowledge of the refractive index in the visible and near-infrared spectral range and its dispersion. Here, we characterize 5 photoresists that are used with femtosecond 3D direct laser writers, namely IP-S, IP-Dip, IP-L, IP-G, and OrmoComp with a modified and automized Pulfrich refractometer setup, utilizing critical angles of total internal reflection. We achieve an accuracy of 5⋅10−4 and reference our values to a BK-7 glass plate. We also give Abbe numbers and Schott Catalog numbers of the different resists. Their refractive indices are in the 1.49-1.57 range, while their Abbe numbers are in the range between 35 and 51.

Tunable resonant Goos–Hänchen and Imbert–Fedorov shifts in total reflection of terahertz beams from graphene plasmonic metasurfaces

Abstract: Highly tunable enhanced lateral displacements in the center of gravity of a totally reflected light beam from a graphene plasmonic metasurface are investigated. Multiple reflections of the incident beam, and the resonance coupling between the incident beam and the surface modes of the graphene metasurface in each reflection, are employed to enhance the Goos–Hanchen and Imbert–Fedorov shifts in the proposed structure. It is shown that spatial Goos–Hanchen and Imbert–Fedorov shifts as high as 1089λ0 and −44.66λ0 (λ0: incident wavelength) are achievable in the proposed structure. The effects of different parameters, including the incident beam waist, temperature, the scattering time, and the chemical potential of the graphene, on the shift values are then studied. Because of the strong light confinement in the surface modes of the graphene metasurface, the dispersion properties of these modes, and, therefore, the coupling strength between the incident beam and these modes, are highly sensitive to the parameters of the reflecting structure and the incident beam itself. The high sensitivity of the coupling strength between the incident beam and the surface modes is then exploited to tune the shift values. It is shown that by introducing a small change of ΔμC=0.02 eV in the chemical potential of the graphene, the spatial Goos–Hanchen and Imbert–Fedorov shift variations of 855λ0 and −31λ0 can be achieved, respectively. The wide range of lateral shift variations along with the relatively small required actuation power support the application of the proposed structure in the realization of optical devices, such as temperature sensors and switches.

Controlling evanescent waves using silicon photonic all-dielectric metamaterials for dense integration

Abstract: Ultra-compact, densely integrated optical components manufactured on a CMOS-foundry platform are highly desirable for optical information processing and electronic-photonic co-integration. However, the large spatial extent of evanescent waves arising from nanoscale confinement, ubiquitous in silicon photonic devices, causes significant cross-talk and scattering loss. Here, we demonstrate that anisotropic all-dielectric metamaterials open a new degree of freedom in total internal reflection to shorten the decay length of evanescent waves. We experimentally show the reduction of cross-talk by greater than 30 times and the bending loss by greater than 3 times in densely integrated, ultra-compact photonic circuit blocks. Our prototype all-dielectric metamaterial-waveguide achieves a low propagation loss of approximately 3.7 dB/cm, comparable to those of silicon strip waveguides. Our approach marks a departure from interference-based confinement as in photonic crystals or slot waveguides, which utilize nanoscale field enhancement. Its ability to suppress evanescent waves without substantially increasing the propagation loss shall pave the way for all-dielectric metamaterial-based dense integration.

Influence of evanescent wave on birefringent microplates.

Abstract: Mechanical action caused by the optical forces connected with the canonical momentum density associated with the local wavevector or Belinfante’s spin angular momentum is experimentally verified. The helicity-dependent and the helicity-independent forces determined by spin momenta of different nature open attractive prospects for the use of optical structures for manipulating minute quantities of matter of importance in nanophysics, nanooptics and nanotechnologies, precision chemistry and pharmacology and in numerous other areas. Investigations in this area reveal new, extraordinary manifestations of optical forces, including the helicity-independent force caused by the transverse helicity-independent spin or vertical spin of a diagonally polarized wave, which was not observed and exploited up to recently. The main finding of our study consists in a direct experimental demonstration of the physical existence and mechanical action of this recently discovered extraordinary transverse component of the spin here arising in an evanescent light wave due to the total internal reflection of a linearly polarized probing beam with azimuthal angle 45° at the interface between the birefringent plate and air, which is oriented perpendicularly to the wavevector of an evanescent wave and localized over the boundary of the transparent media with polarization-dependent refraction indices.

