  A novel conception of "sensitive mode" (SM) is proposed to apply in
gravitational-wave advanced interferometer configuration. The SM is resonant
oscillation of electromagnetic field in "white-light cavity", where the
resonance line is broadened without decreasing cavity quality. The frequency of
the SM is greatly susceptible to the change of cavity length, and the SM is
established in a cavity with time constant smaller than a conventional mode.
Due to these advantages the sensitivity and bandwidth of AIC can be increased.
