Laser apparatus and laser machining apparatus

A laser apparatus comprising:

• a laser oscillator where mode hopping occurs;
• an acousto-optic modulator including a first acousto-optic modulator to diffract a laser beam from the laser oscillator when a first ultrasonic wave is applied and a second acousto-optic modulator to diffract a higher order beam output from the first acousto-optic modulator when a second ultrasonic wave is applied, a propagation direction of the first ultrasonic wave relative to a diffracted direction of a higher order beam emitted from the first acousto-optic modulator and a propagation direction of the second ultrasonic wave relative to a diffracted direction of a higher order beam emitted from the second acousto-optic modulator being different in causing a frequency shift that is caused by the first acousto-optic modulator and a frequency shift that is caused by the second acousto-optic modulator to cancel each other out;
• an amplifier to amplify a laser beam from the acousto-optic modulator;
• and
• an expander to expand a beam diameter of the laser beam, the expander being disposed on an optical path between the acousto-optic modulator and the amplifier.