Evanescent waves waveguide properties

The sensor systems outlined in the present chapter use evanescent electromagnetic radiation to monitor various analytes in aqueous solutions. Therefore, as a beginning, the basic properties of evanescent electromagnetic waves and the so-called TIR phenomena are summarized. Afterwards, two types of waveguide modes will be briefly discussed guided and leaky modes, which both generate evanescent waves at a solid/liquid boundary. 

The existence of an evanescent wave was discussed above (cf. Section III), together with PSPs. The optical properties of thicker LBK films can be characterized by the optical waveguide spectroscopy (WGS), and their layered structure can be probed by means of X-ray reflectometry. 

It follows from the definitions above that for measuring the electrooptic coefficients, one should measure the index variation due to the application of an electric field. Evanescent waves coupled by the ATR method to surface plasmons or to waveguide modes have been demonstrated as useful tools for measuring electrooptical properties of NLO Langmuir-Blodgett films and NLO polymers [81-85],... 

The analyte directly affects the optical properties of a waveguide, such as evanescent waves (electromagnetic waves generated in the medium outside the optical waveguide when light is reflected from within) or surface plasmons (resonances induced by an evanescent wave in a thin film deposited on a waveguide surface). 

A photochromic film in a planar waveguide can bind light in a confined manner, allowing the use of evanescent fields as sensitive tools for probing the optical properties of these films. A surface wave that propagates at the interface between an ultrathin photochromic layer, such as a SAM, and a given medium can probe small photochemical changes at this interface. The... 

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