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Let us talk about Photonic crystals and photonic bandgap
Photonic crystals are a class of periodic nanostructure with periodic dielectric indices. Light interaction with the photonic crystal cause a few forbidden frequency intervals to appear in the transmission spectrum which are named as photonic bandgaps.
We know that Schrodinger equation describe the flow of electron in a periodic potential. Such as the flow of electron in a semiconductor.
If we analyze the electromagnetic wave equation in the same way, we get bands. We can control the EM wave in these periodic structures the same way we control electroncs in silicon (the semiconductor). So like electron band we have photonic band. In analogy with the band diagram, we call this photonic band diagram.
In the Photonic band gap (Forbidden energy): photonic crystal act like an insulator and act like a mirror. They reflect light.
Optical waves with frequency equal to the photonic bandgap cannot propagate in the forward direction and thus gets reflected in the backward direction. The reflected components can be treated as a stop band filter in the optical communication
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IEEE/ICACT20220296 Slide.04
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