Laser machining apparatus

A laser machining apparatus comprising:

• chuck table operable to hold a workpiece;
• and
• laser beam irradiation means operable to irradiate the workpiece held by the chuck table with a laser beam,
• the laser beam irradiation means including
• a pulsed laser oscillator adapted to oscillate a pulsed laser beam at a given repetition frequency,
• first and second condensers adapted to collect the pulsed laser beam oscillated by the pulsed laser oscillator, and
• beam splitting means arranged between the pulsed laser oscillator and the first and second condensers to split the pulsed laser beam oscillated by the pulsed laser oscillator and direct the resultant beams alternately toward the first and second condensers,
• the beam splitting means including a photoelastic modulator that has a piezo element and synthetic quartz formed in one piece and modulates the laser beam so that a polarization plane of the laser beam is alternately at 0 and 90 degrees by applying, to the piezo element, a high frequency voltage at a frequency that matches the natural frequency of the synthetic quartz.