Narrow-linewidth excimer laser with improved resonant cavity

The invention discloses an excimer laser. The excimer laser comprises a discharge cavity with two opposite exit ends, wherein a totally reflecting mirror is arranged at one exit end, while a prism and an optical grating are orderly arranged at the other exit end along a light path; the resonant cavity of the laser is composed of optical elements in the light path between the totally reflecting mirror and the optical grating; the output of the resonant cavity is located at the surface reflection position of the prism. Slits are formed in the two ends of the discharge cavity, respectively, and laser light out of the discharge cavity exits via the slits. The excimer laser comprises an etalon which is located in the output light path of the resonant cavity or the light path of the resonant cavity. The excimer laser is capable of realizing narrow-linewidth output of the excimer laser, and also capable of improving the energy and the stability of outputting laser light. Besides, the excimer laser is simple in structure, advantageous for cost reduction and convenient to tune.