1,720,977 research outputs found
Determination of complex refractive indices of absorbing media using a directional coupler
No full textA method is presented for the simultaneous measurement of the real and imaginary parts of the refractive indices of absorbing media using an integrated-optical sensor
Directional coupler sensor using a low-index fluoropolymer isolation layer
No full textA novel integrated optical sensor based on an asymmetric directional coupler structure is described. A patterned low-index fluoropolymer film is used to define the sensing region. The response of the device with respect to small changes in refractive index is demonstrated, and its potential for detecting antibody-antigen reactions is considered
Integrated optical sensor utilising a 1D CCD array for multiple output addressing
No full textAn inexpensive and robust method for acquiring multiple outputs from integrated optical sensor devices using a 1D CCD array is described in this paper. An example is given of the development of an instrument based on the use of an integrated optical Mach-Zehnder interferometer (MZI) refractive index transducer. The technique is especially promising for application to multianalyte sensors where several outputs need to be interrogated simultaneously. The high sensitivity and low noise demonstrated by the system will enable the use of cheap, stable LED light sources in practical instruments. Introduction: Integrated optical transducers for the real-time measurement of interactions between biological molecules and for the specific detection of chemical and biochemical species are the subject of growing interest. Applications of this technology include environmental pollution monitoring, industrial process control and medical diagnostics. Integrated optical sensors provide the high detection sensitivity achievable using optical transduction techniques in a compact and robust format. This approach also offers advantages for the fabrication of multianalyte sensors through the integration of multiple transducers on a single chip by straightforward scaling of the photolithographic production process. Several types of integrated optical sensor have been described (e.g. [1-3]), but no commercially viable multianalyte system currently exists and, in order to fully exploit this technology in practical instrumentation, inexpensive and reliable techniques for addressing the multiple outputs of waveguide devices must be found. Fibre-to-chip pigtailing of integrated optical devices formed in 'passive' materials such as glass, where it is difficult to truly integrate monolithic light sources and detectors, is not the best solution when dealing with multiple outputs due to the necessity of producing and pigtailing fibre arrays. For single input devices, however, fibre input coupling is still a viable option as only a single pigtail needs to be made. In this paper we present measurements on multiple-output integrated optical sensor devices using fibre input coupling and a cheap, readily available, 1D CCD array detector to simultaneously address all outputs. A lens is used to focus the waveguide outputs onto the array, resulting in a compact unit that can be housed in a standard instrument package. A further advantage of this arrangement is that other optical elements such as filters and polarisers can readily be inserted into the beam path
Forces on a Rayleigh particle in the cover region of a planar waveguide
No full textWe report on the optimization of a waveguide structure for the maximization of the radiation forces exerted on a Rayleigh particle in the cover region. The two main radiation forces involved are the transverse gradient force which attracts a particle into the waveguide and the combined scattering and dissipative forces which drive the particle forward along the channel. The dependence of these forces on parameters including the incident wavelength, the surrounding medium embedding the particles, and the polarizability of the particles is discussed. Both dielectric and metallic gold spheres of radius 10 nm are considered in the model. Special emphasis is devoted to the maximization of the transverse gradient force due to the optical intensity gradient at the waveguide surface, and the wavelength dependence of the polarizability of gold nanoparticles
Detection of glucose via electrochemiluminescence in a thin-layer cell with a planar optical waveguide
No full textLight generated by luminol electrochemiluminescence is coupled into a simple planar optical waveguide and is collected with a photomultiplier tube and a photon counter unit. The waveguide is mounted to a thin-layer cell which is connected to a flow injection analysis system. The waveguide is coated with indium tin oxide and modified with covalently attached glucose oxidase. The range of detection for glucose is 0-10 mM (correlation coefficient r = 0.9974), with a detection limit of 0.3 mM
Optoelectrochemical sensor for lead based on electrochemically-assisted solvent extraction
No full textA thin film containing the complexing agent 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol (BrPADAP) deposited on the surface of an indium tin oxide (ITO) electrode has been used as a colorimetric sensor for lead. The sensor is based on a new electrochemically assisted solvent extraction method. When a cathodic potential was applied to the thin-film sensing layer, lead ions were extracted from the aqueous solution into the film resulting in an increase of absorbance at 550 nm. The magnitude of the absorbance change was linearly dependent on the concentration of lead in the range 0–5 ppm with an estimated limit of detection for a simple spectrophotometric method better than 250 ppb. The sensor was reset for a fresh measurement by applying an anodic potential. The prospects for using this electroassisted extraction method in conjunction with the optical waveguide evanescent field detection as a new integrated sensor for trace analysis are discussed. A sensitivity better than 10 ppb is predicted for this configuration
Waveguide surface plasmon resonance biosensor for the aqueous environment
No full textWe report the fabrication and performance of gold coated waveguide surface plasmon resonance biosensors. Biotin-avidin binding reactions at the sensor surface were observed. The output power of the sensor showed a decrease of 32% on binding a dual layer of biotin-avidin
Propulsion of gold nanoparticles on optical waveguides
No full textThe optimization of potassium ion-exchanged optical waveguides in glass for evanescent field propulsion of colloidal gold nanoparticles is reported. Velocity dependence upon ion-exchange parameters is given and a maximum velocity of 8 m/s was achieved for 10–40 nm radius particles with 500 mW modal power at 1.047 µm. <br/
Integrated optical dual Mach-Zehnder interferometer sensor
No full textThe fabrication and operation of robust integrated optical refractometers, suitable for precise measurements of small changes without ambiguity over a wide range of refractive indices, is described. The design primarily uses an optical fibre coupled dual-sensitivity integrated optical Mach-Zehnder Interferometer sensor chip incorporating 3x3 directional coupler combiners and internal referencing. High-index Ta2O5 films were deposited on the waveguide surface in order to increase sensitivity and measurements of their response to liquid analyte index have been carried out by passing aqueous sucrose solutions over the sensor surface. These devices are intended for application as high-sensitivity multi-purpose chemical sensors and biosensors
Manipulation of colloidal gold nanoparticles in the evanescent field of a channel waveguide
No full textColloidal gold spheres of radius 10 nm are reported to move forward in water, under the influence of radiation pressure forces, due to the evanescent field at the surface of an optical channel waveguide. The velocity is linearly dependent upon the optical power in the waveguide, acquiring a maximum velocity of 4 µm/s for modal power of 500 mW in the TM polarization at a wavelength of = 1.047 µm
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