Date of Award

Spring 1-1-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics

First Advisor

Margaret Murnane

Second Advisor

Henry Kapteyn

Third Advisor

Sterling Backus

Fourth Advisor

Thomas Schibli

Fifth Advisor

David Jonas

Abstract

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.

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Optics Commons

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