1. Highly efficient Raman fiber laser Collaborators: E. Bélanger M. Bernier B. Déry D. Faucher Réal Vallée

2. OUTLINE I: Raman scattering and gain II: Raman fiber lasers (two generations) III: Standard Model IV: Experimental set-up V: Results & discussion VI: Conclusion

3. I: Raman fiber laser (RFL)

4. Raman scattering Spontaneous Stimulated

5. D.J. Dougherty, et al. Opt. Lett. 20, (1995) 31-33. Raman gain spectrum @ = 1μm

6. Pump Stokes Evolution of the Stokes and pump signals : Forward SRS

7. 2. Time-dispersion tuning: C. Lin et al. Appl. Phys. Lett. 31 (1977) 97-99 CW 1. Angular tuning: Raman fiber lasers: 1 st generation R. Stolen et al. Appl. Phys. Lett. 30, (1977) 340

8. Raman fiber lasers: 2 nd generation  Key elements were developed for the 2 nd generation of RFL Fiber Bragg gratings providing reduced losses, spectral selectivity & tunability Low loss fibers standard or with high Ge or P content High power Ytterbium fiber lasers providing power, reliability and spectral bandwidth

9. Raman fiber lasers: 2 nd generation Nested cavities

10. Spectral coverage E.M. Dianov et al., Quantum Electron. 35, 435-441 (2005)

11. PpPp PsfPsf PsbPsb P p IN P s OUT 0 L Z P p IN P s OUT R1R1 R2R2 1108nm 1165nm Bragg gratings Standard numerical model

12.  Boundary conditions: Standard numerical model  Propagation equations:

13. R IC = 99% Laser optimisation vs R OC

14. Laser optimisation vs L R IC = 99% R OC = 26%

15. II: Highly efficient FRL

16. (15 W) Corning HI980 (9% Ge) Experimental set-up

17. Pump Stokes

18. Parameters used in simulationOC1 configurationOC2 configuration Fiber attenuation losses @ p 0.941 dB/km Fiber attenuation losses @ s 0.811 dB/km Splicing losses0.03 dB IC gray losses0.04 dB IC cladding-mode losses @ s  eff OC gray losses0.01 dB OC cladding-mode losses @ s 0.00 dB IC reflectivity99.6 % OC reflectivityR eff /55 %R eff /26 %

19. Spectral broadening

20. First configuration: OC1

21. Laser curve with OC1

22. Stokes vs absorbed pump with OC1

23. Second configuration: OC2 IC OC2

24. Laser curve with OC2

25. Stokes vs absorbed pump with OC2

26. Effective reflectivity

27. Effective reflectivity (OC2)

28. Cladding-mode losses (IC)

30. Effective losses (IC/OC2)

31. Laser curve with OC2

32. Tuning of FBGs : Set-up

33. Tuning curve

34. Conclusion  RFL with efficiencies approaching quantum limit can be obtained using well designed FBGs.  The standard model (AuYeung & Yariv) can be used provided effective R and  are considered.  10 W output is achievable from an optical fiber with a moderate Ge content.  Tunability over tens of nm is expected.