Planar waveguides multimode

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. 

Ross SE, Seliskar CJ et al (2000) Spectroelectrochemical sensing based on multimode selectivity simultaneously achievable in a single device. 9. Incorporation of planar waveguide technology. Anal Chem 72 5549-5555... 

When the gain medium incorporating nanoparticles is deposited onto glass substrates defining a planar asymmetric slab waveguide, multimode laser emission can appear without the need of the presence of any resonant substructure. 

It is harder to count the number of bound mode solutions for the fiber, than it is for the planar waveguide, because the roots of the eigenvalue equations in Table 12-4(a) are now not uniformly spaced, even at cutoff. However, we show in Section 36-13 that, provided the fiber is multimoded with 1, My = Int the smallest integer just exceeding F /2. 

The attenuation of leaky rays on multimode fibers is discussed in Section 7-1. For higher-order modes, it is intuitive that there should be good agreement between the leaky-mode and corresponding leaky-ray attenuation coefficients. We discuss this agreement both qualitatively and quantitatively in Section 36-11 for step-profile planar waveguides and fibers. 

For modes which propagate only on the planar waveguide when it is multimoded, Vp 1, and the term involving s in Eq. (36-29) can be neglected, provided 6 0. ... 

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