Large-Scale Silicon Nanophotonic Metasurfaces with Polarization Independent Near-Perfect Absorption

Abstract: Optically thin perfect light absorbers could find many uses in science and technology. However, most physical realizations of perfect absorption for the optical range rely on plasmonic excitations in nanostructured metallic metasurfaces, for which the absorbed light energy is quickly lost as heat due to rapid plasmon decay. Here we show that a silicon metasurface excited in a total internal reflection configuration can absorb at least 97% of incident near-infrared light due to interferences between coherent electric and magnetic dipole scattering from the silicon nanopillars that build up the metasurface and the reflected wave from the supporting glass substrate. This “near-perfect” absorption phenomenon loads more than 50 times more light energy into the semiconductor than what would be the case for a uniform silicon sheet of equal surface density, irrespective of incident polarization. We envisage that the concept could be used for the development of novel light harvesting and optical sensor devices.

Experimental investigation of the propagation properties of bloch surface waves on dielectric multilayer platform

Abstract: The periodic dielectric multilayers sustaining Bloch surface waves have been proposed as a platform for the sensing applications and the two dimensional integrated optics. In this paper, we present the experimental and theoretical investigation of propagation properties of Bloch surface waves, for example propagation length and refractive index of the surface mode, at the interface of a dielectric multilayer platform. We use thin layers (~λ/25) of titanium dioxide as an additional layer of high index material. We exploit multi-heterodyne scanning near-field optical microscopy and total internal reflection configuration as a near-field and far-field characterization tools. The longest propagation length is achieved when the multilayer is designed to have the dispersion curve positioned close to the middle of the photonics band gap. We measure a Bloch surface wave mode of propagation length 3.24 mm and of an effective refractive index contrast 0.15. The experimental results are in conformity with theoretical results. This study paves a way to realize efficient and compact two dimensional components and systems.

Reflection compensation mediated by electric and magnetic resonances of all-dielectric metasurfaces [Invited]

Abstract: All-dielectric nanostructures have recently emerged as a promising alternative to plasmonic devices, as they also possess pronounced electric and magnetic resonances and allow effective light manipulation. In this work, we study optical properties of a composite structure that consists of a silicon nanoparticle array (metasurface) and high-index substrate aiming at clarifying the role of substrate on reflective properties of the nanoparticles. We develop a simple semi-analytical model that describes interference of separate contributions from the nanoparticle array and the bare substrate to the total reflection. Applying this model, we show that matching the magnitudes and setting the π-phase difference of the electric and magnetic dipole moments induced in nanoparticles, one can obtain a suppression of reflection from the substrate coated with metasurface. We perform numerical simulations of sphere and disk nanoparticle arrays for different permittivities of the substrate. We find full agreement with the semi-analytical results, which means that the uncoupled-element model adequately describes nanostructure reflective properties, despite the effects of induced bi-anisotropy. The model explains the features of the reflectance spectrum, such as a number of dips and their spectral positions, and shows why it may not coincide with the spectral positions of Mie resonances of the single nanoparticles forming the system. We also address practical aspects of the antireflective device engineering: we show that the uncoupled-element model is applicable to the structures on top of silicon substrates, including lithographically defined nanopillars. The reflectance suppression from the nanoparticle array on top of the silicon substrate can be achieved in a broad spectral range with a disordered nanoparticle array and for a wide range of incidence angles.

Enhanced spin Hall effect of reflected light with guided-wave surface plasmon resonance

Abstract: The photonic spin Hall effect (SHE) has been intensively studied and widely applied, especially in spin photonics. However, the SHE is weak and is difficult to detect directly. In this paper, we propose a method to enhance SHE with the guided-wave surface-plasmon resonance (SPR). By covering a dielectric with high refractive index on the surface of silver film, the photonic SHE can be greatly enhanced, and a giant transverse shift of horizontal polarization state is observed due to the evanescent field enhancement near the interface at the top dielectric layer and air. The maximum transverse shift of the horizontal polarization state with 11.5 μm is obtained when the thickness of Si film is optimum. There is at least an order of magnitude enhancement in contrast with the transverse shift in the conventional SPR configuration. Our research is important for providing an effective way to improve the photonic SHE and may offer the opportunity to characterize the parameters of the dielectric layer with the help of weak measurements and development of sensors based on the photonic SHE.

