The dispersion relation of the optical field close to the photonic band gap in fiber gratings is obtained through theoretical analysis and numerical simulation. The phase velocity, group velocity and group velocity dispersion (GVD) of the transmission pulse are analyzed.
If the periodic structures are fabricated with materials of different dielectric-constants, the photonic band and photonic bandgap may be formed because of the Brag dispersion of the periodic structures to the light wave.
Mechanism of spontaneous radiation relaxation of an impurity atom in a photonic band-gap crystal
A kinetic equation for an impurity atom has been derived, and polarizations of the photonic band-gap crystal and an induced electromagnetic wave at the spontaneous transition frequency due to the suggested mechanism have been investigated.
Under certain conditions this leads to population inversion as a result of an optically allowed transition which does not interact with the coherent pump and at a frequency where no photonic band gaps can exist.
Transmission measurements on the cladding of nanostructured fibers having a form of a two-dimensional periodic structure with a pitch less than 500 nm have revealed the existence of a photonic band gap tunable within the range from 930 to 1030 nm.
Hollow fibers with a two-dimensionally periodic cladding support air-guided modes of electromagnetic radiation due to the high reflectivity of the cladding within photonic band gaps.