1. Developing Continuous-Wave Raman Lasers in Solid para- Hydrogen and Barium Nitrate William R. Evans Benjamin J. McCall Takamasa Momose Department of Physics University of Illinois at Urbana-Champaign Departments of Chemistry, Astronomy and Physics University of Illinois at Urbana-Champaign Department of Chemistry The University of British Columbia

2. Eventual Goal: Mid-Infrared Spectroscopy Many Attractive Targets in 5 – 10 μm Range Animation from Joel Bowman, Emory University C 60 C3H3+C3H3+ CH 5 + 22 June 2012 http://bjm.scs.illinois.edu 2

3. Eventual Goal: Mid-Infrared Spectroscopy Many Attractive Targets in 5 – 10 μm Range Few Available Widely-Tunable Laser Sources  Want sub-MHz resolution  Necessitates cw sources 22 June 2012 http://bjm.scs.illinois.edu 3

4. Eventual Goal: Mid-Infrared Spectroscopy Many Attractive Targets in 5 – 10 μm Range Few Available Widely-Tunable Laser Sources Stimulated Raman Scattering  Shifting a near-infrared laser into the mid-infrared 22 June 2012 http://bjm.scs.illinois.edu 4

5. Brief Review of Raman Scattering Pump photon scatters inelastically with an atom  Redshifted to a “Stokes” photon. 22 June 20125

6. Stimulated Raman Scattering Two-photon process Incoming Stokes stimulates transition Outgoing photons emitted coherently 22 June 20126

7. Stimulated Raman Scattering Optical cavity enhances process 22 June 20127

8. Stimulated Raman Scattering Optical cavity enhances process Collect either:  Just Stokes Radiation 22 June 20128

9. Stimulated Raman Scattering Optical cavity enhances process Collect either:  Just Stokes Radiation  Both Pump and Stokes Radiation 22 June 20129

10. Key Criterion: Threshold Pump Power 22 June 2012 http://bjm.scs.illinois.edu 10

11. Key Criterion: Threshold Pump Power Want:  Ultra-narrow linewidth  Need cw laser  Not high complexity  Lower finesse cavity Challenges:  CW pump lasers have lower maximum power  Lower finesse cavity means less power buildup in the cavity 22 June 2012 http://bjm.scs.illinois.edu 11

12. Key Criterion: Threshold Pump Power How we are going to achieve lasing:  Need high Raman gain coefficient 22 June 2012 http://bjm.scs.illinois.edu 12

13. Options: Solid para-Hydrogen and Barium Nitrate 22 June 2012 http://bjm.scs.illinois.edu 13

14. Options: Solid para-Hydrogen and Barium Nitrate Transparent for most of 100 nm to 10 μm M. Fushitani, S. Kuma, Y. Miyamoto, H. Katsuki, T. Wakabayashi, T. Momose, and A.F. Vilesov, Optics Letters, 28, 1, 37 (2003) M. Mengel, B.P. Winnewisser, and M. Winnewisser, Canadian Journal of Physics, 78, 317 (2000)

15. Options: Solid para-Hydrogen and Barium Nitrate Transparent for most of 100 nm to 10 μm Huge Raman gain  18,000 cm/GW  Compare: 2.5 cm/GW for gaseous hydrogen 47 cm/GW for Ba(NO 3 ) 2 M. Fushitani, S. Kuma, Y. Miyamoto, H. Katsuki, T. Wakabayashi, T. Momose, and A.F. Vilesov, Optics Letters, 28, 1, 37 (2003) M. Mengel, B.P. Winnewisser, and M. Winnewisser, Canadian Journal of Physics, 78, 317 (2000)

16. Options: Solid para-Hydrogen and Barium Nitrate Transparent for most of 100 nm to 10 μm Huge Raman gain  18,000 cm/GW Enormous frequency shift  4149.7 cm -1 in solid http://bjm.scs.illinois.edu 16

17. Options: Solid para-Hydrogen and Barium Nitrate Transparent for most of 100 nm to 10 μm Huge Raman gain  18,000 cm/GW Enormous frequency shift  4149.7 cm -1 in solid Well-established as a Raman medium 22 June 2012 http://bjm.scs.illinois.edu 17

18. Options: Solid para-Hydrogen and Barium Nitrate Transparent for most of 100 nm to 10 μm Huge Raman gain  18,000 cm/GW Enormous frequency shift  4149.7 cm -1 in solid Well-established as a Raman medium Highest Raman gain of any room-temp crystal  47 cm/GW 22 June 2012 http://bjm.scs.illinois.edu 18

