Wideband slow light in microfiber double-knot resonator with a parallel structure

The characteristics of slow light in the microfiber double-knot resonator with a parallel structure are investigated both theoretically and experimentally. It is predicted that a wide bandwidth of about 20 GHz and flat-top group delay of about 70 ps can be generated in this resonator by changing the coupling coefficient. In the experiment, such a resonator was fabricated and the slow-light effect was demonstrated. As a result, when a pulse with a bandwidth of 3.35 GHz (equivalent to the temporal width of 299 ps) was launched into the resonator, a large group delay, whose average value was about 69.4 ps with a flat-top wavelength bandwidth of about 190 pm, was achieved.