The invention discloses a method for preparing a concave mirror on an optical
waveguide. The method includes following steps: step 1,
cutting the optical
waveguide to form a v-shaped groove by employing a v-shaped
diamond knife, wherein one plane of the v-shaped groove is a 45-degree inclined plane, and the other plane is a
vertical plane; step 2,
etching a cube groove by employing one
vertical plane, close to the v-shaped groove, of an
excimer laser as one side, wherein the width of the cube groove is 2 / 3 or once of the depth of the v-shaped groove, and the depth of the cube groove and the depth of the v-shaped groove are the same; step 3, placing a plate in an inclined manner to enable the inclined plane of the v-shaped groove to be horizontal, and performing
hot working on the inclinedplane of the v-shaped groove by employing a
carbon dioxide laser to enable the inclined plane to be ablated to form a recessed surface; and step 4, plating a high-reflection film on the recessed surface to form the concave mirror. According to the method, based on the fact that the
diamond knife fabricates the 45-degree inclined plane,
hot working is further performed by the inclined plane by employing the
carbon dioxide laser, a
processing process has a thermal annealing effect due to the mechanism of
hot working, and the reflective concave mirror with low roughness can be obtained.