| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that, as a dispersion compensation medium which is used inside a resonator of an ultra-short pulse laser, a GT interferometer mirror is created by electron beam evaporation of relatively low cost and has an advantage in being priced lower than a chirp mirror which is created using ion beam sputtering but in a wavelength band of 80 nm where predetermined negative group delay dispersion is given, the wavelength band is insufficient to generate an ultra-short pulse having a pulse width of about 30 fs or less and in order to perform oscillation with a shorter pulse width, it is required to further widen the bandwidth having a negative value of group delay dispersion.SOLUTION: The dispersion compensation medium uses a first GT interferometer mirror in which the thickness of a low refractive index layer of a second layer from the top face is 2l, and a second GT interferometer mirror in which the thickness of a low refractive index layer of a second layer from the top face is 4l, while pairing the first and second GT interferometer mirrors in such a manner that a negative peak position of group delay dispersion of the second GT interferometer mirror overlaps a positive peak position of group delay dispersion that the first GT interferometer mirror has. Therefore, a wavelength bandwidth of group delay dispersion having a required negative value is widened. |
