HAPPIE Results

The HAPPIE Joint Research Activity built on high power/high rep rate European project investments. It targeted new technological developments centred on a high power mission, and was aligned to a vision of future high average, high peak power developments with: DPSSL lasers designed and used to provide high average but low peak power. High peak power being achieved by efficiently converting the low peak power output of the DPSSL laser chains into a high peak power through a non-linear interaction – OpticalParametric Chirped Pulse Amplification (OPCPA). Single beam systems of (1) and (2) being finally coherently combined to further increase power.

MBI (left) and LULI (right) DPSSL laser heads

The activities of objective 1 (DPSSL) were dedicated to face pumped thin disc technology and photonic rod fibres. Within
this framework:

• MBI developed a multipass amplifier with 17 mm disc diameter delivering more than 550 mJ at a 100 Hz repetition rate.
• FSU concentrated its efforts on cryogenic studies with an efficient (>45%) CaF2 laser source delivering more than600 mJ.
• IST developed a Yb-based diode-pumped amplifier delivering 80 mJ at 0.5 Hz.
• LULI was able to achieve more than 10 joules at 2Hz with a water jets cooled Yb:YAG disk amplifier.
• CELIA developed a 47 fs photonic rod laser system delivering 8.6 W average power.
  

Activities for objective 2 (parametric conversion) were dedicated  to non-linear combination, ultra-high contrast and OPCPA optically synchronized schemes:

• STFC developed a Joule level/35 fs laser system with a contrast after compression measured at 106 at 10ps and 1011 at 5ns.
• GSI reduced ASE with pulses partly stretched early in itsamplifier chain.
• CEA measured thermal lensing in Ytterbium doped sesquioxides thin-disks lasers at low temperature and estimated the associated radiative quantum efficiency
• CNR added an OPCPA preamplifier stage to its BLISS laser system while
• VULCR developed a high contrast NIR OPCPA system with an enhanced signal/ASE energy contrast.
• Finally, USZ developed a 150 fs 200 μJ source whereas
• PIVUT developed a mid-IR 3.9 μm OPCPA delivering 12-mJ 80 fs pulses at 20 Hz.

Activities for objective 3 (coherent aperture combination) were essentially dedicated to non-linear conversion schemes: STFC achieved two beam CW spatial coherence and temporal coherence in femtosecond pulses while CEA developed a numerical code to calculate phasematching loci and associated angular tolerances in arbitrary geometries. VULRC developed a pump laser system for multi-beam energy combination in an OPA relying on 3 ns fiber amplifiers and INFLPR studied spectral coherent combination of ultrashort pulses and experimentally demonstrated non-linear power addition using spectral combination.

STFC laser testbed for contrast studies

Jean-Christophe Chanteloup