william r. evans benjamin j. mccall takamasa momose
DESCRIPTION
Toward a Continuous-Wave Solid para -Hydrogen Raman Laser for Molecular Spectroscopy Applications. William R. Evans Benjamin J. McCall Takamasa Momose. Department of Physics University of Illinois at Urbana-Champaign Departments of Chemistry, Astronomy and Physics - PowerPoint PPT PresentationTRANSCRIPT
Toward a Continuous-Wave
Solid para-Hydrogen Raman Laser for Molecular Spectroscopy Applications
William R. Evans
Benjamin J. McCall
Takamasa Momose
Department of PhysicsUniversity of Illinois at Urbana-Champaign
Departments of Chemistry, Astronomy and PhysicsUniversity of Illinois at Urbana-Champaign
Department of ChemistryThe University of British Columbia
Outline
Motivation for the Project Stimulated Raman Scattering Hydrogen as a Raman Medium Measuring the Index of Refraction of Solid para-Hydrogen
Current Progress Toward a cw Solid para-Hydrogen Raman Laser in the Visible
Future Plans and Summary
Mid-Infrared Spectroscopy
Many Attractive Targets in 5 – 10 μm Range Few Available Laser Sources
Astrochemistry need sub-MHz linewidth Need for cw sources
Possible Solution: Solid para-H2 Raman Laser Transparent for most of 100 nm to 10 μm
Enormous frequency shift 4155.2 cm-1 in gas 4149.7 cm-1 in solid
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)
Brief Review of Raman Scattering Pump photon scatters inelastically with an atom Redshifted to a “Stokes” photon.
Stimulated Raman Scattering Two-photon process Incoming Stokes stimulates transition Outgoing photons emitted coherently Efficiency of SRS depends on intracavity
power and Raman gain coefficient
Previous Work with Hydrogen
Gas Solid P
ulse
dC
ontin
uous
Previous Work with Hydrogen
Gas Solid1980, 1986: pulsed dye laser tunable from 1-10 μm 0.2 cm-1 linewidth P
ulse
dC
ontin
uous
A. DeMartino, R. Frey, and F. Pradere, IEEE J. QUANT. ELEC., VOL. QE-16, 11 (1980)P. Rabinowitz, B. N. Perry, and N. Levinos, IEEE J. Quantum Electron. 22, 797 (1986)
Previous Work with Hydrogen
Gas Solid1980, 1986: pulsed dye laser tunable from 1-10 μm 0.2 cm-1 linewidth
2003 – 2004: pulsed Nd:YAG, OPO Raman in both solid and liquid tunable from 4.4-8 μm 0.3 – 0.4 cm-1 linewidthP
ulse
dC
ontin
uous
M. Fushitani, S. Kuma, Y. Miyamoto, H. Katsuki, T. Wakabayashi, T. Momose, and A.F. Vilesov, Optics Letters, 28, 1, 37 (2003)B.J. McCall, A.J. Huneycutt, R.J. Saykally, C.M. Lindsay, T. Oka, M. Fushitani, Y. Miyamoto, and T. Momose, Applied Physics Letters, 82, 9, 1350 (2003)K.E. Kuyanov, T. Momose, and A.F. Vilesov, Applied Optics, 43, 32, 6023 (2004)
Previous Work with Hydrogen
Gas Solid1980, 1986: pulsed dye laser tunable from 1-10 μm 0.2 cm-1 linewidth
2003 – 2004: pulsed Nd:YAG, OPO Raman in both solid and liquid tunable from 4.4-8 μm 0.3 – 0.4 cm-1 linewidth
1998 – 2002: 1-2 mW pump threshold 4 kHz linewidth doubly-resonant cavity F ~ 50,000
Pul
sed
Con
tinuo
us
J.K. Brasseur, K.S. Repasky, and J.L. Carlsten, Optics Letters, 23, 5, 367 (1998)J.K. Brasseur, P.A. Roos, K.S. Repasky, and J.L. Carlsten, Journal of the Optical Society of America B, 16, 8, 1305 (1999)L.S. Meng, K.S. Repasky, P.A. Roos, and J.L. Carlsten, Optics Letters, 25, 7, 472 (2000)L.S. Meng, P.A. Roos, K.S. Repasky, and J.L. Carlsten, Optics Letters, 26, 7, 426 (2001)(and others)
Previous Work with Hydrogen
Gas Solid1980, 1986: pulsed dye laser tunable from 1-10 μm 0.2 cm-1 linewidth
2003 – 2004: pulsed Nd:YAG, OPO Raman in both solid and liquid tunable from 4.4-8 μm 0.3 – 0.4 cm-1 linewidth
