High power (100 W) Yb:YAG single-crystal fiber amplification chain for sub-ps MHz system(Orale)
Résumé
Since few years, the single-crystal fiber (SCF) technology has demonstrated very interesting features, combining the advantages of bulk crystals and glass fibers. Thanks to a very efficient thermal management and a high overlap between the guided pump and the unguided signal, SCF technology is well suited with the requirement of Master Oscillator Power Amplifier (MOPA) dedicated to high average power pulsed laser [1]. Recently, 30 W average power at 380 fs pulse duration has been demonstrated using a single SCF amplification stage [2]. In the frame of the European project " Ultrafast RAZipol " , we present in this paper a MOPA setup using three successive SCF amplification stages to reach an average power up to 100 W at sub-picosecond pulse duration and 20 MHz repetition rate. The seed laser is a passively-modelocked Yb-based laser delivering 356 fs / 20 MHz / 1,5 W / 1031 nm. The first stage consists of an Yb:YAG SCF (2% at., 1 mm diameter, 30 mm long) in a double-pass configuration pumped by a high brightness fiber-coupled laser diode (core diameter 100 µm, NA=0,22) emiting 120 W at 940 nm. The second amplifier is based on a simple pass through an Yb:YAG SCF (1% at., 1 mm diameter, 40 mm long) pumped by a wavelength stabilized 200 W fiber-coupled laser diode at 969 nm (core diameter 200 µm, NA=0,22) to reduce thermal load in the crystal. The output power reaches 65.5 W. The third stage uses an Yb:YAG SCF (1% at., 1 mm diameter, 30 mm long) in simple pass configuration pumped by a 120 W fiber-coupled laser diode at 940 nm (core diameter 100 µm, NA=0,22) to finally reach an average power of 100 W.