The TETRA laser from AMS Technologies is a rapidly tunable DPSS lasers that emits very short laser pulses (< 5 ns) of high energy (up to 20 µJ) at four wavelengths in the visible range - 532 nm, 555 nm, 579 nm, 606 nm. These lasers are particularly suitable for multispectral photoacoustic imaging. Using sophisticated technology, the TETRA laser can switch from pulse to pulse between these four wavelengths with a very high pulse repetition frequency of 2 kHz. The laser has an RS232 interface which can be used to switch the laser on/off, set laser energy, set wavelengths of sweep mode, enable/disable emission. TETRA consists of two separate units - one box contains the electronics for the entire power supply as well as the pump laser diode. The optical output of this laser diode is coupled via an optical fiber to the second box, which contains the actual laser head. Due to this design, the heat dissipated by the power supply circuit and the pump laser diode remains within the power supply unit, and the laser head benefits from reduced thermal loading.