Line-center stabilized CO2 lasers as secondary frequency standards - Determination of pressure shifts and other errors
Abstract
The 4.3 micron CO2 fluorescence stabilization method is reviewed and a two-channel heterodyne system with a fractional frequency stability of less than 2 x 10 to the -12th is described. Frequency reproducibility and causes of frequency shifts and errors in the saturation resonance are discussed. A new technique is employed to eliminate frequency offset errors caused by the nonzero slope of the power versus frequency characteristics of the lasers over the frequency range of the nonlinear resonance dip. Pressure shifts of the standing wave saturated resonance have been measured in the 9 and 10 micron P and R lasing transitions of CO2. At low pressures, the measured shifts for four different isotopes are all blue, instead of red as predicted by semiclassical theory. Measurements at higher pressures reveal red shifts. Perturber gas data show blue shifts for heavier perturber atoms or molecules, red shifts for He and H2.
- Publication:
-
IEEE Journal of Quantum Electronics
- Pub Date:
- August 1985
- DOI:
- 10.1109/JQE.1985.1072806
- Bibcode:
- 1985IJQE...21.1159S
- Keywords:
-
- Carbon Dioxide Lasers;
- Fluorescence;
- Frequency Shift;
- Frequency Standards;
- Laser Stability;
- Doppler Effect;
- Heterodyning;
- Isotopes;
- Signal To Noise Ratios;
- Wave Propagation;
- Lasers and Masers