1,720,995 research outputs found
Waveguide surface plasmon resonance sensors
No full textPlanar waveguide surface plasmon resonance sensors have great potential for use in the field of environmental monitoring. In this paper we present a rigorous model for the optical power transmittance of this type of sensor. This model is used to determine the change in transmitted power when a thin layer is adsorbed to the metal-clad region of the sensor, as a function of the waveguide and metal film parameters. Design curves for sensors based upon glass waveguides coated with thin gold films immersed in water are presented. Experimentally determined changes in the output power of a waveguide surface plasmon sensor, as a function of the length of the gold film, are presented and compared to theory
Waveguide surface plasmon resonance sensors
No full textGuided-wave optical biosensors have great potential for use in the field of environmental monitoring. In particular, planar waveguide technologies offer the possibility of producing compact, monolithic, multisensor devices which may be connected to instrumentation using optical fibres, allowing remote operation. Optical evanescent field sensing techniques presently under investigation include grating couplers, waveguide interferometers and surface plasmon resonance (SPR) sensors. In the latter case, the surface plasmon is generally excited using a "bulk" optical component such as a prism, and equipment using this technique is now commercially available. One potential advantage of the SPR technique is that the metal film which supports the surface plasmon may also be used as an electrode for electrochemical control of sensing reactions. However, recent reports have indicated that the "bulk" SPR devices may not ultimately be as sensitive as fully guided-wave approaches such as the Mach-Zehnder interferometer. An alternative to the "bulk" SPR devices which has recently emerged is the use of distributed coupling between a dielectric waveguide and the surface plasmon mode in a metal-coated waveguide. This has the advantage of combining greater design flexibility and the potential for monolithic integration with the well-established technique of SPR. However, at present no adequate model for the performance of these devices exists. ..
Sensitivity enhancement of integrated optical sensors by use of thin high-index films
No full textThe proportion of power carried in the superstrate medium by the guided modes of integrated optical waveguides can be increased by the addition of a thin high index film. Enhanced refractive index sensing is demonstrated using channel waveguide Mach-Zehnder interferometers with Ta2O5 overlayers. Sensitivity increases by a factor greater than 50, and a detection limit better than 5x10-7 are obtained. This approach is broadly applicable to sensing at waveguide surfaces where the strength of evanescent fields dictates performance
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
Sensitivity enhancement of integrated optics sensors by thin high index films
No full textExperimental measurements on waveguide Mach-Zehnder interferometers are presented which show that order of magnitude improvements in the sensitivity of planar waveguide sensors can be achieved by incorporating thin high index overlays
Optical biosensor techniques for monitoring organic pollutants in the aquatic environment
No full textThe principal contribution of Southampton University to the BIOPTICAS project is in the realization of planar optical waveguide probes to determine the optical properties of attached sensing films. Three types of device are being investigated: surface plasmon resonance (SPR), directional coupler and chemiluminescence sensors. Techniques have been established for the deposition of compatible electrodes for electrochemical modulation of sensing reactions as an integral part of devices, and equipment has been set up for the fabrication of waveguides in glass substrates by field-assisted ion-exchange. The modelling and design stages for the devices are now close to completion, and we have begun the fabrication and evaluation of preliminary designs and verification of models. Interaction with partners has resulted in the establishment of standardised sensor chip formals and plans for comparative evaluations of the sensors developed in the project, using standardised sensing reactions are well in hand
Waveguide surface plasmon resonance studies of surface reactions on gold electrodes
No full textWe describe the fabrication and characterisation of gold-coated graded index channel waveguide sensors designed for simultaneous electrochemical and surface plasmon resonance studies. The active sensing electrode area is a thin gold film between 0.5 and 5 mm in length and 200 µm wide deposited on top of a 3 µm wide waveguide which forms one arm of a Y-junction while the other arm of the Y-junction serves as a reference. Using these devices we have measured simultaneously the changes in transmittance through the device whilst carrying out cyclic voltammetry in either sulfuric or perchloric acid solution or during the deposition of an UPD layer of copper at the gold surface. In all cases we obtain stable and reproducible results which demonstrate the very high sensitivity of the devices to sub-monolayer changes occurring at the gold electrode surface. The response of these integrated optoelectrochemical devices is discussed in terms of a numerical model for the propagation of light within the waveguide structure
Underpotential deposition of a copper monolayer on a gold film sensed by integrated optical surface plasmon resonance
No full textAn integrated optical surface plasmon resonance sensor combined with electrochemical control is used to monitor the underpotential deposition of a copper monolayer onto a gold film from 1 mM Cu2+ in 0.1 M perchloric acid
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
A polarised brightness-enhanced Nd:Y<sub>3</sub>Al5O<sub>12</sub> planar waveguide laser
No full textA simple method for the production of a polarised Nd:Y3Al5O12 on Y3Al5O12 planar waveguide laser is reported. A 50nm layer of Au deposited on the surface of an unclad, 8.3 µm thick core region has produced an improvement in the TE/TM polarisation extinction ratio from 7dB to 27dB. The M2 of the beam in the guided plane has been reduced from 1.53 ±0.04 in an uncoated region of the waveguide to 1.17 ±0.01 in the Au coated region using optimum pump launch conditions
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