Optical gain enhancement in PBG structure with active n-i-p-i superlattice

In a certain spectral range the extinction coefficient K in n-i-p-i layers becomes negative at the high excitation levels. It results in the appearance of the light amplification. The extinction coefficient in n-i-p-i layers depends on the wavelength and the difference in the quasi-Fermi levels /spl Delta/F. We considered the model, when a pump, which can be electrical as well as optical, excites uniformly all active layers and calculated light transmission characteristics versus /spl Delta/F which is the same within all active layers. In the present work we consider the optical mechanism of the pump, and solve the nonlinear problem of the pump light propagation through the photonic band gap (PBG) structure and the linear problem of a probe light transmission through the same structure with excited active layers.