Patent Number: 
Section: claims

1. A laser irradiation apparatus comprising:a first laser light source configured to emit a first polarized pulse laser beam;a second laser light source configured to emit a second polarized pulse laser beam which is different from the first polarized pulse laser beam;an optical path combining member configured to guide the first polarized pulse laser beam and the second polarized pulse laser beam to pass through a same optical path;a polarization control member arranged in a direction perpendicular to a traveling direction of laser beams, wherein the polarization control member includes a first polarization control portion and a second polarization control portion, each of which controls a polarization state of beam components of the pulsed laser beam from the optical path combining member, wherein the polarization state controlled by the first polarization control portion is different from that controlled by the second polarization control portion; anda laser beam superimposing member configured to superimpose the pulsed laser beam which has passed through the first polarization control portion and the pulsed laser beam which has passed through the second polarization control portion with each other on a surface to be irradiated of an object,wherein the first laser light source and the second laser light source emit linearly-polarized pulse laser beams of which polarization directions are at 90° to each other,wherein the first polarization control portion and the second polarization control portion are quarter wave plates which each have an optical axis at an angle of 45° with respect to each of the polarization directions of the pulsed laser beams emitted from the first laser light source and the second laser light source, andwherein the optical axes of the first polarization control portion and the second polarization control portion are at 90° to each other. 2. The laser irradiation apparatus according to claim 1, further comprising a pulse control device which controls the first laser light source and the second laser light source so as not to synchronize timing of emission of the pulsed laser beams from the first laser light source and the second laser light source. 3. The laser irradiation apparatus according to claim 1, further comprising a beam expander which adjusts a shape of the pulsed laser beam from the optical path combining member so that the pulsed laser beam from the optical path combining member has an elongated shape and which sends the pulsed laser beam having an elongated shape to the polarization control member. 4. The laser irradiation apparatus according to claim 1,wherein the length of the first polarization control portion in an arrangement direction and the length of the second polarization control portion in an arrangement direction are set so that a total amount of energy of beam components of the pulsed laser beam which have passed through the first polarization control portion is substantially equal to a total amount of beam components of the pulsed laser beam which have passed through the second polarization control portion. 5. The laser irradiation apparatus according to claim 1,wherein at least one of the first polarization control portion and the second polarization control portion is divided into plural parts so as to sandwich all or a part of the other of the first polarization control portion and the second polarization control portion in an arrangement direction. 6. The laser irradiation apparatus according to claim 1,wherein an optical path length of the pulsed laser beam inside the second polarization control portion is substantially equal to an optical path length of the pulsed laser beam inside the first polarization control portion.