Micromachining hard materials for waveguides that can be coated and used at high pressures for HHG (Title on abstract and summary is "Micromachined Hardened Waveguides for High Harmonic Generation (HHG)")

Statement of the problem or situation that is being addressed: In this project, we propose to develop waveguides specific to high harmonic generation, that are more efficient than standard HHG waveguides, can handle pressures in excess of > 30 bar, minimize losses for wavelengths > 1 m, and can be manufactured with ultrafast micromachining. Current waveguides using hollow core fused silica are a great way to engineer the output from ultrafast HHG. However, the transmission of these waveguides depends heavily on Fresnel reflections at the interior surface. This leads to a decrease in transmission which goes as the cube of the diameter, and longer wavelengths will experience massive losses. In addition, at pressures much higher than 30 bar (required for phase matching at longer wavelengths) fused silica may not have the required tensile strength, which can lead to fiber detonation. This impacts laser seed sources for the next generation seeded XFELs (X-Ray Free Electron Laser). Statement of how this Problem or Situation is being addressed: Our approach is to use femtosecond micromachining to cut waveguide structures into harder materials such as metals, sapphire, and diamond for an increase in transmission (this method allows easy interior coatings for the drive laser), safety, and thermal handling. It will also simplify the method of injecting the high pressure gas for the X-Ray generation, and allow differential pumping schemes to avoid absorption of the resultant X-Ray laser beam output. Commercial Applications and Other Benefits: The applications are, specifically, enhancements to high repetition rate X-Ray lasers, Waveguide laser accelerators, semiconductor fab, and seeding of XFEL light sources. Scientific applications would include new table top sources for medical imaging, spectroscopy, and biochemistry. Key Words: X-Ray, Ultrafast, High harmonic Generation, EUV, Laser Summary for Members of Congress: We propose to develop technology critical to next generation table top X-Ray laser sources, which can be used in next generation light sources. These laser systems have applicability in medical imaging, semiconductor fab metrology, and research tools for universities and national laboratories. This work would enhance the capabilities of currently operating light sources, and would allow studies of chemical and biological systems on the molecular level, and would be capable of producing extremely short pulses at X-Ray wavelengths useful for time-resolved spectroscopy and imaging on the nanoscale.