Laser device, multi-wavelength laser device, and photoacoustic measurement apparatus

A multi-wavelength laser device, comprising:

• a first laser unit that oscillates first laser light at a first wavelength;
• a second laser unit that oscillates second laser light at a second wavelength that is a wavelength longer than the first wavelength;
• and
• a wave-combining unit that causes an optical path of the first laser light output from the first laser unit and an optical path of the second laser light output from the second laser unit to coincide with each other, wherein:
• the second laser unit is laser device comprising:
• a laser crystal;
• a resonator including a pair of mirrors between which the laser crystal is interposed;
• a Q switch that is disposed on an optical path of the resonator and controls a Q value of the resonator;
• and
• a Brewster thin-film polarizer that is disposed on the optical path of the resonator and transmits selectively p-polarized light,
• wherein the thin-film polarizer has wavelength selectivity in which a p-polarized light transmittance at a first wavelength exhibiting a maximum gain of the laser crystal is 5% or more to 25% or less, the p-polarized light transmittance monotonically increases as a wavelength becomes longer than the first wavelength, and a maximum transmittance is exhibited at a third wavelength, and
• wherein the laser device oscillates laser light at a second wavelength that is a wavelength longer than the first wavelength and shorter than or equal to the third wavelength and that has a p-polarized light transmittance of 90% or more in the thin-film polarizer, and
• the first laser unit is a laser device that has the same configuration as the second laser unit and that comprises a non-coated Brewster polarizer instead of the Brewster thin-film polarizer.