100 fs LED-pumped Cr:LiSAF regenerative amplifier

Transition metal-doped gain media such as Ti:sapphire, Cr:LiSAF and Alexandrite are the most appropriated crystals for femtosecond laser chains with pulse duration below 100 fs. However, because of a low gain and an absorption band in the green/red region, these materials are difficult to pump directly with diodes. Hence, the main issue for a femtosecond laser chain is the complexity and the high cost of the pump sources for the amplifiers. One innovative solution is to take advantage of the compactness, robustness, and low price of the light-emitting diodes (LED) to pump transition metal-doped gain media. In this work, we report, to our best knowledge, the first femtosecond amplifier pumped by LED. For this demonstration, we choose the Cr:LiSAF crystal for its combination of high absorption, large emission cross section and relatively long radiative lifetime. We then present a LED-pumped Cr:LiSAF regenerative amplifier in a femtosecond laser chain.