Improving the Raman amplifier bandwidth and gain using multi-micro ring photonic crystal structures

In this paper, first the improvement in the Raman amplification bandwidth through the self-phase modulation (SPM) effect in the straight photonic crystal structures was compared to the single-ring and 2-ring photonic crystal structures. The resonance effect in micro ring structures, enhances the effective pump power and thus can achieve the same level of Raman gain at a much lower input pump power, but an increase in the amplification bandwidth in a ring structure is limited by the filtering effect of the micro ring. Then, in order to increase the Raman amplification bandwidth and gain, a 10-ring new structure was introduced. The design of this new structure is based on the use of optofluidic materials. To model Raman amplification in these structures, Maxwell equations are solved using finite difference time domain method considering optical nonlinear parameters like two photon absorption, free carrier absorption, Kerr effect and self-phase modulation effect. This multi-ring Raman amplifier yields a large Raman gain (26.79 dB) and a considerable Raman amplification bandwidth (10.33 mm) despite its extremely short amplification length (160 μm) and an extremely low input pump power (0.5 W).