Cryo-cooled Yb:YAG Lasers for Advanced Photoinjectors

Advanced, high-brightness photoinjectors are required for the next generation of linear accelerators and free-electron lasers. Current photoinjector lasers are overly complex, due to the use of multiple amplifier stages to achieve the desired pulse energy, and have issues with power scaling. This project will develop a liquid-nitrogen-cooled, Yb:YAG, mode-locked-laser master-oscillator/power-­amplifier for use as a high-average-power laser source for laser photoinjector applications. A liquid-nitrogen-cooled, Yb:YAG master-oscillator/power-amplifier can provide average powers in excess of 100 W with repetition rates from 100 kHz to 1 MHz. The addition of a second amplifier stage can be used to generate 1 kW of average power in the form of 1 mJ pulses at a 1 MHz rate. In Phase I, the development of the cryogenic-Yb:YAG laser was initiated by building a prototype mode-locked laser, examining amplification techniques, and studying ways of temporally and spatially shaping the laser pulses. The prototype produced 55 W, 214 ps pulses at a repetition rate of 80 MHz. Phase II will involve the construction of a master-oscillator/power-amplifier that produces 1 to 3 mJ at 100 kHz repetition rates or 100 to 300 microjoule at a 1 MHz repetition rate. The wavelength will be approximately 1030 nm and the oscillator will be passively mode-locked to achieve pulse widths of approximately 10 ps. Commercial Applications and Other Benefits as described by the awardee: A relatively simple method of generating high-energy, picosecond pulses would fulfill an important near-term need as a source used in photoinjector applications for linear accelerators and free-electron lasers. Other applications of the basic technology would be in the areas of time-resolved spectroscopy, terahertz generation, and materials processing