Single-mode-frequency-tuning of an ECDL in Littrow configuration using an acousto-optic-modulator (AOM)

Conventional Littrow-laser use a reflection grating as a frequency selective element. The selective frequency can be varied turning the grating using a piezo actuator. A well done choice of the turning point leads to a theoretically unlimited single mode frequency tuning range. The tuning velocity is restricted by the piezo-grating-system inertia. To avoid this disadvantage we survey possibilities to change the angle between the laser beam and Litrow grating, that is the grating selectivity with an AOM. The result of our calculations is that a special passive optical element needs to be placed in the optical path to keep the cavity mode entrainment. Due to the absent of moving mechanical items a rapid single mode tuning velocity combined with a large frequency range can be realized with such a configuration.