Device and method for reducing outgoing mode field diameter based on femtosecond laser direct-writing transparent material optical waveguide

A device for reducing the outgoing mode field diameter based on a femtosecond laser direct-writing transparent material optical waveguide comprises a femtosecond laser, an attenuator, an optical shutter, a spatial light modulator, a first reflecting mirror, a first convex lens, a slit, a second reflecting mirror, a second convex lens, a chromatic beam splitter, a microscopic objective, a transparent material, a three-dimensional translation stage, a computer, a cold light source, a third reflecting mirror and a charge coupled device (CCD). The invention discloses a method for reducing the outgoing mode field diameter based on the femtosecond laser direct-writing transparent material optical waveguide. With the device and the method, on the basis of the femtosecond laser direct-writing optical waveguide, the size of an outgoing mode field can be adjusted on the premise of low coupling loss. The method has the great significance in transforming of a silicon-based waveguide mode field with the relatively small size into a mode field of a standard single-mode fiber in integrated optics.