Abstract: Method and system for generating a sequence of two or more light beam central frequencies. A first mirror, in an optical cavity defined by two or more mirrors, is moved to a sequence of two or more locations relative to a second mirror in the cavity. The first mirror location is dithered relative to the second mirror for each location in the sequence to produce a light beam having a dithered sequence of cavity frequencies that are related to longitudinal mode resonant frequencies for the cavity. Alternatively, frequency locking is implemented for each of the sequence of central frequencies. The light beam may be passed through a sample within the cavity for spectroscopic measurements or may be extracted from an empty cavity to provide a sequence of light beam frequencies for a subsequent application.