Patent Number: 
Section: abstract

A laser irradiation apparatus is provided in which the occurrence of adverse effects on an object to be irradiated with a laser beam due to the difference in the polarization state between pulsed laser beams can be prevented or significantly reduced when the pulsed laser beams emitted from two laser light sources are guided to pass through the same optical path for irradiation of an object to be irradiated with the pulsed laser beams. The laser irradiation apparatus is provided with a first laser light source 3, a second laser light source 4, an optical path combining optical member 7 which guides the pulsed laser beams emitted from the first laser light source 3 and the second laser light source 4 to pass through the same optical path, and a polarization control member 9 which controls polarization state of the pulsed laser beam from the optical path combining optical member 7. The polarization control member 9 includes a first polarization control portion 13 and a second polarization control portion 15 through which beam components of the pulsed laser beam pass. The polarization states of the beam components that have passed through the first polarization control portion 13 and the beam components that have passed through the second polarization control portion 15 become different from each other. The beam components in different polarization states are superimposed on each other on a surface to be irradiated with the laser beam of the object to be irradiated with the laser beam.