Evolution is a family of diode-pumped, intra-cavity doubled, Q-switched Nd:YLF lasers designed for pumping Ti:Sapphire amplifiers, such as the Coherent Legend Elite, Legend Elite Duo, or Libra, and for materials processing. The Evolution model number (-15, -30) is determined by the average power output when the laser is running at 5 kHz. The Evolution-HE is a high energy model, optimized to give >45mJ per pulse at 1kHz. Also available for the Evolution family is the Double Pulse Option (DPO) that is designed for particle imaging velocimetry (PIV) and high-speed imaging. The DPO option comprises an additional electronic control box with software interface (GUI) that fires the Evolution Q-switch twice in rapid succession to provide a pair of closely spaced output pulses at the nominal repetition rate of the laser. The time between these two pulses is user-adjustable from 1 to 150 microseconds..