2.1 Symmetric Planar Slab
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A. Waveguide Condition
1. Light path A B C ...
2. If light has to propagate in
z-direction, wavefront of C
must be in phase with that
of A.
3. When lights are in phase,
they interfere constructively.
4. Light that does not follow 2.
will not propagate long.
k1 is k modified by n :
For constructive interference,
AC

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