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High Average Power, High Energy, Femto-second High Average Power, High Energy, Femto-second Fiber Chirped Pulse Amplification SystemFiber Chirped Pulse Amplification System
F. He, J. H. V. Price, A. Malinowski, A. Piper, M. Ibsen, D. J. Richardson Optoelectronics Research Centre
University of Southampton, Southampton, UK
J. W. Dawson, C. W. Siders, J. A. Britten, C. P. J. BartyLawrence Livermore National Laboratory, 700 East Avenue, Livermore, USA
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OutlineOutline
Background and motivationBackground and motivation
Experimental setupExperimental setup
Fiber oscillatorFiber oscillator
Chirped Fiber Bragg Grating (CFBG)Chirped Fiber Bragg Grating (CFBG)
Large Mode Area (LMA) fiberLarge Mode Area (LMA) fiber
Modelling tools for bandwidth optimizationModelling tools for bandwidth optimization
Dielectric grating compressorDielectric grating compressor
Experimental resultsExperimental results
Conclusion and future workConclusion and future work
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Background and MotivationBackground and Motivation Fiber Chirped Pulse Amplification (CPA) system with high-Fiber Chirped Pulse Amplification (CPA) system with high-
quality, high-energy femto-second pulses, at high average quality, high-energy femto-second pulses, at high average power.power. Applications: industrial materials processing, etc. Applications: industrial materials processing, etc. Fiber systems: high gain, compact and robust, less thermo-optical Fiber systems: high gain, compact and robust, less thermo-optical
problems at high power. problems at high power. Limitations: nonlinear Limitations: nonlinear
effectseffects CompactCompact
Fiber oscillator Fiber oscillator and stretcherand stretcher
The key for The key for achieving high achieving high
PPave ave + E+ E Dielectric gratingDielectric grating
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Experimental setupExperimental setup
Novel technologies:Novel technologies: Mode-Locked Fiber OscillatorMode-Locked Fiber Oscillator CFBG (designed with both 2CFBG (designed with both 2ndnd and 3 and 3rdrd order dispersion order dispersion
compensation matched to the compressor)compensation matched to the compressor) Modelling tools for bandwidth optimizationModelling tools for bandwidth optimization Dielectric GratingDielectric Grating
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Mode locked fiber oscillatorMode locked fiber oscillator
pump
HRSESAM
Yb+3
Fiber
Diode pumped Diode pumped Robust self start (SESAM)Robust self start (SESAM) Polarization rotation mode-Polarization rotation mode-
lockinglocking Pulse energy ~ 60pJ at Pulse energy ~ 60pJ at
~50 MHz~50 MHz Low amplitude noiseLow amplitude noise
See: L. LEFORT, et Al., Optics Letters, v27 pp291 (2002)
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Chirped Fiber Bragg GratingChirped Fiber Bragg Grating
Fiber stretcherFiber stretcher Designed with both 2nd and 3rd Designed with both 2nd and 3rd
order dispersion compensation order dispersion compensation matched to the compressormatched to the compressor
Bandwidth ~12nmBandwidth ~12nm ~2.5dB reflectivity variation~2.5dB reflectivity variation Minimal spectral ripple Minimal spectral ripple
(measured at 0.01nm (measured at 0.01nm resolution)resolution)
See also: G.IMESHEV, Optics Letters, v29 pp679
(2004)
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Large Mode Area FiberLarge Mode Area Fiber
Core: diameter=20Core: diameter=20µµm, N.A.=0.06m, N.A.=0.06 Inner cladding: diameter=200Inner cladding: diameter=200µµm, N.A.=0.5m, N.A.=0.5 V=3.77V=3.77 Output MOutput M22~1.06 at bending diameter~11cm~1.06 at bending diameter~11cm Slope efficiency ~77%Slope efficiency ~77%
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Bandwidth ModellingBandwidth Modelling A modelling tool was used for predicting the performance of coA modelling tool was used for predicting the performance of complexmplex Yb- Yb-
fiber amplifierfiber amplifier system systems (prediction accuracy shown for single amplifiers s (prediction accuracy shown for single amplifiers below).below).
Simulations were applied to the design of our broad bandwidth multi-Simulations were applied to the design of our broad bandwidth multi-stage stage amplifier amplifier systemsystem..
See: F.HE, et Al., Optics Express v14 pp12846 (2006)
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Dielectric GratingDielectric Grating Advantages:Advantages:
High efficiencyHigh efficiency High compression factor (larger size compared with silica High compression factor (larger size compared with silica
transmission gratings)transmission gratings) High damage threshold (~10 times of gold gratings)High damage threshold (~10 times of gold gratings) High average power handlingHigh average power handling
Specifications of the grating in useSpecifications of the grating in use Groove density ~1780 l/mmGroove density ~1780 l/mm Size ~10cm*20cmSize ~10cm*20cm Efficiency ~95%Efficiency ~95%
See: J.BRITTEN, et Al., QELS 2005, JFB5
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Experiment resultsExperiment results Average output power ~135 W (at final amplifier output)Average output power ~135 W (at final amplifier output)
Pulse energy ~13.5 Pulse energy ~13.5 µµJ (at repetition rate of 10 MHz)J (at repetition rate of 10 MHz)
Pulse FWHM ~360 fs (assuming Gaussian shape)Pulse FWHM ~360 fs (assuming Gaussian shape)
Time bandwidth product ~0.6Time bandwidth product ~0.6
Compressor overall transmission efficiency ~52%Compressor overall transmission efficiency ~52%
Spectral clipping due to the size of the grating (performance has been Spectral clipping due to the size of the grating (performance has been improved now)improved now)
(10 MHz)
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Progress and Future workProgress and Future work
Compressor optimizationCompressor optimization
Spectral clipping is removed by applying larger gratings and Spectral clipping is removed by applying larger gratings and mirrorsmirrors
Nonlinear effectsNonlinear effects
SPMSPM B-integral ~ B-integral ~ ππ @13.5 @13.5µµJJ
Pulse distortion observed @20Pulse distortion observed @20µµJJ
SRSSRS We observed at pulse energy ~ 200We observed at pulse energy ~ 200µµJJ
Future workFuture work
System with high average power (>100W) System with high average power (>100W)
and high pulse energy (>100 and high pulse energy (>100 µµJ).J).
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ConclusionConclusion
We demonstrated an Yb-fiber CPA system incorporating a We demonstrated an Yb-fiber CPA system incorporating a CFBG stretcher, a cascaded chain of bandwidth-optimised CFBG stretcher, a cascaded chain of bandwidth-optimised amplifiers and a dielectric grating compressor. amplifiers and a dielectric grating compressor.
The system produced 135 W average power with pulse energy The system produced 135 W average power with pulse energy of 13.5 µJ. The recompressed pulse duration was 360 fs. of 13.5 µJ. The recompressed pulse duration was 360 fs.
Robust source of high pulse energies at high average powers Robust source of high pulse energies at high average powers should further broaden the applications of femto-second fiber-should further broaden the applications of femto-second fiber-based CPA systems.based CPA systems.