A calorimeter is an object used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Laser calorimeters are devices used for measuring the laser pulse energy by measuring the increase in temperature of an optical absorber irradiated by a laser beam. Laser calorimeter development has been driven by the needs of its users, such as wavelengths of operation, beam size, and energy level to be measured. These devices are used for applications such as measuring multi-millisecond pulses or average power of laser pulses over various periods of time.