  We report on the controllable response of the lasing frequency to the cavity
round-trip path change. This is achieved by modifying the dispersion of the
intracavity medium in the four-wave mixing regime in Rb. We can either increase
the response by at least a factor of $2.7$ or drastically reduce it. The former
regime is useful for sensitive measurements tracking the cavity round trip
length and the latter regime is useful for precision metrology.
