near-ir extended cavity diode laser for methane spectroscopy · •optical reference for...
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Near-IR Extended Cavity Diode Laser for Methane Spectroscopy
David Mayrhofer, University of RochesterDr. Brian Washburn, Kansas State University
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Why do we want to look at methane?
• Destructive Greenhouse Gas• Important Agricultural Gas• Optical Reference for Telecommunications in the near-infrared (1600 nm)
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Left: From “Gas Sensor Based on Photonic Crystal Fibres in the 2ν3and ν2 + 2ν3 Vibrational Bands of Methane” by Ana M. Cubillas, Jose M. Lazaro, Olga M. Conde, Marco N. Petrovich, and Jose M. Lopez-Higuera
Top Right: http://www2.ess.ucla.edu/~schauble/MoleculeHTML/CH4_html/CH4_page.html
Bottom Right: Data from From “Methane spectroscopy in the near infrared and its implication on atmospheric retrievals” by C. Frankenberg, T. Warneke, A. Butz, I. Aben, F. Hase, et al.
Spherical Top Molecule
Methane Spectroscopy
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Methane Line Width
Left: From Spectral Calculator
For a 1 meter fiber at 10 torr
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Extended Cavity Diode Laser
• Narrow Bandwidth (< 1 MHz)
• Stable and Tunable Frequency (Over 7.5 GHz)
• Cost Effective
http://optics.ph.unimelb.edu.au/atomopt/publications/littrow_rsi_vol72_p4477_2001.pdf
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Position of Grating
Left: https://commons.wikimedia.org/w/index.php?curid=21807350Right: Design by Ottilia Ni
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Position of Grating
Left: https://commons.wikimedia.org/w/index.php?curid=21807350Right: Design by Ottilia Ni
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Free Spectral Range
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Initial Design• Cooling system fails at
currents above 500 mA
Peltier Cooler
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Cooling System Changes
• Much Larger Peltier Cooler• Replaced Ring With Block• Diode held in place with a
thin aluminum sheet• Unable to fit the original
grating/mirror mount in setup
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Grating/Mirror Mount
Grating Mirror
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Fully Assembled Mount
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Current Design
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Current Design
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Line Width With No Feedback
750 mA
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Line Width With Feedback
1A
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Future work and Summary• Successfully created stable cooling design and mount for the grating to narrow line width
• Continue to work with line width
• Measure tunability of laser
• Measure absorption of methane