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Johan Boullet 1 *, Nicholas Traynor 2 , and Eric Cormier 1

Johan Boullet 1 *, Nicholas Traynor 2 , and Eric 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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Johan Boullet 1 *, Nicholas Traynor 2 , and Eric Cormier 1

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  1. Johan Boullet1*, Nicholas Traynor2 , and Eric Cormier1 1Université de Bordeaux-CNRS-CEA, Centre Lasers Intenses et Applications (CELIA), 351 cours de la Libération F-33405 Talence, France 2Alphanov, Centre Technologique Optique et Lasers, 351 Cours de la Libération - 33405 Talence – France *Corresponding author: boullet@celia.u-bordeaux1.fr Invited Talk 7721A-6 : 16 W at 488 nm by frequency doubling of a high energy pulsed three-level Yb-doped fiber laser

  2. Outline of the talk • Applications of 976 nm / 488 nm laser sources • Theoretical background of three-level operation of Yb-doped material • High Power CW 977 nm fiber laser • High Energy pulsed fiber laser @ 977 nm • High Energy Blue Fiber Laser @ 488 nm • Outlooks and conclusions

  3. Potential applications of HP 976 nm laser sources ? Bright Pumping of Yb-doped materials Laser Surgery TELECOM (EDFA Pumping) • TELECOM (EDFA) • Laser surgery (skin absorption *3 @ 977 nm compared to 1064 nm. TELECOM (EDFA Pumping)

  4. Potential applications of HP 976 nm laser sources ? Bright Pumping of Yb-doped materials Laser Surgery • TELECOM (EDFA) • Laser surgery (skin absorption *3 @ 977 nm compared to 1064 nm. • Ultra-Bright Pumping of Rare-Earth Doped of bulk/fiber oscillators/amplifiers : TELECOM (EDFA Pumping) High brightness Pump =>Shorter Absorption length=>Reduced non linearities=> Increased performances of Yb based fs Systems!!!

  5. Potential applications of HP 488 nm laser sources ? Bright Pumping of Yb-doped materials TELECOM (EDFA Pumping) • Replacement of Ar ion lasers (size, low efficiency, maintenance). • Biophotonics • DNA sequencing • Flux Citometry Food industry Under-Sea Communications

  6. State of the art of actual technologies for single mode high power laser sources emitting at 976 nm? • Laser Diode (~0.5 - 3W) • OPSL (Typically 5 W) • VCSEL (Demonstration of 30W, typically 10W)

  7. State of the art of actual technologies for single mode high power laser sources emitting at 976 nm? • Laser Diode (~1W) • OPSL (Typically 5 W) • VCSEL (Demonstration of 30W, typically 10W) • Yb DOPED LASER MATERIAL… Emission and absorption cross section of Yb in a silica matrix

  8. State of the art of actual technologies for single mode high power laser sources emitting at 976 nm? • Laser Diode (~1W) • OPSL (Typically 5 W) • VCSEL (Demonstration of 30W, typically 10W • Yb DOPED LASER MATERIAL… State of the art up to 2008… Up to 1.4 W at 985 nm… Emission and absorption cross section of Yb in a silica matrix

  9. State of the art of actual technologies for single mode high power laser sources emitting at 976 nm? • Laser Diode (~1W) • OPSL (Typically 5 W) • VCSEL (Demonstration of 30W, typically 10W • Yb DOPED LASER MATERIAL… State of the art up to 2008… Up to 1.4 W at 985 nm… Up to 4.3W at 976 nm… Emission and absorption cross section of Yb in a silica matrix * [K.H. Ylä-Jarkko et al., "A 3,5 W 977 nm cladding-pumped jacketed-air clad ytterbium-doped fiber laser", in Proc. Advanced Solid State Photonics, San Antonio, TX, Feb 3-5, 2003, Postdeadline Paper PD 2]

  10. Emission and absorption cross section of Yb in a silica matrix

  11. True 3-level Operation in the 970 nm- 980 nm 2F5/2 ls=1030-1080nm lp= 915 nm λs=976 nm 2F7/2 Emission and absorption cross section of Yb in a silica matrix

  12. 1 Transparency of the amplifying medium Transparency population inversion: Achieved for a transparency pump intensity of: ssabs ssem ~ssabs ssem ssabs ssem Transparency at 1030 nm achieved for inversion ~5% …

  13. 2 Gain competition between quasi and true 3-level laser operation : Large b will lead to negligible gain at 976 compare to 1030 Clad to core area ratio Pump absorption Typical commercially available DC LMA fiber for high power operation : 30 / 250 µm β=70 αp=1 dB => G1030 nm=50 dB Even for 20 % of absorbed pump power, ASE at 1030 nm will dominate laser operation at 977 nm!!!