1998 – 2002: 1-2 mW pump threshold 4 kHz linewidth doubly-resonant cavity F ~ 50,000
Pul
sed
Con
tinuo
us
Tradeoff Want:
Narrow linewidth Need cw laser Not high complexity Lower finesse cavity
Drawbacks: CW pump lasers have lower maximum power Lower finesse cavity means less power buildup in
the cavity Both of these factors make lasing more difficult
Tradeoff: Need high Raman gain coefficient Solid para-H2
Solid para-H2 Raman Gain Coefficient
H2 Gas p-H2 Crystal
n 2.50×1020 cm-3 2.64×1022 cm-3
Γ 300 MHz 8.4 MHz
M. Katsuragawa and K. Hakuta, Optics Letters, 25, 3, 177 (2000)
Solid para-H2 Raman gain coefficient measured by Katsuragawa and Hakuta ~ 7,000x that of gaseous hydrogen
Narrow linewidth because solid para-H2 is a quantum crystal
Index of Refraction of Solid para-H2 To design a solid para-H2 Raman laser, we
needed to know the index of refraction of solid para-H2.
Surprisingly, this quantity had never been reported before.
M. Perera, et al, Optics Letters, 36, 6, 840 (March 15, 2011)
Index of Refraction of Solid para-H2
Measurement Setup Incoming laser is refracted at slanted window. By measuring the exit angle of the laser, we
can determine the index of the solid para-H2 using Snell’s law.
M. Perera, et al, Optics Letters, 36, 6, 840 (March 15, 2011)
Stainless steel cell
OFHC copper connected to cold head
Sapphire windows
Laser
Index of Refraction of Solid para-H2
Results
M. Perera, et al, Optics Letters, 36, 6, 840 (March 15, 2011)
Solid para-H2 Raman LaserExperimental Setup With the index of refraction of solid para-H2 in
hand, we can design the setup for our laser. 1st Stage of Project:
Raman shifting in the visible: 514 nm 654 nm Multi-mode pump laser Singly-resonant cavity
(only building up Stokes radiation) No active cavity locking
Solid para-H2 Raman LaserExperimental Setup
Solid para-H2 Raman LaserExperimental Setup
Solid para-H2 Raman LaserExperimental Setup
Interfaces designed to be at Brewster’s angle. Minimize reflective scattering losses inside cavity.
Because np-H2 is greater than 1, the windows on the cell need to be wedged.
Solid para-H2 Raman LaserCell Design
Solid para-H2 Raman LaserExperimental Setup
Solid para-H2 Raman LaserExperimental Setup
Solid para-H2 Raman LaserCavity Design Specialty coated cavity
mirrors 1 m Radius of Curvature High transmitting at pump wavelength
(T ~ 98% at 514 nm) High reflecting at Stokes wavelength
(R = 99.5% at 654 nm) Cavity length 50 cm Diffraction grating used to separate pump
beam from Stokes beam after the cavity
Solid para-H2 Raman LaserCurrent Progress Solid para-H2 crystal grown
in new cell Pump laser through the
crystal windows properly aligned
Raman output within the next few weeks
Solid para-H2 Raman LaserFuture Plans Active cavity locking Single-mode pump laser Doubly-resonant cavity Raman lasing in the infrared
Summary Solid para-H2 is an attractive material for use as a
Raman gain medium. A fully-optimized solid para-H2 Raman laser could
potentially provide the first widely tunable laser source for ultra high resolution spectroscopy in the 5-10 μm range.
We have made the first ever measurements of the index of refraction of solid para-H2.
We have successfully designed and built a system that should be able to achieve Stokes output using solid para-H2 within the next few weeks.
Acknowledgments
Benjamin McCall Takamasa Momose Manori Perera Michael Porambo Heather Hanson Preston Buscay Kristin Evans
The McCall Research Group