External cavity tunable semiconductor laser

The invention provides an external cavity tunable semiconductor laser. The external cavity tunable semiconductor laser comprises a gain module, an optical switch module and an optical mode selection module. The gain module comprises a plurality of gain chips, the gain chips are suitable for providing initial laser, and the gain spectrum coverage ranges of the plurality of gain chips are not overlapped so as to enlarge the gain bandwidth of the initial laser; the optical switch module is suitable for splitting the initial laser, so that the split laser is output by the multi-path output port; and the light mode selection module comprises a plurality of mode selection assemblies, the plurality of mode selection assemblies are respectively suitable for selectively outputting multiple paths of output laser based on the beam splitting laser and obtaining feedback light based on the output laser, and each path of output laser has a specific wavelength so as to output tunable narrow linewidth laser in a wavelength r