Abstract
This study experimentally demonstrates a broadband (20%) superluminality in a Fabry-Pérot-like interferometer implemented on a waveguide system. A narrow wave packet propagating with an efrective group velocity of 5.29 +4.28 -1.70 c without distortion was observed. The underlying mechanism is attributed to the multiple-reflection interference and the modal efrect, which provide an approach for controlling the wave characteristics through manipulating the geometry of the system. Besides, the criteria of the renowned generalized Hartman effect are explicitly clarified.