Abstract: The energy of a series of output pulses of a solid state laser pumped by a diode array and triggered by a Q-switch is stabilized and rendered independent of the repetition rate by interrupting the pumping to allow the energy stored in the laser active element to fall at the commencement of an interval between a pair of Q-switch trigger signals that is longer than the interval corresponding to the chosen repetition rate. Before the second of this pair of Q-switch trigger signals occurs, the pumping is recommenced for a duration and at an input level that restore the stored energy to the value required for generating output pulses of the laser at the desired energy level.

Abstract: To maintain substantially constant the temperature of a diode junction of a pulsed, cooled, diode laser and hence the wavelength of the optical output of the laser, which laser is used for optically pumping a main, pulsed, solid state laser, the diode junction is heated by an external source during inactive intervals between pulses of the diode laser. This heating, which preferably is achieved by passing a heating current through the diode junction, is adjusted to ensure that, per a unit time greater than the length of an inactive interval, the heat energy received by the diode junction from this external heating together with the heat energy generated in the diode junction itself by the pulses is substantially constant independent of the length of the inactive intervals. Preferably the heating current has a constant level except for a period after each pulse when the level is reduced, e.g. to zero.