Waveguide mode

Figure 10-11. The sample is a 290 nm thin film of LPPP deposited on a BK7 substrate. A planar waveguide glass/polymer/air is formed since the polymer film has the highest index of refraction. The resulting intensity profile of the guided TE waveguide mode for the sample is shown on the right hand side. Only one guided mode is supported.

Since the confined modes (whether they are waveguide modes or surface plasmons) are nonradiative (i.e., their wavevector parallel to the interface, is greater than the wavevector of the... 

Figure 7. Field distribution for the n = / and n -2 TE waveguide mode for an air-PDA film-silver system for npda = 1.51, d = 5500 A and a Drude-model metal.

The two important properties of the waveguide mode are its cross-sectional electric field amplitude profile A(x,y) and the effective index /VelT. Here x and y are the coordinates in the plane perpendicular to z, the waveguide propagation direction. The electric field at any point along the waveguide is given by... 

Evanescent Waves of Guided and Leaky Waveguide Modes... 

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. 

Fig. 15.2 Illustration of (a) guided waveguide modes and (b) leaky waveguide modes in a three layered waveguide structure...

In Sect. 15.2 we concluded that refractive index variation in the aqueous cover media shifts the effective refractive index of the waveguide modes. Thus, by monitoring on-line the effective refractive index, the refractive index change can be followed. This is the basic principle of waveguide sensing. 

For waveguide modes in a pure dielectric structure, Nm is nmax = Max c, ns at dF = (/cutoff and nF at dF > oo. The so-called cut off thickness, (/cutoff is defined as the film thickness at which the field s propagation angle in the film gets... 

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