PURPOSE: To excite more efficiently even in the case of vertical excitation system by placing a pin hole plate near a focal point converged by a convex when CVL light is generated between oscillators.

CONSTITUTION: A CVL oscillator 1 comprises a total reflecting mirror 5 and an output mirror 6 on both sides of a laser tube 4, Convex lenses 7a and 7b are laid out on an optical axis. When a pin hole plate 9 is placed near a focal point formed by the two convex lenses 7a and 7b, laser light 8a is oscillated and intensified, if the light is so focussed that it may pass through the pin hole plate. This construction makes it possible to enhance excitation efficiency in the case when optically excited laser, which uses CVL as its excitation optical source, is excited.