30 W-average-power femtosecond NIR laser operating in a flexible GHz-burst-regime.

Laser sources which produce GHz bursts of ultrashort pulses attract a lot of attention by demonstrating superior performance in material processing. Flexibility of the laser source in a selection of parameters for custom application is highly preferable. In this work, we demonstrate a very versatile method for burst formation using the active fiber loop (AFL).

Active fiber loop for synthesizing GHz bursts of equidistant ultrashort pulses.

We demonstrate a method to synthesize ultra-high repetition rate bursts of ultrashort laser pulses containing any number of pulses within a burst with identical pulse separation and adjustable amplitude. The key element to synthesize the GHz bursts of ultrashort laser pulses is an active fiber loop. The method was implemented in the fiber chirped pulse amplification system to obtain 72 nJ-energy bursts of 20 pulses with a 2.