Laser processing apparatus

A laser processing apparatus comprising:

• a chuck table configured to hold a workpiece;
• and
• laser beam irradiating means for irradiating the workpiece held on the chuck table with a pulsed laser beam;
• the laser beam irradiating means including
• a laser oscillator in which a repetition frequency is set so as to oscillate a pulsed laser having a pulse width shorter than a time of electronic excitation caused by irradiating the workpiece with a pulsed laser beam and oscillate at least two pulsed laser beams within the electronic excitation time, wherein the at least two pulsed laser beams are temporally spaced from each other,
• a condenser that irradiates the workpiece held on the chuck table with the at least two pulsed laser beams oscillated by the laser oscillator,
• thinning-out means for guiding the pulsed laser beams necessary for processing to the condenser while simultaneously thinning out and discarding pulsed laser beams in a predetermined cycle, the thinning-out means being disposed between the laser oscillator and the condenser, the thinning out means including an acoustooptic element and a damper, said acoustooptic element being in direct communication with said damper, wherein said acoustoooptic element changes an optical path of the pulsed laser beams to guide the pulsed laser beams to said damper and the pulsed laser beams necessary for processing to the condenser, wherein the thinning-out means thins out the pulsed laser beams such that a time from application of a first pulsed laser beam of said at least two pulsed laser beams to application of a second pulsed laser beam of said at least two subsequent pulsed laser beams is equal to or more than a time taken for heat generated in the workpiece to be released after the application of the at least two previous pulsed laser beams, and
• an amplifier disposed between the thinning-out means and the condenser, said amplifier configured to increase output power of the at least two pulsed laser beams necessary for processing that are outputted from the thinning out means and directed to the condenser.