Acceleration of sub-relativistic electrons with an evanescent optical wave at a planar interface.

Abstract: We report on a theoretical and experimental study of the energy transfer between an optical evanescent wave, propagating in vacuum along the planar boundary of a dielectric material, and a beam of sub-relativistic electrons. The evanescent wave is excited via total internal reflection in the dielectric by an infrared (λ = 2 μm) femtosecond laser pulse. By matching the electron propagation velocity to the phase velocity of the evanescent wave, energy modulation of the electron beam is achieved. A maximum energy gain of 800 eV is observed, corresponding to the absorption of more than 1000 photons by one electron. The maximum observed acceleration gradient is 19 ± 2 MeV/m. The striking advantage of this scheme is that a structuring of the acceleration element’s surface is not required, enabling the use of materials with high laser damage thresholds that are difficult to nano-structure, such as SiC, Al2O3 or CaF2.

Graphene Based Terahertz Light Modulator in Total Internal Reflection Geometry

Abstract: Modulation of visible light has been easily achieved for decades, but modulation of terahertz (THz) light still remains a challenge. To address this issue, the Fresnel equations have been developed to describe a conductive interface in a total internal reflection geometry and reveal a new approach for modulation. To demonstrate this new mechanism, a broadband device achieving a modulation depth greater than 90% between 0.15 and 0.4 THz, and reaching a maximum of 99.3% at 0.24 THz has been designed. The modulation is achieved by applying a gate voltage between −0.1 and 2 V to a graphene layer in a total internal reflection geometry. Compared to conventional designs, the high modulation is realized without assistance from metamaterial structures, resonant cavities, or multistacked graphene layers. Thus, the design is efficient and easy-to-fabricate and can be easily retrofitted to most existing THz systems. This work opens up a new avenue of research as the device has verified the theory and demonstrates how it can be used to make practical devices, bringing a promising new paradigm for THz modulation, thin-film sensing, and noninvasive material characterization.

Surface Plasmons\/Polaritons, Surface Waves, and Zenneck Waves: Clarification of the terms and a description of the concepts and their evolution.

Abstract: The first objective of this article is to explain what surface plasmons and surface plasmon polaritons are. The term surface plasmons (SPs) was first coined in the middle of the 20th century to study the response of thin metal foils at petahertz frequencies when subjected to fast electron bombardment. SPs are coherent electron oscillations that exist at the interface between two materials where the real part of the permittivity changes sign across the interface. When an SP couples with a photon, the resulting hybrid excitation is called a surface plasmon polariton (SPP). SP refers to the charge oscillations alone, while SPP refers to the entire excitation of the charge oscillations and the electromagnetic (EM) wave. Under the right conditions, the photon can excite a longitudinal wave of electrons in the metal. The second objective is to describe the evolution of these concepts over the years and illustrate their relation to a surface wave and not to a Zenneck wave. Both Zenneck and surface waves are transverse magnetic (TM) waves. The surface waves thus cannot be excited by transverse EM (TEM) waves but rather by an electron beam that can be effectively generated by a source of electrons or a quasiparticle such as an evanescent wave, which can tunnel through the medium and thus excite the electrons. This electron wave produces its own EM wave, and this plasmonic wave is confined to a very small region near the interface. Hence, SPP is a surface wave with a longitudinal field component that propagates at the interface between a metal and a dielectric at petahertz when the conditions are right and can propagate along the metal-dielectric interface at a wavelength that is shorter than that of incident light until its energy is lost either via absorption in the conductivity of the metal or through radiation in free space. The longitudinal surface wave of an SPP is sometimes wrongly associated with a Zenneck wave. A Zenneck wave is produced at the zero of the reflection coefficient of a plane incident TM wave (at the Brewster angle of incidence) on an air-dielectric interface, whereas surface waves are produced when the TM reflection coefficient is infinite. Both the Zenneck wave and the surface wave are TM waves and are nonradiating, as they have, in general, exponentially decaying fields with distance. For the Zenneck wave, the evanescent transverse field components do not change appreciably with frequency (because the phenomenon of Brewster angle is independent of frequency), whereas for a surface wave, with an increase of the frequency the wave is more closely coupled to the surface. This property makes it possible to distinguish between these two evanescent waves. SPP is generally coupled with Raman scattering and not with Rayleigh scattering. These points are illustrated in the remainder of the article. Hence, surface plasmons/polaritrons are surface waves that are the solution of Maxwell's equations unless perhaps there is a resonant Raman scattering, which is equivalent to exciting the structure with an incident frequency corresponding to the electronic absorption bands, as illustrated in "A Survey of the Various Natures of Light Scattering."

