Accurate frequency-tuning mechanism from a wedge prism in a single-mode tunable laser.

We present a new, accurate frequency-tuning mechanism in a grazing-incidence cavity for singlelongitudinal-mode oscillation in a tunable laser. A wedge prism with a small apex angle is inserted between the tuning mirror and the grating for accurate frequency tuning. In this configuration, the laser frequency can be tuned precisely by rotation of the wedge instead of the tuning mirror. This fine-tuning mechanism offers the ability to tune the frequency over more than 400 GHz without mode hop and with a tuning accuracy that is 2 orders of magnitude larger than that of conventional tuning methods.