External cavity, continuously tunable wavelength source

摘要

An external cavity, continuously tunable wavelength source comprising a coherent light source having an external cavity including a reflector, such as a mirror or right-angle prism, for reflecting a selected wavelength from a diffraction grating back into the coherent light source. The wavelength is selected by simultaneous rotation and linear translation of the reflector about a pivot point such that the optical path length of the external cavity is substantially identical to a numerical integer of half wavelengths at a plurality of tunable wavelengths about a central wavelength of a tunable bandwidth for the source such that cavity phase error is zero at the central wavelength and is maximally flat on either side of the center wavelength within the tunable bandwidth. The location of said pivot axis is chosen to set the cavity phase error equal to zero and its first and second derivatives substantially equal to zero at exactly one wavelength. The external cavity may be either a Littman optical cavity configuration or a Littrow external cavity configuration. The output of the coherent light source is optically coupled to a gain element for amplification.