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High energy mode-locked fiber laser at 976 nm

High energy mode-locked fiber laser at 976 nm. G. Machinet 1 , J. Lhermite 1 , C. Lecaplain 2 , J. Boullet 1,3 , N. Traynor 3 , A. Hideur 2 , E. Cormier 1 1 Université de Bordeaux-CNRS-CEA, Centre Lasers Intenses et Applications (CELIA), 351 cours de la Libération F-33405 Talence, France

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High energy mode-locked fiber laser at 976 nm

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  1. High energy mode-locked fiber laser at 976 nm G. Machinet1, J. Lhermite1, C. Lecaplain2, J. Boullet1,3, N. Traynor3, A. Hideur2, E. Cormier1 1Université de Bordeaux-CNRS-CEA, Centre Lasers Intenses et Applications (CELIA), 351 cours de la Libération F-33405 Talence, France 2CNRS UMR 6614 CORIA, Université de Rouen, Avenue de l’Université, BP 12,76801 Saint Etienne du Rouvray, France 3Alphanov, Centre Technologique Optique et Lasers, 351 Cours de la Libération - 33405 Talence –France 4Azur Light Systems, 351 Cours de la Libération - 33405 Talence –France

  2. Summary Theoretical background Experimental setup Results Conclusion E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  3. Motivations Pr3+/Er3+/ Ho3+/Tm3+ Ho3+ Nd3+ Yb3+ Tm3+ Tm3+ Pr3+ Er3+ Er3+ Ho3+ Er3+ 4000 2400 2000 1600 2800 1200 800  [nm] 488 nm 976 nm 3-level operation of Yb-doped materials Frequency conversion Applications of high brightness intense sources at 976 nm Laser surgery Laser dentistery Supercontinuum generation Applications of high brightness intense sources at 488 nm Replacement of Ar ion lasers Laser surgery Dermatology E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  4. Quasi 3- versus 3-level systems Configuration 1 Yb-doped fiber 2F5/2 ls=1030 nm lp= 976 nm 2F7/2 E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  5. Quasi 3- versus 3-level systems Configuration 1 Configuration 2 Yb-doped fiber Yb-doped fiber 2F5/2 2F5/2 915 nm ls=1030 nm 1030 nm 976 nm lp= 976 nm 2F7/2 2F7/2 E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  6. Quasi 3- versus 3-level systems Configuration 1 Configuration 2 Yb-doped fiber Yb-doped fiber 2F5/2 2F5/2 915 nm ls=1030 nm 1030 nm 976 nm lp= 976 nm 2F7/2 2F7/2 3-level operation of Yb-doped material 5 E. Cormier, LMB6, ICONO'LAT 2010, Kazan E. Cormier , ICONO'LAT 2010, Kazan

  7. Main Issues 1 Transparency at 976 nm : Transparency is achieved if : for a pump intensity of: ssem ssem ~ssabs ssabs ssem ssabs Example: transparency at 1030 nm achieved for inversion of ~5% … Strong pumping required E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  8. Main issues f Core f Clad 2 Gain competition between quasi 3- and true 3-level systems: Clad to core area ratio Pump absorption Typical DC-LMA fiber 30/250 mm: β = 70, G1030 > 50 dB  Limited output power Talk LTuG4 “Rod Type” fiber 80/200 mm: β = 6, G1030 < 50 dB100 W CW * and Amplifier New custom LMA fiber 20 mm: β ≈ 20, G1030 < 50 dB10 W CW, 1 W Q-switch and Mode-lock Talk LTuG4 E. Cormier, LMB6, ICONO'LAT 2010, Kazan *Boullet et al., OE 16, 17891 (2008), Roeser et al. OE 16, 17310 (2008)

