Laser device and optical amplifier

A laser device, comprising:

• a resonator;
• a plurality of solid gain media, having fluorescent spectra that at least partially overlap with each other, provided within the resonator;
• and
• pumping means, for pumping the plurality of solid gain media;
• wherein:
• the entire fluorescent spectrum width of the plurality of solid gain media is greater than the fluorescent spectrum width of each solid gain medium, employed as a variable wavelength laser device;
• the pumping means causes at least one laser beam to enter the plurality of solid gain media as at least one pumping light beam, to pump the plurality of solid gain media, and
• the plurality of solid gain media are arranged in order from the direction in which the pumping light beam enters;
• and
• the variable wavelength laser device includes a wavelength modulating element, wherein:
• the plurality of solid gain medium include Lu3Ga5O12;
• Gd3Sc2Al3O12 and Gd3Sc2Ga3O12 in this order from the direction in which the laser beam enters, each gain medium having fluorescent spectrum bandwidths of less than 1.6 nm, respectively, and the entire spectrum width becomes approximately 3 nm.