Ultrasonic detection based on polarization-dependent optical reflection

Abstract: Owing to their extremely wide bandwidths, pure optical ultrasonic detection methods are gaining increasing interest. In this Letter, we proposed a simple ultrasonic detector that is based on the polarization-dependent optical reflection. When the acoustic wave reaches the liquid-glass interface, the acoustic pressure changed the relative refractive index between two media, leading to perturbations in the reflectance of the optical probe beam in glass. Unlike previous studies that detected the modulations in the intensity of the reflected beam, our method, named “polarization-dependent reflection ultrasonic detection (PRUD),” detects the intensity difference between two polarization components of the same probe beam. The PRUD significantly increased the sensitivity. Besides a phantom study, we also successfully detect weak photoacoustic waves in an in vivo animal experiment. This novel method can provide a simple way for ultrasonic detection, which will have great potential for ultrasound and photoacoustic imaging and sensing.

Dual channel multilayer-coated surface plasmon resonance sensor for dual refractive index range measurements.

Abstract: We present a novel multilayer-coated surface plasmon resonance sensor for dual refractive index range measurements based on a capillary structure. The sensing elements include an internally coated Ag layer and an externally coated bilayer of Au with an overlayer of thin indium tin oxide (ITO). The internal Ag layer was sensitive to higher refractive index (RI) medium while the external Au/ITO layer was sensitive to lower refractive index medium. We evaluated the sensor performance by measuring RI changes in two channels, RI sensitivities were -1951 nm/RIU and 2496 nm/RIU, respectively. This compact, low-cost large RI detection range SPR sensor offers the possibility for wider RI detection range and highly sensitive SPR studies in industry and chemical sensing.

Focusing hard x rays beyond the critical angle of total reflection by adiabatically focusing lenses

Abstract: In response to the conjecture that the numerical aperture of x-ray optics is fundamentally limited by the critical angle of total reflection [Bergemann et al., Phys. Rev. Lett. 91, 204801 (2003)], the concept of adiabatically focusing refractive lenses was proposed to overcome this limit [Schroer and Lengeler, Phys. Rev. Lett. 94, 054802 (2005)]. We present an experimental realization of these optics made of silicon and demonstrate that they indeed focus 20 keV x rays to a 18.4 nm focus with a numerical aperture of 1.73(9) × 10−3 that clearly exceeds the critical angle of total reflection of 1.55 mrad.

Giant Terahertz-Wave Absorption by Monolayer Graphene in a Total Internal Reflection Geometry

Abstract: We experimentally demonstrated significant enhancement of terahertz-wave absorption in monolayer graphene by simply sandwiching monolayer graphene between two dielectric media in a total internal reflection geometry. In going through this structure, the evanescent wave of the incident terahertz beam interacts with the sandwiched graphene layer multiple (up to four) times at varying incidence angles. We observed extremely large attenuation (up to ∼70% per reflection), especially for s-polarized radiation. The experimental results are quantitatively consistent with our calculations, where we modeled the experiment as an electromagnetic wave reflection process in monolayer graphene. We also derived analytical expressions for the absorptance, showing that the absorptance is proportional to the amount of Joule heating on the graphene surface induced by the terahertz radiation.

Bound states in the continuum in fiber Bragg gratings

Abstract: Optical fibers typically confine light through total internal reflection or through photonic bandgaps. Here we show that light can be perfectly guided in optical fibers through a different mechanism based on bound states in the continuum (BICs). In fibers with periodic Bragg gratings, we predict bona fide BICs in pure-polarization modes, as well as quasi-BICs in hybrid-polarization modes. These guided modes exist robustly without the need for fine structural tuning, and they persist even with the very small grating index contrasts that are available in conventional fiber Bragg gratings. The suppression of radiation loss arises from the coupling between a weakly-radiating mode and a strongly-radiating one. This finding opens the possibility of guiding light with BICs in optical fibers and their applications in distributed fiber sensors, in-line fiber filters, and high-power fiber lasers.

