Ultraviolet laser apparatus

An ultraviolet laser apparatus, comprising:

• a semiconductor laser that emits an excitation laser light;
• a fiber laser medium to which the excitation laser light enters from the semiconductor laser and that causes laser oscillation;
• and
• an external resonator that converts a wavelength of a laser light oscillated in the fiber laser medium, wherein
• the external resonator comprises:
• one nonlinear optical crystal that has a higher harmonic wave generating function for converting the wavelength and also functions as a phase conjugate mirror;
• a plurality of high reflectivity mirrors;
• and
• a feedback mechanism that controls a phase of the laser light,
• once the laser light enters the external resonator, the phase conjugate mirror reflects the laser light and the reflected light travels along a reverse optical path to reach an end face of the fiber laser medium, the excitation laser light entering the end face and the laser light being reflected on the end face, such that the fiber laser medium and the phase conjugate mirror cause the laser oscillation and the nonlinear optical crystal generates a higher harmonic wave of the laser light by the laser oscillation, and
• the external resonator outputs an ultraviolet region continuous wave of at least 0.1 W.