Two orthogonal light polarizations in a waveguide overcoupled to microring resonators can propagate as fast and slow light. Which polarization is fast (slow) is determined by input polarization and the number of resonators.
In the seemingly never-ending quest to speed up data transfer, light constitutes the ultimate communications carrier. However, the speed of light through a medium is generally constant, making photon storage and on-chip optical signal processing difficult tasks to implement. To slow things down, coupling microring resonators to an optical waveguide can effectively delay the propagation of photons. It has also been shown that the dispersion properties of these devices can distort the pulse profile so that the speed of light appears to be exceeded, providing so-called fast-light. From a practical viewpoint, it would be desirable to combine both of these properties in a single optical device. Recent work has found that these microring resonators are birefringent with respect to the polarization of the propagating light; i.e., one polarization simultaneously propagates faster than its orthogonal counterpart. From calculations, Fietz and Shvets show that by using light of mixed polarization and adjusting the mixing angle of that light and the number of microring resonators along the waveguide, a tunable delay time between polarized wave packets of incoming light should be readily achieved. — ISO
We analyze fast- and slow-light transmission in a zigzag microring resonator chain. In the superluminal case, a new light-transmission effect is found whereby the input optical pulse is reproduced in an almost-simultaneous manner at the various system outputs. When the input carrier is tuned to a different frequency, the system permits to slow down the propagating optical signal. Between these two extreme cases, the relative delay can be tuned within a broad range. We propose, and analyze numerically, a laser-array configuration for the stable operation of active devices.
In this paper we demonstrate, how fast and slow light phenomena in ring resonator can simultaneously be observed at a single frequency, using strongly coupled ring resonators. We also report on the design of a ring resonator with SOI technology that operate in optical wavelength 1.55 micron and have (one micro-ring) a factor for fast light ~22 picosecond (ps) and a factor for slow light ~12 ps with bandwidth ~100GHz with mixing angle (θ) 30 degrees, however depended on mixing angle and number of rings. Using light in a mixed polarization state, we show that fast and slow light can be obtained from a single incident wave packet. We simulate one micro-ring and extend our result to more micro-ring.