A wavelength locker includes a first beam splitter positioned in a beam path of an output beam produced by a laser. The first beam splitter splits the output beam into a first beam and a second beam. An interferometric optical element is optically contacted to the first beam splitter. The interferometric optical element receives the second beam from the first beam splitter and generates a third beam with an optical power that varies periodically with wavelength. A second beam splitter is positioned in a beam path of the first beam or in a beam path of an output beam produced by a laser, and creates a fourth beam. A first detector generates a first signal in proportion to an optical power of the third beam. A second detector generates a second signal in proportion to an optical power of the fourth beam. A wavelength of the output beam is adjusted in response to a comparison of the first and second signals and a predetermined reference signal level.