Patent ID: 7916763

Claim:
A wavelength tunable system comprising: a laser having a laser diode cavity and an external cavity, the cavities having a common optical axis, the laser diode cavity and the external cavity being mode-matched such that the optical path length of the external cavity is an integer multiple of the optical path length of the laser diode cavity and the external cavity includes a first set of modes corresponding to modes of the laser diode cavity and a second set of modes offset from the first set of modes by less than a spacing of the laser diode cavity modes; a frequency-adjuster in the external cavity to spatially separate the frequency components of incident light and to select frequency components for feed-back into the laser diode cavity; and an adjustable current source to adjust the laser diode current to a discrete set of different bias values to shift the modes of the laser diode cavity into alignment with the second set of modes.