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Millijoule Level Laser System Delivering 1 to 18 Ghz Intra-Train Repetition Rate Picosecond Pulses for Materials Processing

Ultrafast laser systems are very popular for material processing applications. Commonly, these systems operate at repetition rates ranging from kHz to MHz regime. However, recent works [1] have demonstrated the potential of processing materials with bursts of GHz pulses and reported higher efficiencies. Despite these encouraging first demonstration, many aspects have still to be investigated. In our project, we aim to determine the best GHz laser regime to achieve higher efficiency and higher quality during material processing in the burst mode. Such an in-depth study is being carried out thanks to a versatile laser system developed in our lab [2]. In this contribution we will present our GHz pulse repetition rate (PRR) laser system continuously tunable from 1 to 18 GHz and able to operate in burst mode. The pulse duration at the output is compressed down to 1 ps. Additionally, the number of pulses per burst, i.e. the burst length is adjustable from a few to several thousands. Moreover, the shape of the envelop of each single burst can also be chosen and set to an arbitrary form (flat, ramped on or off …). Finally, the burst repetition rate (BRR) can be set from 20 kHz up to several tens of MHz. The average power reached up to 20 W which correspond to a maximum energy of about 1 mJ per burst at 20 kHz.