  We have experimentally investigated the fluxon dynamics in a narrow
Bi2Sr2CaCu2O8+d stack with junction length L~1.8 um. As an evidence of
high-frequency excitation by a collective cavity mode, under an (in-plane)
external magnetic field, the current-voltage characteristics show prominent
Fiske steps with the corresponding resonance frequencies of 75-305 GHz. Further
study of flux-flow resistance oscillation with various c-axis currents
clarifies the correlation with Fiske steps by distinguishing two different
regions i.e., static flux-flow region at low bias current level and dynamic
Fiske step region at high bias current level.
