Abstract: A tunable laser system includes a plurality of gain media arranged in a plurality of optical paths; an optical device configured to combine optical signals from the gain media into a common optical cavity path shared by the gain media, using at least one optical multiplexing mechanism selected from wavelength-division multiplexing or polarization-division multiplexing; a wavelength-selective tunable filter disposed in the common optical cavity path to select a lasing wavelength; a feedback path configured to return at least a portion of a filtered optical signal from the common optical cavity path to at least one selected gain medium to sustain lasing; and a controller configured to selectively activate at least one gain medium corresponding to the selected lasing wavelength. The plurality of gain media can function as a single effective gain medium providing a tunable wavelength range exceeding that of any individual gain medium among the plurality of gain media.