OP: Transforming Table-top Soft X-Ray Lasers into High Average Power Devices

Colorado State University, Fort Collins CO

Investigators

Abstract

Transforming Table-top Soft X-Ray Lasers into High Average Power Devices Abstract Non-Technical: Recent advances in compact and more readily accessible "table-top" soft x-ray lasers based on plasma amplifiers are enabling nano-scale applications including ultra-high spatial resolution microscopy, the defect-free printing of nanostructures, the study of the electronic structure and reactivity of nano-clusters and molecules, and the development of chemically sensitive nano-probes that will be able to map the composition of nano-scale objects in 3-dimensions. While these lasers have the advantage of their compact size, their use in many applications is still limited by their low average power. The proposed research is designed to advance table-top soft x-ray lasers into high average power devices , with the goal of ultimately achieving multi-milliwatt average power laser beams in the 60-100 eV photon energy region from a compact device, greatly impacting applications in several fields. We plan to achieve a significant increase in average powers by tailoring the plasma amplifier with an unprecedented level of control to achieve higher efficiency while simultaneously increasing the repetition rate by using a new type of diode-pumped high energy ultra-short pulse laser driver. Technical: In the present state-of-the-art collisional soft x-ray lasers only several percent of the laser pump energy is deposited in the gain region. Recent experiments and simulations show that relatively minor alterations in the pump energy temporal distribution can result in a large increase in the soft x-ray laser efficiency. We propose to take advantage of this unexploited high sensitivity to significantly increase the efficiency and output power by tailoring the pump energy deposition rate with a high level of control to create a plasma with larger gain and reduced refraction loses. Extensive sets of hydrodynamic/atomic physics simulations and experiments covering a broad range of pump parameters will be conducted to identify the pump pulse sequence that maximizes the soft x-ray laser output energy. The resulting increase in the soft x-ray laser efficiency will be combined with an increase in repetition rate made possible by a novel high energy diode-pumped solid state laser driver. This could result in table-top soft x-ray laser beams with orders of magnitude higher average output powers in the 60-100 eV photon energy region than presently available compact coherent sources. The more efficient pumping will also facilitate the extension of practical soft x-ray lasers to shorter wavelengths. The transformation of compact soft x-ray lasers into high average power devices can be expected have a broad technology impact in nanoscale imaging, defect-free patterning of materials, and materials characterization. The propose research will provide exciting multi-disciplinary thesis projects for graduate students, with the opportunity of working in both the engineering and the physics of advanced laser systems. The proposed project will also contribute to train a diverse workforce of an area of great industrial interest and economic impact, as the semiconductor industry is approaching the start of the mass production of computer processors using extreme ultraviolet lithography. We plan to use the opportunities offered by the proposed project to involve a diverse group of undergraduates, high school students, and high school teachers in research. We plan to include the participation of high school students in the project during the summers.