Question

Explain why it is easier to make a single-mode waveguide in a symmetric three-layer waveguide than it is in an asymmetric three-layer waveguide.

Answer 1

It is easier to make a single-mode waveguide in a symmetric three-layer waveguide than it is in an asymmetric three layer waveguide because, In a symmetric three layer waveguide there is no cut off required for propagation of the lowest order mode and it does not matter how thin the waveguiding layer is made, and this is why the thickness can be reduced to whatever is required to cut off all higher order modes and the lowest order mode will still propagate but In an asymmetric three layer waveguide there is a minimum cutoff thickness even for the lowest-order mode, this is why It is easier to make a single mode waveguide in a symmetric three layer waveguide than it is in an asymmetric three layer waveguide.

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