Patent ID: 8378255

Claim:
A laser beam irradiation apparatus comprising: laser beam generation means for emitting a laser beam, an optical fiber for transmitting the laser beam incident on an input side face thereof to an output side face thereof, an incident optical unit for making incident the laser beam emitted from the laser beam generation means on the input side face of the optical fiber, and an emission optical unit for applying the laser beam emitted from the output side face of the optical fiber to an irradiation portion, wherein the laser beam generation means includes a vertical multimode laser oscillator generating, the laser beam, a width of a wavelength of the laser beam being 1 nm or greater, and a cross section of a core of the optical fiber is rectangular for 5 m to 10 m from an output side face of the core, and each side of the rectangular cross section has a length 25 times as long as or longer than the wavelength of the laser beam.