2.1 Symmetric Planar Slab
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A. Waveguide Condition
1. Light field penetrates into cladding
(evanescent wave).
2. Light field decays along y-direction
(Gaussian intensity distribution).
3. Higher order of m shows more light
fields in cladding (modes).
4. Smaller represents larger m (higher
i
mode in cladding more).
5. Modes travel with different vg.
6. Modes integrate up as a spread group.

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