SBIR-STTR Award

In this project, we seek to advance high intensity laser technologies of interest to laser plasma acceleration (LPA) of electrons, as well as for applications of laser-accelerated electrons for light source applications including Inverse Compton Scattering gamma sources and betatron x-ray sources. Past experience in laser science has proven that progress in understanding and optimizing any application is greatly accelerated when the process can be implemented with high repetition- rate kHz lasers: this not-only increases the average power and data acquisition rate, but also allows data acquisition at frequencies well above the “1/f noise” spectrum typical of experimental applications, allowing for faster optimization. Furthermore, the more-interactive nature of experimentation facilitates the discovery of new regions of parameter space and new phenomena. To-date, few experiments have made use of kHz lasers for laser plasma acceleration, because of the very high peak power requirement to accelerate electrons to relativistic energies of ~25-100 MeV, while maintaining the narrow energy spread necessary for the majority of applications. However, several recent developments have made such a prospect both interesting and feasible. Several groups have used very short-duration, sub-TW pulses to accelerate electrons to few-MeV energy with broad spectral bandwidth—proving that LPA at kHz repetition rates is possible. Also, several experiments done with lower rep-rate lasers have demonstrated that low energy spread electron beams in the range of 30-100 MeV can be generated using pulses of few-TW peak power. The development of a kHz repetition-rate, multi-TW laser will make it possible to access this parameter range—and is a feasible prospect. In the past, KMLabs has delivered ~ 1 TW/ 1 kHz lasers to customers; but to-date the laser technology has not as-yet reached any known physical limit. In this project, we plan to explore in Phase I, and implement in Phase II, the first, to our knowledge, multi-TW kHz repetition-rate laser. Our goal will be to demonstrate near-diffraction- limited focusability, a 15-20 fs pulse duration, a peak focused intensity consistent with all laser parameters, and a laser that can relaibly operate 24/7 without drift in parameters. This performance is possible using advanced pulse shaping and beam characterization methods, as well as optimized cryogenic cooling in Ti:sapphire amplifiers. To keep within the budget parameters of Phase II, we will make use of existing equipment at KMLabs—with the goal of implementing a sub-scale demonstration, and then collaborating with Lawrence Berkeley National Laboratory to implement the full system (100 mJ, 1 kHz,

In this project, we seek to advance highintensity laser technology relevant to laser plasma acceleration, other highenergy physics applications, and applications in lightsource technology relevant to DOE. KMLabs has specialized in the development of high average power laser systems with pulse duration in the fewoptical cycle regime, near the fundamental limits of pulse duration. However, LPA requires high peakpower laser pulses—lasers that have in the past only operated at very low pulse repetition rates. Our goal is to develop a kHz repetitionrate laser with unprecedented high peak power. We plan to build a single tabletop laser with 510 TW peak power, operating at 1 kHz repetitionrate, and capable of accelerating electrons to relativistic energies of ~25100 MeV. This project will thus provide an unprecedented platform for implementing laserplasma acceleration on a relatively small scale, and with a laser that operates stably at repetition rates that allow for precision studies of the LPA process. It also ideal for applications, for example for studies of dynamics in radiation chemistry. In phase I of this project, we investigated the thermal management and optical considerations necessary to produce multiTW pulses with our kHz ultrafast lasers. We identified parameters within the laser amplifier crystal and thermal management that, upon optimization, will allow higher pump powers and thus higherenergy amplified pulses. We directly measured the thermal conductivity of several key materials at the cryogenic temperatures used in these high average power lasers, but where there was no preexisting data in the literature. These findings provide guidance for building a laser amplifier capable of generating ultrafast pulses with 100200 mJ energy and 100200W average power—a new milestone in ultrafast laser performance. Importantly, we will achieve this performance while maintaining the exceptional beam quality necessary for LPA and other highfield applications such as high harmonic generation. In subsequent phases, we will add a booster to the amplifier, following closely the Phase II design principles to substantially increase the output power achievable in a tabletopscale laser system. Our goal is 100150 mJ pulse energy, with >5 TW peak power in 15 20 femtosecond pulses, and >100W average power. This work will notonly provide an unprecedented technology demonstration key to many DOE goals including LPA, but will also also bolster the technical specifications of all our commercial laser systems. For example, our XUUS EUV will produce much higher photon fluxes when pumped by a more powerful amplifier. This will make the product attractive to markets such as semiconductor lithography and metrology, that require brighter and shorterwavelength light sources. Thus, advances made possible by this SBIR will dramatically strengthen our ability to serve these and other important markets.