CC BY
17HiLASE-I-16
Unstable cavity lasers for compact short pulse high energy lasers
J. Hein1 J. Körner1, M.C. Kaluza1, D. Rostohar2, A. Lucianetti2, T. Mocek2, S. Zulic2 1Friedrich-Schiller University Jena, Institute of Optics and Quantum Electronics, Jena, Germany 2HiLASE Centre, Institute of Physics of the Czech Academy of Sciences, Dolni Brezany, Czech Republic
Nowadays, most diode pumped high energy class laser amplifiers follow the so called master oscillator power amplifier scheme. Here, an oscillator generates a rather low energetic pulse that is than further amplified stepwise by a chain of amplifiers. Though this concept is capable of delivering high energy pulses with very flexible pulse parameters, the complexity of such systems is a major drawback if it comes to robustness, size and economics.
We will present an alternative approach based on a novel unstable cavity design with intrinsic gain modulation that allows the generation of nanosecond pulses with more than 1 J output energy directly from a laser cavity with a top-hat shaped output beam distribution. The novel design reduces the minimum gain needed in such cavity compared to the state of the art unstable cavity layout using graded reflectivity mirrors and therefore can be combining this design with lower gain material like high efficient ytterbium doped gain media. Furthermore, our approach allows operating such cavity with zero output coupling, while still establishing a top-hat shaped intra cavity intensity distribution. Due to this the operation in a cavity dump mode or as regenerative amplifier is possible as well.
With a prototype system we demonstrated the operability of this design. The system is based on cryogenically cooled Yb:YAG ceramic and allows to generate an output energy of >1 J in a hexagonal top-hat beam. The system is very compact (approx. 80x60cm2) and also achieves a very high conversion efficiency of more than 30% from installed pump power to output energy.
