Factors that contribute to the temperature dependence of a resonant frequency in a low-expansion optical cavity are
discussed, including deformation at the cavity ends due to different coefficients of thermal expansion (CTE) of the
spacer, optically-contacted mirror substrate and coating. A model of the temperature dependence is presented that
incorporates finite-element-analysis of the cavity ends. A measurement of frequency versus temperature of a cavity
mode is used along with the model to deduce a spacer's CTE versus temperature profile. The measured profile
correlates very well with a separate experiment utilizing a temporary surface-mounted Fabry-Perot cavity fabricated on
the outside of the spacer with hydroxy-catalysis bonding.
New scientific insight and technological developments of the past few years have stimulated renewed enthusiasm for the development of optical frequency standards. Long-standing problems have now been eliminated, and it appears that frequency standards using stable lasers and optical transitions may someday replace modern atomic clocks that are based on microwave transitions.
We demonstrate a high sensitivity detection in the weak magnetic-dipole band of molecular oxygen near 764 nm, using a high-finesse Fabry-Perot cavity to provide an equivalent path length of 980 meters.
To measure trace concentrations of the atmospheric radical NO3 we are investigating the use of two amplitude stabilized diode lasers, one tunes to the center of the absorption profile, and the second tuned to a wavelength outside the absorption. This approach is taken because the absorption feature is much broader than the visible diode laser's tuning range and removing the sample concentration from the beam path to measure the baseline is difficult. This paper describes the preliminary system design, interferences expected from water, and electronics design.
A diode laser spectrometer in the visible range was developed. To achieve narrow linewidth and high power, a master-laser/slave system was employed. High-resolution spectroscopy of the 1S0-3P1 transition of Ca was performed and optical Ramsey fringes were observed with a resolution of below 36 lHz using a thermal atomic beam.
The increase low-frequency amplitude noise on several extended cavity diode lasers was measured when frequency of phase lock servos were applied using the injection current as the feedback channel. The AM noise increase inside the FM servo bandwidth is approximately that expected from the suppression of frequency noise uncorrelated with the inherent amplitude noise of the laser.
Heterodyne methods have been used in conjunction with molecular calculations to accurately determine the wavelengths of more than 35,000 infrared transitions. We have used high speed whisker contract Schottky diodes to extend this technology to the 0.8 micrometers spectral region. Using microwave harmonic mixing we demonstrate that it is possible to detect beat notes between diode lasers to frequencies as high as 400 GHz.
Linewidth reduction of an extended cavity diode laser at 657 nm was accomplished by negative feedback to an intra-cavity ADP crystal. High resolution (170 kHz wide) saturated absorption signals were recorded of the calcium intercombination line which is of interest for a frequency standard. The spectrum of the red 62p3/2 - 92s1/2 cesium line in a magneto-optical cell trap was also investigated.
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