Date of Award
Doctor of Philosophy (PhD)
Coherent keV photon energy x-rays have many applications for materials science at the shortest length and time scales. Unfortunately, there are relatively few options for coherent x-ray generation. One of the most promising methods is high harmonic generation, wherein a femtosecond driving laser pulse is coherently upconverted to the x-ray region of the spectrum. Recent work has shown that the maximum x-ray photon energy that can be generated via high harmonic generation scales favorably with the wavelength of the driving laser pulse. This has sparked an interest in using mid-infrared (3-5_m) lasers to drive high harmonic generation.
However, high harmonic generation necessitates a mJ level, kHz repetition rate, femtosecond driving laser. At present, there are no such lasers in the mid-infrared region of the spectrum. This necessitates the development of new laser architectures for tabletop coherent x-ray generation.
OPCPA technology is one of the most promising avenues for high energy, high repletion rate lasers in the mid-infrared. This thesis reports on the design and development of a mJ level, kHz repetition rate, femtosecond OPCPA laser running at 3μm, optimized for tabletop coherent x-ray generation.
The system described here integrates and extends a variety of laser technologies towards this goal. The full laser is based upon an Yb:_ber oscillator and MgO:PPLN OPO front end. To pump our OPCPA system, we developed a four stage, cryogenic Yb:YAG laser running with >35mJ of output energy at 1kHz. We then use this to a pump a three stage OPCPA system, likewise running at 1kHz. We demonstrate over 3.4mJ of output energy at 1.55_m, along with 1.4mJ at 3μm. We then show compression of the 3μm output to <110fs. Finally, we conclude with the future directions for this laser, and discuss how it may be scaled to higher energies, shorter pulse lengths, and even further into the mid-infrared.
Gerrity, Michael R., "Development of a High Energy, kHz, Mid-Infrared OPCPA Laser for keV High Harmonic Generation" (2015). Physics Graduate Theses & Dissertations. 131.