Tunable fast and slow light in a traveling wave microresonator via interaction of intra-cavity backscattering with dual contrapropagating inputs

We present a theoretical investigation on the interplay between the intra-cavity backscattering and the losses out of the cavity when dual contra-propagating inputs are launched into a traveling wave microresonator, which has random surface defects (or backscatters) that are intentionally introduced. By adjusting the amplitude and/or phase differences between the dual inputs, the interaction of the cavity modes with the backscatters can be controlled. Consequently, the transmission and dispersion of the output light can be easily manipulated. This feature makes the dual input scheme highly attractive for continuously tunable fast and slow light applications, particularly if active tuning elements, such as p-i-n diode and heater, are absent in the cavity. Continuous tunability in the group delay of the fast and slow light is also demonstrated at the C-band wavelength of 1.55 mu m. (C) 2010 Optical Society of America