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

Eventual Goal: Mid-Infrared Spectroscopy Many Attractive Targets in 5 – 10 μm Range Animation from Joel Bowman, Emory University C 60 C3H3+C3H3+ CH June

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

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

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

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

Stimulated Raman Scattering Optical cavity enhances process 22 June 20127

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

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

Key Criterion: Threshold Pump Power 22 June

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

Key Criterion: Threshold Pump Power How we are going to achieve lasing:  Need high Raman gain coefficient 22 June

Options: Solid para-Hydrogen and Barium Nitrate 22 June

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)

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)

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  cm -1 in solid 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  cm -1 in solid Well-established as a Raman medium 22 June

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  cm -1 in solid Well-established as a Raman medium Highest Raman gain of any room-temp crystal  47 cm/GW 22 June

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  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 19

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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 Acousto-Optic Modulator 22 June

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

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

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

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

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

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

Acknowledgments McCall Research Group Steve Kregel Preston Buscay Heather Hanson Kristin Evans The McCall Research Group