The invention relates to the technical field of
semiconductor lasers, in particular to an ultra-narrow linewidth
wavelength-adjustable
external cavity laser based on a planar
metal grating, which comprises a
gain chip, and the left end face and the right end face of the
gain chip are respectively plated with a high reflection film and a first antireflection film; a planar
metal grating waveguide is arranged on the right side of the
gain chip, the right end face of the gain chip is aligned and attached to the left end face of the planar
metal grating waveguide, and a second antireflection film and a third antireflection film are plated on the left end face and the right end face of the planar
metal grating waveguide respectively; the planar
metal grating waveguide comprises a grating waveguide substrate, a
ridge optical waveguide is arranged on the upper portion of the grating waveguide substrate, an annular
resonance optical waveguide is arranged on the front side of the
ridge optical waveguide, a planar
metal grating is arranged on the upper portion of the
ridge optical waveguide, and a top covering layer is arranged on the upper portion of the planar metal grating. Through the
centimeter-level metal grating and the low-loss
coupling structure,
light beam quality with 3dB
line width less than 700Hz and M2 less than 0.9 is realized.