  14. 2 Gain competition between quasi and true 3-level laser operation : Large b will lead to negligible gain at 976 compare to 1030 Clad to core area ratio Pump absorption - ORC proposed in 2003 a specific DC fiber with a pump-clad diameter limited at 20 µm (Φcore=9 µm) β=8 :αp=9 dB => G1030 nm< 50 dB Φclad=20 µm=> Pp ~ few W * [K.H. Ylä-Jarkko et al., "A 3,5 W 977 nm cladding-pumped jacketed-air clad ytterbium-doped fiber laser", in Proc. Advanced Solid State Photonics, San Antonio, TX, Feb 3-5, 2003, Postdeadline Paper PD 2]

  15. 2 Gain competition between quasi and true 3-level laser operation : Large b will lead to negligible gain at 976 compare to 1030 Clad to core area ratio Pump absorption - ROD TYPE U-LMA PCF β=8 :αp=9 dB => G1030 nm< 50 dB Φclad=200 µm => Pp ~ several 100W

  16. 2 Gain competition between quasi and true 3-level laser operation : Large b will lead to negligible gain at 976 compare to 1030 Clad to core area ratio Pump absorption - ROD TYPE U-LMA PCF 100 W-class fiber laser at 977 nm seems feasible !!! β=8 :αp=9 dB => G1030 nm< 50 dB Φclad=200 µm => Pp ~ several 100W

  17. High Power CW 3-level 977 nm Fiber Laser

  18. Rod type fiber : Microstructured Double clad Yb doped 80µm/200µm Absorption: 10 dB/m Length : 1.2 m Boullet et al., OE 16, 17891 (2008)

  19. - Standard in line fiber laser architecture • Cavity closed by : • DM on one side (Rmax@977 nm, 30 dB losses at 1030 nm) • Polished fiber end on the other side Boullet et al., OE 16, 17891 (2008)

  20. A second intra-cavity spectral filter (Tmax@ 977 nm, 30 dB losses at 1030 nm) Increases the losses at 1030 nm up to 60 dB… Boullet et al., OE 16, 17891 (2008)

  21. Laser is delivered by a DM and unabsorded pump light is recycled at the cavity end… Boullet et al., OE 16, 17891 (2008)

  22. Experimental Results M2 <1.35 at 94 W 94 W !!!

  23. 977.5 nm Parasitic lasing suppression : ASE 35 dB

  24. These performances represent a strong breakthrough in the 976 nm laser sources technology. • Can these performances be easilly transferred to pulsed operation?

  25. High Energy 3-level 977 nm Fiber Laser Boullet et al., OE 16, 17891 (2008)

  26. Spectral Covering of High Energy ns Fiber laser 2010 : State of the art of high energy nanosecond fiber based sources

  27. Spectral Covering of High Energy ns Fiber laser At 1 µm, Yb-doped Fiber based systems Jena University, 2002 MOPA Jena University, 2005 Oscillator

  28. Spectral Covering of High Energy ns Fiber laser At 1 µm, Yb-doped Fiber based systems 80 µm core Yb-doped fiber commercialy available !!!! Jena University, 2002 MOPA Jena University, 2005 Oscillator

  29. Spectral Covering of High Energy ns Fiber laser SHG 532 nm , THG, 355 nm SHG, THG 80 µm core Yb-doped fiber commercialy available !!!! MOPA Oscillator

  30. Spectral Covering of High Energy ns Fiber laser At 1.5 µm, Er-doped Fiber based systems (eye safe window, coherent LIDAR application) ACULIGHT, 2008 MULTIFILAMENT Er-doped FIBER, ONERA & IPHT 2008 ONERA, 2008

  31. Spectral Covering of High Energy ns Fiber laser At 2 µm, Tm-doped Fiber based systems The next revolution?

  32. Spectral Covering of High Energy ns Fiber laser Anyway, there remains several spectral bands which are not covered by pulsed fiber laser….

