Enhanced slow light in microfiber double-knot resonator with a Sagnac loop reflector

We propose a theoretical model to describe the light-propagation property of the microfiber double-knot resonator with a Sagnac loop reflector. The mathematical relationships between the reflection light field and the input one of this structure are deduced. Numerical simulations indicate that, comparing with the group time delay in the microfiber double-knot resonator, the one in the same resonator but with a Sagnac loop reflector can be enhanced considerably. For comparison, microfiber double-knot resonators with and without a Sagnac loop reflector are both fabricated. Corresponding comparison experiments are performed, which indeed demonstrates the theoretical prediction. A group time delay of about 61 ps is achieved experimentally in the resonator with a Sagnac loop reflector, while in the same resonator but without a Sagnac loop reflector it is only about 30 ps.