Interference coatings for high energy and average power femtosecond-class lasers in the 0.8-2?m wavelength range

The problem/situation that is being addressed concerns the development of near infrared ultrafast interference coatings(IC) for high average power femtosecond lasers that will meet the specifications of the DoE solicitation: “broad-bandwidth, laser damage threshold of 0.5 J/cm2 (1 ps), engineered using a process that is scalable to large areas.” Advances in compact high gradient laser-driven plasma accelerators depend on the availability of efficient femtosecond lasers capable of delivering multi-Joule pulses at kHz repetition rates.The development of ultrafast interference coatings (ICs) with superior laser damage is strongly motivated by the intensive efforts worldwide towards demonstrating compact high gradient laser-driven plasma accelerators.Scaling the average power of femtosecond lasers to meet the requirements of future plasma accelerators demands superior performance from ICs, which tend to fail at relatively low fluence.XUV Lasers Inc. in collaboration with the Ohio State University (OSU), University of New Mexico (UNM) and Colorado State University (CSU), proposes a combined modeling and experimental effort to develop ultrafast ICs for femtosecond class lasers operating in the 0.8-2 µm wavelength range. There are unique aspects to our effort. The UNM and OSU teams have developed comprehensive models of laser/matter interactions and femtosecond laser damage of thin films. The CSU team has the capability to grow high quality ICs by ion beam sputtering. OSU and XUV Lasers can test laser damage performance over a broad range of wavelengths (0.26 to 4.2 mm) and pulse widths from a few femtosecond to picoseconds. In Phase I, the models will be used to predict laser damage performance of IC for 0.8 and 1.03 mm wavelengths and for pulse durations of 10 fs, 100 fs and 5 ps. The model predictions will guide IC design and fabrication. The results of laser damage tests will enable benchmarking and refining of the models. The output of this iterative process will be ICs of superior laser damage performance. The results of Phase I will enable us to formulate a cohesive plan for Phase II focused on modeling and experiment of ultrafast, ultra-broad band ICs for laser wavelengths up to 2 mm and pulse duration down to a few femtoseconds.ICs are a proven established technology for comparatively low fluence, narrow bandwidth near infrared lasers.However, ICs fail dramatically when tested with ultrashort pulses. This challenge coupled with a scarce market for ultrabroad bandwidth, ultrafast coatings open up enticing commercial opportunities. Ultrafast ICs with superior laser damage performance will advance the engineering of high average power femtosecond lasers pursued as drivers for future colliders. Considering the growing investments in compact laser-based accelerators worldwide, efforts as proposed will ensure the United States remain competitive in critical IC technology.