Coherent control of multiple quantum well active photonic band gaps via infrared dressing of super-radiant excitons

摘要

Optical responses of active multi-quantum well photonic band gap structures are mostly determined by the excitonic effects (superradiant excitons) and the contrast between the background refractive indices of the wells and barriers (nonresonant effects). Recently we studied coherent control of such photonic band gaps via infrared dressing of the superradiant excitons. This was done considering an infrared laser field near resonantly coupled such excitons with the excitons associated with the second conduction subbands of the quantum wells. This led to the formation of photonic electromagnetically induced transparency and disentanglement of the excitonic contributions from those associated with the nonresonant effects via destruction of the superradiant modes. Here we study how such a disentanglement process dramatically changes transmissions of the Bragg multiquantum well structures. In particular, we show that when the infrared laser intensity is high, the non-resonant effects form an incomplete passive band gap around the Bragg wavelength. Such a band gap, which is immune against the infrared laser, is flanked by two non-photonic gaps (absorption peaks). These peaks are associated with the large absorption of two dressed exciton states, i.e., Aulter-Townes doublet. Any variation in the intensity of the infrared laser changes the wavelengths of these peaks, making them closer or farther to the passive photonic band gap.