LASER DEVICE

PURPOSE:To prevent the base section of an exit total-reflection mirror of an unstable resonator from being irradiated with diffracted light from the opening of the mirror by providing a taper on the side face of the opening of the exit total-reflection mirror. CONSTITUTION:An exit total-reflection mirror 22 is provided with a laser light taking-out opening 222 formed by linearly notching part of the mirror 22. The side face 225 of the opening 222 is formed by forming a tapered section at the notched section at an angle of phi against an optical axis (a). In addition, mirrors 12 and 22 are arranged so that they can become confocal. Almost all of the rays of light advancing toward the opening from the inside of a resonator are parallel rays against the optical axis, but, when the rays of light pass through the opening 222, they are diffracted by the mirror surface-side edge section 223 of the mirror 22 and become laser light 8 which is spread in the optical-axis direction by an angle theta from the optical axis. The diffracted light is discharged to the outside from the resonator without irradiating the base section of the mirror 22. In addition, no heat is generated from the side face section 225 of the mirror 222.