Laser device and photoacoustic measurement device

A laser device comprising:

• a laser rod which includes alexandrite crystal;
• an excitation light source which irradiates the laser rod with excitation light;
• a resonator which includes a pair of mirrors with the laser rod sandwiched therebetween;
• a Q switch which is inserted into the optical path of the resonator and controls the Q value of the resonator;
• and
• a Brewster polarizer which is inserted at least between the laser rod and the Q switch or between the laser rod and one of the pair of mirrors, selectively transmits light in a predetermined polarization direction among light emitted from the laser rod, and has a film for separating light in the predetermined polarization direction from light in a polarization direction orthogonal to the predetermined polarization direction,
• wherein the Q switch includes a Pockets cell, in a case in which an applied voltage to the Pockels cell is a first voltage, the Q value of the resonator is higher than a laser oscillation threshold, and in a case in which the applied voltage is a second voltage higher than the first voltage, the Q value of the resonator is equal to or less than the laser oscillation threshold, and
• wherein, in a case in which an input energy to the excitation light source is 20 J, the range of an applied voltage to the Q switch for making the Q value of the resonator equal to or less than the laser oscillation threshold is equal to or greater than 2.5 kV.