X-CAN A coherent amplification network of femtosecond fiber amplifiers Jean-Christophe Chanteloup, Louis Daniault LULI, Ecole Polytechnique, CNRS, CEA, UPMC, Route de Saclay, 91128, Palaiseau, France Gérard Mourou IZEST, Ecole Polytechnique, Route de Saclay, 91128, Palaiseau, France Jérome Bourderionnet, Arnaud Brignon Thales Research & Technology, 1 avenue Augustin Fresnel, 91767 Palaiseau, France
Femtosecond lasers and applications High power lasers => ultrashort pulses (fs) Peak Power Average Power (Repetition rate) P peak E t T P peak = E t T P average = E T Applications in fundamental physics: High-harmonics generation Isolated attoseconde pulses Ultrafast spectroscopy Time/frequency metrology Particle acceleration Ti:Sa crystals Yb-doped fibers Energy (10 J) (1 mj) Duration/bandwidth ( 10 fs) (100 fs) Repetition rate (10 Hz) (100 MHz) Overall efficiency (0.1 %) (30 %) 24/09/2014 LOUIS DANIAULT IZEST 2014 2
Laser-driven collider concept 24/09/2014 LOUIS DANIAULT IZEST 2014 3
Laser particle acceleration Requirements : (Darmstadt 2010) 24/09/2014 LOUIS DANIAULT IZEST 2014 4
Ytterbium-doped fibers Ytterbium ion : - Absorption - Emission 980 nm 2 F 5/2 1030 nm 2 F 7/2 Simple spectroscopy (2 levels, no upconversion) Small quantum defect (5 %) Efficient diode pumping => High average powers Broadband (fused silica => ~ 100 fs) => Femtosecond amplification Fiber geometry : Excellent thermal handling. Long interaction length : high gain. => High average powers Signal Pump Outter clad Diffraction-limited beams. Ease of use, robustness, compactness Inner clad (pump) Active core (signal) n 24/09/2014 LOUIS DANIAULT IZEST 2014 5
Fiber-related drawbacks High peak powers Long interaction length Tight confinement inside the fiber core Highly sensitive to nonlinear effects In the femtosecond regime: Kerr Effect Self-phase modulation Self-focusing ( ~ 4 MW peak power for fused silica) 24/09/2014 LOUIS DANIAULT IZEST 2014 6
Reducing the peak power Chirped-Pulse Amplification (CPA): Peak power: Oscillator Stretcher Amplifier Compressor ~ 100 kw => ~ 1 GW (x10 4 ) Enlarging core diameter: Core diameter : ~ 5 µm => ~ 100 µm (mode area x400) Larger core size Transverse multimode propagation State of the art: 830 W average @ 78 MHz (10 µj), 640 fs, 16 MW peak power Tino Eidam et al., "Femtosecond fiber CPA system emitting 830 W average output power," Opt. Lett. 35, 94-96 (2010) 10 W average @ 5 khz (2.2 mj), 480 fs, 3.8 GW peak power Tino Eidam et al., "Fiber chirped-pulse amplification system emitting 3.8 GW peak power," Opt. Express 19, 255-260 (2011) 24/09/2014 LOUIS DANIAULT IZEST 2014 7
Coherent Beam Combining Principle of coherent beam combining with N parallel amplifiers: Peak AND Average powers increased by a factor of N. Constant nonlinearity level (N independent). Preservation of the temporal/spectral profiles of the individual beams. Compatible with the femtosecond regime. 24/09/2014 LOUIS DANIAULT IZEST 2014 8
Combining architecures Filled aperture: Tiled Aperture: I x, y Amp 1 Amp 2 Amp 3 Amp 4 O S C I L L A T O R S P L I T T E R 2 x N Microlenses matrix Fiber matrix Near Field Detection I θ x, θ y Far Field High combination efficiency 2 N channels => (2 N - 1) combination steps Lower efficiency (pupil filling) Single combination step 24/09/2014 LOUIS DANIAULT IZEST 2014 9
Peak power vs. Average power Quick performance review: 830 W @ 78 MHz 16 MW (10 µj) 10 W @ 5 khz 3.8 GW (2.2 mj) Coherent beam combining: 530 W average @ 400 khz (1.3 mj), 670 fs, 1.8 GW peak power 530 W @ 400 khz 1.8 GW (1.3 mj) Arno Klenke et al., "530 W, 1.3 mj, four-channel coherently combined femtosecond fiber chirped-pulse amplification system," Opt. Lett. 38, 2283-2285 (2013) 24/09/2014 LOUIS DANIAULT IZEST 2014 10
Large-scale coherent beam combining : CAN G. Mourou, W. Brocklesby, J. Limpert, T. Tajima, Nature Photonics, April 2013 «The future of Accelerator is Fiber» 24/09/2014 LOUIS DANIAULT IZEST 2014 11
XCAN : ICAN demonstrator XCAN : large-scale coherent beam combining 61 91 coherently combined channels (aperture filling) : 10 mj @ 10 khz ~ 30 % wall plug efficiency 61 channels 37 channels 19 channels Prospects towards CAN : Identify and adress issues specific to the femtosecond regime Improve the efficiency and output power of the individual amplifiers Increase the number of channels ~1000 24/09/2014 LOUIS DANIAULT IZEST 2014 12
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