19. Options: Solid para-Hydrogen and Barium Nitrate Transparent for most of 100 nm to 10 μm Huge Raman gain  18,000 cm/GW Enormous frequency shift  4149.7 cm -1 in solid Well-established as a Raman medium Highest Raman gain of any room-temp crystal  47 cm/GW Frequency shift of 1047 cm –1 http://bjm.scs.illinois.edu 19

20. Long-Range Goal: Fully-optimized solid para-hydrogen cw Raman laser tunable between 5 and 10 μm  Achievable by pumping with the signal beam from a cw OPO which is tunable from 1.6 to 1.9 μm Threshold pump power can be minimized by using actively-locked doubly-resonant high-finesse optical cavity 22 June 2012 http://bjm.scs.illinois.edu 20

21. Barium Nitrate is a Natural Preparatory Project Despite its obvious promise, solid para-hydrogen has never been used as a cw Raman shifter. Constructing an actively-locked doubly-resonant cavity involves some technical complexity that we want to separate from the complexity involved in making a cryogenic crystal. Barium nitrate is a natural preparatory project. An actively-locked doubly-resonant barium nitrate Raman shifter has never been constructed. 22 June 2012 http://bjm.scs.illinois.edu 21

22. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics 22 June 2012 http://bjm.scs.illinois.edu 22

23. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics Dry N 2 Purge Box Ba(NO 3 ) 2 Crystal 22 June 2012 http://bjm.scs.illinois.edu 23

24. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics Dry N 2 Purge Box Ba(NO 3 ) 2 Crystal 22 June 2012 http://bjm.scs.illinois.edu

25. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics Dye Laser 22 June 2012 http://bjm.scs.illinois.edu 25

26. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics Dye Laser Coherent 899 Dye Ring Laser 22 June 2012

27. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics 22 June 2012 http://bjm.scs.illinois.edu 27

28. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics 22 June 2012

29. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 Crystal 22 June 2012 http://bjm.scs.illinois.edu 29

30. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics EOM 22 June 2012 http://bjm.scs.illinois.edu 30

31. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics EOM New Focus Model 4001 Electro-Optic Phase Modulator 22 June 2012

32. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics EOM 22 June 2012 http://bjm.scs.illinois.edu 32

33. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics EOM 22 June 2012 http://bjm.scs.illinois.edu 33

34. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics EOM 22 June 2012 http://bjm.scs.illinois.edu 34

35. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics EOM Cavity Transmission Error Signal 22 June 2012

36. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics PZT 22 June 2012 http://bjm.scs.illinois.edu 36

37. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics PZT 22 June 2012 http://bjm.scs.illinois.edu

38. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics AOM ¼ λ 22 June 2012 http://bjm.scs.illinois.edu 38

39. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics AOM ¼ λ Locking Electronics Brimrose EM-85-2-1064 Acousto-Optic Modulator 22 June 2012 http://bjm.scs.illinois.edu 39

40. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics 22 June 2012 http://bjm.scs.illinois.edu 40

41. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Dye Laser Dry N 2 Purge Box Ba(NO 3 ) 2 CrystalPZT EOM Locking Electronics Cryostat Solid p-H 2 Crystal 22 June 2012 http://bjm.scs.illinois.edu 41

42. AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Pump Laser PZT EOM Locking Electronics Cryostat Solid p-H 2 Crystal 22 June 2012 http://bjm.scs.illinois.edu 42

43. AOM ¼ λ First Continuous-Wave Solid para-Hydrogen Raman Laser Pump Laser PZT EOM Locking Electronics Cryostat Solid p-H 2 Crystal First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser 22 June 2012 http://bjm.scs.illinois.edu 43

44. AOM ¼ λ First Continuous-Wave Solid para-Hydrogen Raman Laser Pump Laser PZT EOM Locking Electronics Cryostat Solid p-H 2 Crystal 22 June 2012 http://bjm.scs.illinois.edu 44

45. Summary Solid para-hydrogen is an attractive medium for use in stimulated Raman scattering. A solid para-hydrogen Raman laser pumped by a cw OPO can cover the 5 – 10 μm portion of the spectrum. We are constructing the first actively-locked doubly-resonant barium nitrate Raman laser in the visible in preparation for building this system. 22 June 2012 http://bjm.scs.illinois.edu 45

46. Acknowledgments McCall Research Group Steve Kregel Preston Buscay Heather Hanson Kristin Evans The McCall Research Group http://bjm.scs.illinois.edu