Ultra-narrow linewidth sweep frequency laser

The invention provides an ultra-narrow linewidth sweep frequency laser, which comprises an outer cavity, an optical path device and a control system, and is characterized in that the optical path device is arranged in the outer cavity and comprises a semiconductor gain chip, an aspherical lens, an etalon, a single-fiber coupler, a double-fiber coupler, a transmission grating and an MEMS reflector which are arranged in sequence, and further comprises an optical waveguide coupler; the semiconductor gain chip emits divergent laser; carrying out beam shrinkage and collimation through an aspherical lens, and carrying out frequency spectrum selection through an etalon; the laser beam is converted into an ultra-narrow linewidth collimated laser beam through a single-fiber coupler and a double-fiber coupler; the laser is subjected to specific wavelength selection through the transmission grating and the MEMS reflector to obtain accurate frequency spectrum filtering laser output, and a small part of the laser is refle