Sensors planar waveguide

A novel fiber optic sensor concept using antibody-antigen reactions at a glass-liquid interface was reported by Daehne146. The reaction of antibodies immobilized onto the surface of fused silica fiber optic or planar waveguides with antigens in solution was detected by interaction with the evanescent wave. By detecting in-line fluorescence, the measurement of human IgG is described. 

In addition, the integration of modem optical technology and electrochemical techniques for sensing applications appears to be a powerful new approach. A new type of optoelectrochemical sensor for chlorine, based on an electrochromic thin-film sensing layer placed on top of a planar waveguide, has demonstrated the applicability of this combined approach. 

The absorption-based platforms described previously employed evanescent wave interrogation of a thin sensing layer coated onto a planar waveguide. A sensitivity enhancement strategy for optical absorption-based sensors based on planar, multimode waveguides was developed recently by us18. The objective was to apply this theory to the development of low-cost, robust and potentially mass-producible sensor platforms and the following section outlines the assumptions and predictions of this theoretical model. 

While planar optical sensors exist in various forms, the focus of this chapter has been on planar waveguide-based platforms that employ evanescent wave effects as the basis for sensing. The advantages of evanescent wave interrogation of thin film optical sensors have been discussed for both optical absorption and fluorescence-based sensors. These include the ability to increase device sensitivity without adversely affecting response time in the case of absorption-based platforms and the surface-specific excitation of fluorescence for optical biosensors, the latter being made possible by the tuneable nature of the evanescent field penetration depth. 

Deposition of sensor layers is possible on fibre Flow-through cell allowing the optics, planar waveguides, and test strips simultaneous exposure of the membrane to... 

Fig. 13.2 Different types of evanescent sensors, (a) a planar waveguide (b) a polished optical fiber (c) an MNF taper...

Luminescent evanescent wave-based sensors use optical fibers and planar waveguides [105,106] as fight-guiding structures, and they are more complex than the absorbance ones. However, such optodes have been satisfactorily applied to measure fluorescence of indicators or labels for the measurement of gas molecules, proteins or labeled antigen-antibody interactions as well as directly in solution [24,107] when immobilized in matrices [23,109]. 

Absorbance evanescent-based sensors are based on the absorption or dispersion of light outside the core. They rely on light attenuation in the evanescent field following the Beer-Lambert law (ATR sensors), but owing to the low intensity of the field, they offer poor sensitivity. This can be improved because the effective optical path length can be increased, especially when using optical fibers, capillary [62] or planar waveguides [114]. 

They are technologically easier to construct than conventional planar waveguides and the fabrication processes are more economic and rugged. Conventional waveguides need thicker substrates (10 times thicker) than ARROW structures to reach equivalent losses in this layer. Moreover, they are less suitable to develop optical sensors based on the core propagation, because if the membrane refractive index was the same, a thickness of about 100 nm would be needed to achieve single-mode behavior in the transversal direction to the layers. ARROWS have a 4-pm-thick core,... 

Duveneck GL, Pawlak M, Neuschafer D et al (1997) Novel bioaffinity sensors for trace analysis based on luminescence excitation by planar waveguides. Sensors Actuators B Chem... 

Lukosz W, Nellen PM, Stamm C, Weiss P (1990) Output grating couplers on planar waveguides as integrated optical chemical sensors. Sensors Actuators B Chem 1 585-588... 

We have divided the book into two volumes comprising six parts. Volume I has two parts and Volume II has four parts. Volume I covers the planar-waveguide and plasmonic platforms. Volume II covers waveguide sensors with periodic structures, optical fiber sensors, hollow-waveguide and microresonator sensors, and finally tetrahertz biosensing. 

Recently, a commercial biosensor device based on interferometry (Ana-light Bio200) produced using planar waveguides was introduced by the company Farfield sensors [61],... 

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