Analysis of high-Q photonic crystal L3 nanocavities designed by visualization of the leaky components.

Abstract: We experimentally study photonic crystal L3 nanocavities whose design Q factors (Qdesign) have been improved with the visualization of leaky components design method. The experimental Q values (Qexp) are monotonically increased from 6,000 to 2,100,000 by iteratively modifying the positions of some of the air holes, as determined by the referred design method. We investigate the Qexp tolerance to imperfections in the fabricated samples, which reveals that the cavities improved by the visualization method tend to lose some tolerance to structural differences between the fabricated samples and the design values.

Electromagnetic field enhancement in Bloch surface waves

Abstract: We present a systematic comparison between guided modes supported by slab waveguides and Bloch Surface Waves (BSWs) propagating at the surface of truncated periodic multilayers. We show that, contrary to common belief, the best surface field enhancement achievable for guided modes in a slab waveguide is comparable to that observed for BSWs. At the same time, we demonstrate that, if one is interested in maximizing the electromagnetic energy density at a generic point of a dielectric planar structure, BSWs are often preferable to modes in which light is confined uniquely by total internal reflection. Since these results are wavelength independent and have been obtained by considering a very wide range of refractive indices of the structure constituent materials, we believe they can prove helpful in the design of future structures for the control and the enhancement of the light-matter interaction.

Combination prism array for focusing light

Abstract: A beam deflection device includes two arrays of prisms. The prisms in the first array of prisms have an apex angle below a critical angle such that light passes through the prism and is deflected at an angle below a specified angle. The prisms in the second array of prisms have an apex angle above the critical angle such that light that enters the prism will reflect off the apex surface to an exit surface, resulting in the light being deflected at an angle above the specified angle. In some embodiments, the prisms in the first array and the second array work in conjunction to direct light from multiple locations to a single focal point.

Selective scattering polymer dispersed liquid crystal film for light enhancement of organic light emitting diode.

Abstract: We developed a novel light enhancing film for an organic light emitting diode (OLED) based on polymer dispersed liquid crystal (PDLC). In the film, the liquid crystal droplets are unidirectionally aligned along the film normal direction and exhibit selective scattering. The film scatters light emitted only in directions with large incident angles but not light emitted in directions with small incident angles. When the light is scattered, it changes propagation direction and exits the OLED. The PDLC film reduces the total internal reflection and thus can significantly increase the light efficiency of the OLED.

Measuring thin films using quantitative frustrated total internal reflection (FTIR).

Abstract: In the study of interactions between liquids and solids, an accurate measurement of the film thickness between the two media is essential to study the dynamics. As interferometry is restricted by the wavelength of the light source used, recent studies of thinner films have prompted the use of frustrated total internal reflection (FTIR). In many studies the assumption of a simple exponential decay of the intensity with film thickness was used. In the present study we highlight that this model does not satisfy the Fresnel equations and thus gives an underestimation of the films. We show that the multiple reflections and transmissions at both the upper and the lower interfaces of the film must be taken into account to accurately describe the measured intensity. In order to quantitatively validate the FTIR technique, we measured the film thickness of the air gap between a convex lens of known geometry and a flat surface and obtain excellent agreement. Furthermore, we also found that we can accurately measure the elastic deformations of the lens under loads by comparing them with the results of the Herzian theory.

Coupling Light Emitting Diodes with Photocatalyst-Coated Optical Fibers Improves Quantum Yield of Pollutant Oxidation.

Abstract: A photocatalyst-coated optical fiber was coupled with a 318 nm ultraviolet-A light emitting diode, which activated the photocatalysts by interfacial photon-electron excitation while minimizing photonic energy losses due to conventional photocatalytic barriers. The light delivery mechanism was explored via modeling of evanescent wave energy produced upon total internal reflection and photon refraction into the TiO2 surface coating. This work explores aqueous phase LED-irradiated optical fibers for treating organic pollutants and for the first time proposes a dual-mechanistic approach to light delivery and photocatalytic performance. Degradation of a probe organic pollutant was evaluated as a function of optical fiber coating thickness, fiber length, and photocatalyst attachment method and compared against the performance of an equivalent catalyst mass in a completely mixed slurry reactor. Measured and simulated photon fluence through the optical fibers decreased as a function of fiber length, coating thick...

