Processing method and processing apparatus using interfered laser beams
Provided are a processing method and a processing apparatus which are capable of suppressing a disturbance attributable to a surface wave in a processing by interfered laser beams, in particular, a processing by the interfered laser beams of a pulsed laser having a pulse width of equal to or more than 1 fs and of equal to or less than 1 ps, in which the wavelength of a surface wave that propagates in a direction of the interference of the laser is made longer than a pitch of the interference of the laser on a surface of an object to be processed to process the object.
1. A processing apparatus having a pulsed laser of which a laser beam is divided into plural laser beams which are caused to interfere with each other at a processing portion of a surface of an object, the processing apparatus comprising:
an oscillator for oscillating the laser beam;
a beam splitter for dividing the laser beam into divided laser beams;
an optical path length adjuster for changing an optical path of the divided laser beams; and
a wavelength plate located in the optical path of each of the divided laser beams and rotated to an angle where a polarization direction of the divided laser beams is made p-polarized,
wherein the processing portion is located at a position where the divided laser beams, in which the polarization direction has been made p-polarized, are overlapped.
2. The processing apparatus according to claim 1 , wherein the laser beam oscillated by the oscillator comprises a pulsed laser beam having a pulse width of equal to or more than 1 fs and of equal to or less than 1 ps.