Development of New Mid-Infrared Ultrafast Laser Sources for Compact Coherent X-ray Sources

Bright coherent light sources in the soft x-ray region of the spectrum are useful for a variety of applications of interest to the DOE. However for many applications, such as nanometer-scale microscopy in the ¿water window¿ region of the soft x-ray spectrum (300-500 eV), only large-scale synchrotron facilities are currently capable of generating the required flux. Yet, the implementation of small-scale, tabletop sources of bright coherent soft x-rays would greatly expand the potential impact of the technologies developed at synchrotrons, allowing the source to be brought to applications in science and industry. One promising approach to addressing this need involves the coherent upconversion of laser light to short wavelengths through the process of high-order harmonic generation. The basic physics of the high-order harmonic generation process makes it easier to generate and phase-match shorter-wavelength harmonics when the process is driven by longer wavelength light. This project will develop an ultrafast laser amplifier that operates at wavelengths ~3x longer than current generation ultrafast lasers. This mid-infrared ultrafast laser will be integrated with a new set-up for high-order harmonic generation. In Phase I, the temperature dependence of the absorption and emission spectra was measured for two gain materials, which could serve as the driving source for generating soft x-ray light through the high-order harmonic generation process. The most promising gain material was selected, and a two-stage multipass amplifier system was designed. In Phase II, the design will be implemented in the construction of the mid-infrared laser amplifier system, and the amplified pulses will be used to generate efficient high-order harmonic light at 13nm and 4nm, with sufficient flux for applications. Commercial Applications and Other Benefits as described by the awardee: The development of these lasers should directly translate into brighter tabletop soft x-ray sources for applications in control, diagnostics, and metrology. Currently, a $7B global laser market exists for ultraviolet, visible, and infrared laser systems.