Electrochemical ATR-SEIRAS Using Low-Cost, Micromachined Si Wafers.

Abstract: Thin, micromachined Si wafers, designed as internal reflection elements (IREs) for attenuated total reflectance infrared spectroscopy, are adapted to serve as substrates for electrochemical ATR surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). The 500 μm thick wafer IREs with groove angles of 35° are significantly more transparent at long mid-IR wavelengths as compared to conventional large Si hemisphere IREs. The appeal of greater transparency is mitigated by smaller optical throughput at larger grazing angles and steeper angles of incidence at the reflecting plane that reduce the enhancement factor. Through use of the potential dependent adsorption of 4-methoxypyridine (MOP) as a test system, the microgroove IRE is shown to provide relatively strong electrochemical ATR-SEIRAS responses when the angle of incident radiation is between 50 and 55°, corresponding to refracted angles through the crystal of ∼40°. The higher than expected enhancement is attributed to attenuation of the reflection ...

Directional outcoupling of photoluminescence from Eu(III)-complex thin films by plasmonic array

Abstract: A plasmonic array, consisting of metallic nanocylinders periodically arranged with a pitch comparable to the optical wavelength, is a system in which both the localized surface plasmon polaritons (SPPs) and diffraction in the plane of the array are simultaneously excitable. When combined with a phosphor film, the array acts as a photoluminescence (PL) director and enhancer. Since the array can modify both excitation and emission processes, the overall modification mechanism is generally complex and difficult to understand. Here, we examined the mechanism by simplifying the discussion using an emitter with a high quantum yield, large Stokes shift, and long PL lifetime. Directional PL enhancement as large as five-fold occurred, which is mainly caused by outcoupling, i.e., the PL trapped in the emitter film by total internal reflection is extracted into free space through the SPPs and diffraction. The present scheme is robust and applicable to arbitrary emitters, and it is useful for designing compact and ef...

Magnetic control of Goos-Hänchen shifts in a yttrium-iron-garnet film.

Abstract: We investigate the Goos-Hanchen (GH) shifts reflected and transmitted by a yttrium-iron-garnet (YIG) film for both normal and oblique incidence. It is found that the nonreciprocity effect of the MO material does not only result in a nonvanishing reflected shift at normal incidence, but also leads to a slab-thickness-independent term which breaks the symmetry between the reflected and transmitted shifts at oblique incidence. The asymptotic behaviors of the normal-incidence reflected shift are obtained in the vicinity of two characteristic frequencies corresponding to a minimum reflectivity and a total reflection, respectively. Moreover, the coexistence of two types of negative-reflected-shift (NRS) at oblique incidence is discussed. We show that the reversal of the shifts from positive to negative values can be realized by tuning the magnitude of applied magnetic field, the frequency of incident wave and the slab thickness as well as the incident angle. In addition, we further investigate two special cases for practical purposes: the reflected shift with a total reflection and the transmitted shift with a total transmission. Numerical simulations are also performed to verify our analytical results.

An array fluorescent biosensor based on planar waveguide for multi-analyte determination in water samples

Abstract: A planar waveguide-based array immunosensor (PWAI) was described, allowing measurements of up to twenty-four analytes in eight separate channels rapidly, sensitively and simultaneously. In this system, a linear laser light created by a line generator was coupled into a planar optical waveguide via a beveled angle, forming eight individual total internal reflection (TIR) lines. A multi-channel microfluidics cell was employed to isolate the parallel TIR lines physically so as to form eight independent flow channels on the same chip, avoiding the cross-reactivity of antibodies and supporting various bioassay conditions. By employing fluorescent detection with fluorophore-labeled antibodies binding to the surface of the waveguide with the analyte derivative covalently attached, the array immunoassays can realize the multi-analyte biosensing. A model was proposed to guide the design of such a planar waveguide-based evanescent wave biosensor. The proposed system was confirmed with the comparable sensitivity with previously reported waveguide biosensor. In addition to being a multi-channel analytical device for the highly sensitive detection of contaminants, the proposed evanescent wave PWAI can provide the dynamic surface-based biomolecular interaction information regarding the affinity and kinetics with high sensitivity.