  33. Spectral Covering of High Energy ns Fiber laser 977nm and 488 nm : HIGH ENERGY THREE LEVEL FIBER LASER !!!

  34. Spectral Covering of High Energy ns Fiber laser 977 nm and 488 nm : HIGH ENERGY THREE LEVEL Yb-doped FIBER LASER !!! • Khitrov, D. Machewirth, B.Samson, K. Tankala, Proc. Of SPIE vol 6102, paper 610222. (2006)

  35. Experimental setup Master Q-Switched Fiber Oscillator Power Fiber Amplifier Architecture

  36. Experimental setup Boullet et al., OE 16, 17891 (2008) • Cudtom air clad LMA Yb-doped fiber (L~1 m, PERFOS, France) • 10 ° angle on both fiber ends • ~60 dB intracavity losses @1030 nm

  37. Rod-Type Photonic Crystal Fiber main amplifier Rod type fiber : Microstructured Double clad Yb-doped 80µm/200µm Absorption: 10 dB/m Length : 1.2 m

  38. Master Fiber Oscillator Characterization %ASE = 58% Pulse energy = 43 µJ T= 35µs INTERPULSE ASE Roll of in the power versus frequency curve occur around 50 kHz…

  39. Master Fiber Oscillator Characterization 12 ns Δ = 12ns Very short pulses (12 ns, limited by the cavity round-trip) at very low energy level (~ 20 µJ) : very high single pass gain @ 977 nm…

  40. Rod-Type Main Amplifier Characterization At a fixed rep. rate 82 kHz of repetiton rate (shortest pulses, saturation of the main amplifier) Output Beam at 71 W @ 977 nm (M2<1.4)

  41. Rod-Type Main Amplifier Characterization ~ 25 dB

  42. Rod-Type Main Amplifier Characterization 96% of total output power in the 974-982 nm spectral bandwidth ~ 25 dB

  43. Rod-Type Main Amplifier Characterization Pulse train before amplification

  44. Rod-Type Main Amplifier Characterization Pulse train before amplification Pulse train before amplification Pulse train After Amplification at 71 W

  45. Rod-Type Main Amplifier Characterization • A non-negligible proportion of power is contained in INTERPULSE ASE at 977 nm produced IN THE MAIN AMPLIFIER. • The fraction of interpulse ASE was estimated through temporal integration to ~17% Pulse train before amplification Pulse train After Amplification at 71 W

  46. Rod-Type Main Amplifier Characterization • Short Pulse average power : 59 W • - Pulse Energy 0.7 mJ Pulse train before amplification Pulse train After Amplification at 71 W

  47. Rod-Type Main Amplifier Characterization • Short Pulse average power : 59 W • - Pulse Energy 0.7 mJ Pulse peak power 50 kW 12 ns Pulse train before amplification Pulse train After Amplification at 71 W

  48. Energy Extraction Scalability Operation at 10 kHz • Total output power : 45 W • %ASE : 78.5% • Pulse Average Power : 9.7 W • Pulse energy : 0.97 mJ • Pulse Peak Power : ~65 kW Pulse peak power 65 kW

  49. SHG : Experimental Setup f=125 mm λ/2 λ/4 DM LBO crystal IR HE 977 nm Fiber laser Output 59 W @ 977 nm Power measurement Blue Light W Non Optimized coating for 977 nm radiation • Waveplates non optimized for 977 nm radiation, • Non coated LBO Crystal • 10% of unpolarized fundamental light at the rod-type fiber output Only 44 W of Power available in the right polarization state available for SHG…

  50. SHG : Results f=125 mm λ/2 λ/4 DM LBO crystal IR HE 977 nm Fiber laser Output 59 W @ 977 nm Power measurement Blue Light W • Critically phase-matched type I LBO • Crystal dimension: 3x3x12 mm3 • Max. peak intensity at focus: 0.6 GW/cm2, 100 µm waist (f=125 mm)

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