Along with the improvement of laser beam performance (particularly, improvements in the technology for increasing the output of laser beams and the technology for shortening the wavelengths of laser beams), laser processing technology using lasers (e.g., using a laser as a light source for lithography in LSI manufacturing) has grown to be one of industries' core technologies. In addition to increasing the output of laser beams and improving the efficiency of laser beams, shortening of the wavelengths of laser beams is desired for implementing finer and more precise processing.
In recent years, nonlinear optical technology using high intensity attosecond light sources is developing (see, for example, Non-Patent Documents 1 and 2). Such optical technology is targeted for a soft X-ray wavelength range.