High brightness pumping of Yb-doped laser materials – Pampero

Few-cycle or single optical cycle pulse duration, carrier–envelope phase (CEP) control, high pulse energy are several signature requirements to laser sources dictated by modern high-intensity physics. The advent of the technique of chirped pulse amplification (CPA) 25 years ago and the invention of Ti:sapphire ensured a steady pulse intensity increase around the wavelength of 800 nm. However, the average power of the most advanced Ti:sapphire sources is limited to about 20 W, roughly defining the current state of the art as 1 TW peak power at a 1-kHz repetition rate. The goal of this project is to achieve a radical breakthrough in the average power and energy scalability of 5-100-kHz (multi)mJ femtosecond sources while ensuring wavelength tunability, CEP stability and the few-cycle pulse duration. Although Yb-doped materials are well suited for average power scaling because of the low parasitic heat excreted by the optical pump on the laser crystal, no broadband Yb amplifiers exist to date that could generate femtosecond pulses at the energy level higher than just a few mJ at a kHz repetition rate as a result of the low brightness of pump laser diodes and shortcomings of heat transport from the amplifier crystal. In this project, the 4 partners bring together their complementary proprietary knowhow that provides a perfect combination to resolve the multi tens kHz amplifier scalability challenge. The enabling pioneering concept contributed by CELIA to this project is a scalable fiber pump laser with an excellent beam quality and the concept of high-brightness pumping of long Yb materials with these fiber pump sources. The project will consists in the development of a high average power fiber pump laser around 976 nm, a controlled growth technique of long Yb-doped crystals and new laser architectures adapted to these crystals. The CIMAP laboratory is a expert in Yb-doped single crystal growth. The Laboratoire Charles Fabry de l’Institut d’Optique (LCF) works on diode pump femtosecond oscillators and amplifiers since many years. The startup compny Azur Light Systems will bring his industrial expertise to create an all fibered prototype pump laser. Finally, CELIA has become an expert in the design of innovative fibers (Rod type fibers and Bragg fibers) and develop since its beginning high energy femtosecond systems at high and ultrahigh repetition rates. CELIA has also pioneered the development of the high average power fiber lasers at 976 nm and naturally proposes the patented present concept of high brightness pumping of Yb materials . The mature Yb source will produce sub-200-fs pulses and reach the average power of 100 W, with a repetition rate ranging from 5 (20 mJ) to 100 KHz (1 mJ). This source can be used both as a direct high- intensity source for HHG attosecond pulse train generation as well as a pump source for a parametric amplifier generating few cycle pulses at 2 µm and further production of isolated attosecond pulses. Despite the high volume of technological innovation envisaged in this project, its emphasis lies on demonstrating the enabling nature of these laser source in table- top high-field applications that are in dire demand for higher statistics. The 10-100 KHz multi mJ level system should open unprecedented opportunities for coincidence momentum imaging and pump-probe experiments using XUV pulses and attosecond pulse trains.