Developing Continuous-Wave Raman Lasers in Solid para -Hydrogen and Barium Nitrate

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 C60 CH5+ C3H3+ Animation from Joel Bowman, Emory University http://bjm.scs.illinois.edu

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 http://bjm.scs.illinois.edu

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 http://bjm.scs.illinois.edu

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

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

7. Stimulated Raman Scattering Optical cavity enhances process

8. Stimulated Raman Scattering Optical cavity enhances process Collect either: Just Stokes Radiation

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

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

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

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

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

14. Transparent for most of 100 nm to 10 μm Options: Solid para-Hydrogenand Barium Nitrate 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. 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(NO3)2 Options: Solid para-Hydrogenand Barium Nitrate 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. Transparent for most of 100 nm to 10 μm Huge Raman gain 18,000cm/GW Enormous frequency shift 4149.7 cm-1 in solid Options: Solid para-Hydrogenand Barium Nitrate http://bjm.scs.illinois.edu

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

18. 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 Options: Solid para-Hydrogen andBarium Nitrate http://bjm.scs.illinois.edu

19. Transparent for most of 100 nm to 10 μm Huge Raman gain 18,000cm/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 Options: Solid para-Hydrogen andBarium Nitrate http://bjm.scs.illinois.edu

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 http://bjm.scs.illinois.edu

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. http://bjm.scs.illinois.edu

22. Dry N2 Purge Box PZT Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Dye Laser Locking Electronics http://bjm.scs.illinois.edu

23. Dry N2 Purge Box Dry N2 Purge Box PZT Ba(NO3)2 Crystal Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Dye Laser Locking Electronics http://bjm.scs.illinois.edu

24. Dry N2 Purge Box Dry N2 Purge Box PZT Ba(NO3)2 Crystal Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Dye Laser Locking Electronics http://bjm.scs.illinois.edu

25. Dry N2 Purge Box PZT Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Dye Laser Dye Laser Locking Electronics http://bjm.scs.illinois.edu

26. Dry N2 Purge Box PZT Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Dye Laser Dye Laser Locking Electronics Coherent 899 Dye Ring Laser

27. Dry N2 Purge Box PZT Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Dye Laser Locking Electronics http://bjm.scs.illinois.edu

28. Dry N2 Purge Box PZT Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Dye Laser Locking Electronics

29. Dry N2 Purge Box Dry N2 Purge Box PZT Ba(NO3)2 Crystal Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Dye Laser Dye Laser Locking Electronics http://bjm.scs.illinois.edu

30. Dry N2 Purge Box PZT Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM EOM Dye Laser Locking Electronics http://bjm.scs.illinois.edu

31. Dry N2 Purge Box PZT Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM EOM Dye Laser Locking Electronics New Focus Model 4001 Electro-Optic Phase Modulator

32. Dry N2 Purge Box PZT Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM EOM Dye Laser Locking Electronics http://bjm.scs.illinois.edu

33. Dry N2 Purge Box PZT Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM EOM Dye Laser Locking Electronics http://bjm.scs.illinois.edu

34. Dry N2 Purge Box PZT Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM EOM Dye Laser Locking Electronics Locking Electronics http://bjm.scs.illinois.edu

35. Dry N2 Purge Box PZT Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser Cavity Transmission EOM EOM Error Signal Dye Laser Locking Electronics Locking Electronics

36. Dry N2 Purge Box PZT PZT Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Dye Laser Locking Electronics Locking Electronics http://bjm.scs.illinois.edu

37. Dry N2 Purge Box PZT PZT Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Dye Laser Locking Electronics Locking Electronics http://bjm.scs.illinois.edu

38. Dry N2 Purge Box PZT Ba(NO3)2 Crystal AOM AOM ¼ λ ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Dye Laser Locking Electronics Locking Electronics http://bjm.scs.illinois.edu

39. Dry N2 Purge Box PZT Ba(NO3)2 Crystal AOM AOM ¼ λ ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Dye Laser Locking Electronics Locking Electronics Brimrose EM-85-2-1064 Acousto-Optic Modulator http://bjm.scs.illinois.edu

40. Dry N2 Purge Box PZT Ba(NO3)2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Dye Laser Locking Electronics http://bjm.scs.illinois.edu

41. Dry N2 Purge Box Cryostat PZT Ba(NO3)2 Crystal Solid p-H2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Dye Laser Locking Electronics http://bjm.scs.illinois.edu

42. Cryostat PZT Solid p-H2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser EOM Pump Laser Locking Electronics http://bjm.scs.illinois.edu

43. Cryostat PZT Solid p-H2 Crystal AOM ¼ λ First Actively-Locked Doubly-Resonant Barium Nitrate Raman Laser First Continuous-Wave Solid para-Hydrogen Raman Laser EOM Pump Laser Locking Electronics http://bjm.scs.illinois.edu

44. Cryostat PZT Solid p-H2 Crystal AOM ¼ λ First Continuous-Wave Solid para-Hydrogen Raman Laser EOM Pump Laser Locking Electronics http://bjm.scs.illinois.edu

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. http://bjm.scs.illinois.edu

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