Mainz 2017 – scientific programme
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A: Fachverband Atomphysik
A 24: Laser Development and Applications (Spectroscopy) (with Q)
A 24.8: Talk
Wednesday, March 8, 2017, 16:15–16:30, P 5
Towards Precision Infrared Spectroscopy on Small Molecules — •Arthur Fast1, John E. Furneaux2, and Samuel A. Meek1 — 1Max Planck Institute for Biophysical Chemistry, Germany — 2University of Oklahoma, USA
Our goal is a high resolution measurement of the two-photon v = 2 ← v = 0 vibrational transitions in the hydroxyl (OH) radical with a relative accuracy of 10−14. These transitions can be used for a test of a possible time variation of the electron-proton mass ratio. The core of this endeavor is a laser beam in the mid infrared region at 2.9 µm with a narrow optical linewidth below 1 kHz. This is the idler wavelength of an optical parametric oscillator (OPO) pumped at 1064 nm by a Nd:YAG laser. The same laser is also frequency-doubled and locked to a molecular iodine transition at 532 nm. By doing this, the Nd:YAG laser obtains a high short term stability, around 10−14 at the one-second timescale. To transfer this stability to the idler wavelength of the OPO at 2.9 µm we make use of an optical frequency comb. The frequency comb is stabilized to the Nd:YAG laser, and the OPO is stabilized to the frequency comb by controlling its cavity length with a piezo mirror. The frequency comb is also used to compare the measured absolute frequencies of the various lasers to a GPS-linked radio frequency reference. In this way, we obtain a long-term stability and absolute accuracy for our spectroscopic measurements.