  9. Experimental setup Rmax l/2 l/4 Output l/2 1030 nm l/4 l/2 M2 Pump @ 915nm Rmax YDF M1 M3 Ring cavity All normal dispersion NL Polarization evolution Diode pumped Pump recycling Spectral filtering E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  10. Experimental setup Rmax l/2 l/4 Output l/2 1030 nm l/4 l/2 M2 Pump @ 915nm Rmax YDF M1 M3 • Custom air clad LMA Yb-doped fiber: • D=20 μm, L~0.85 m • Angle cleaved at 10 ° to avoid parasitic lasing Ring cavity All normal dispersion NL Polarization evolution Diode pumped Pump recycling Spectral filtering E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  11. Experimental setup Rmax l/2 l/4 Output l/2 1030 nm l/4 l/2 M2 Pump @ 915nm Rmax YDF M1 M3 • Unabsorbed pump recycling: • Dichroïc mirror • Rmax mirror Ring cavity All normal dispersion NL Polarization evolution Diode pumped Pump recycling Spectral filtering E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  12. Experimental setup Rmax l/2 l/4 Output l/2 1030 nm l/4 l/2 M2 Pump @ 915nm Rmax YDF M1 M3 • 1030 nm radiation filtering : • Dichroic mirrors • 30 dB losses Ring cavity All normal dispersion NL Polarization evolution Diode pumped Pump recycling Spectral filtering E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  13. Experimental setup • Non-linear polarization evolution: • Passive single mode fiber • D=6 μm, L=3 m • Set of wave plates • Polarizer Rmax l/2 l/4 Output l/2 1030 nm l/4 l/2 M2 Pump @ 915nm Rmax YDF M1 M3 Self-starting mode-locking Ring cavity All normal dispersion NL Polarization evolution Diode pumped Pump recycling Spectral filtering E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  14. Efficiency Far field h ≈ 6% • Single mode fiber • Excellent beam quality • High brightness Laser threshold≈ 1.5 W E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  15. Single pulse operation Single pulse operation achieved by decreasing pump power Spectral signature E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  16. Single pulse operation Autoco for t < 50 ps Fast photodiode for t > 50 ps Signal [a.u] Time [μs] Enforced single pulse operation up to 500 mW output power Temporal signature E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  17. Spectrum Dl1/2 = 5 nm 30 dB Dl1/e2 = 10 nm • Pav = 480 mW • n = 40.6 MHz • E = 11.8 nJ E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  18. Duration Compressed pulses Output pulses Dt = 402 fs = 1.41 x 285 fs Dt = 1.44 ps = 1.41 x 1.02 ps • Pav = 480 mW • n = 40.6 MHz • E = 11.8 nJ • Dl = 5 nm • Dt = 285 fs • Ecompressed = 6 nJ !!! • Ppeak = 21 kW 50 % compressor efficiency only !! Potentially 37 kW 17 E. Cormier, LMB6, ICONO'LAT 2010, Kazan E. Cormier , ICONO'LAT 2010, Kazan

  19. Simulations Intra cavity pulse evolution for 10 nJ energy SA : saturable absorber OC : output coupling and cavity losses T. Schreiber et al. OE 15, 8252 (2007) • SPM and dispersion in the single mode fiber • Pulse shaping dominated by gain filtering E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  20. Conclusion We have demonstrated a high energy mode-locked Yb fiber laser emitting at 976 nm with the following features: Average power : 480 mW Repetition rate : 40.6 MHz Energy per pulse : 11.8 nJ Bandwidth : 5 nm (10 nm at 1/e2) Output pulses : Dt = 1 ps Compressed pulses : Dt = 285 fs Peak power : 21 kW (potentially 37 kW) E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  21. Outlook Frequency doubling : femtosecond pulses at 488 nm Direct femtosecond amplification: high power sub 200 fs pulses at 976 nm Amplification in CPA architecture : up to 50 W sub 300 fs puses at 976 nm Frequency conversion to 488 nm and 325 nm of amplified pulses : ultra high power and peak power E. Cormier, LMB6, ICONO'LAT 2010, Kazan

  22. Acknowledgements E. Cormier, LMB6, ICONO'LAT 2010, Kazan

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