RESUMO
This erratum corrects an error in Appl. Opt.62, 3932 (2023)APOPAI0003-693510.1364/AO.488653. The correction does not affect the results and conclusions of the original paper.
RESUMO
We have carried absolute frequency measurements of the (6s 2) 1 S 0-(6s6p) 3 P 1 transition in 171 Y b (intercombination line), where the spin-1/2 isotope yields two hyperfine lines. The measurements rely on sub-Doppler spectroscopy to yield a discriminator to which a 556 nm laser is locked. The frequency reference for the optical frequency measurements is a high-quality quartz oscillator steered to the GNSS time scale that is bridged with a frequency comb. The reference is validated to â¼3×10-12 by spectroscopy on the 1 S 0- 3 P 0 (clock) line in laser cooled and trapped 171 Y b atoms. From the hyperfine separation between the F=1/2 and F=3/2 levels of 3 P 1, we determine the hyperfine constant to be A(3 P 1)=3957833(28)k H z.
RESUMO
The most common time-domain measure frequency stability, the Allan variance, is typically estimated using a frequency counter. Close examination the operation of modern high-resolution frequency counters shows that they do not make measurements in the commonly assumed. The consequence is that the results typically reported by many laboratories using these counters are not, in fact, the Allan variance, but a distorted representation. We elucidate the action of these counters by consideration of their operation in the Fourier domain, and demonstrate that the difference between the actual Allan variance and that delivered by these counters can very significant for some types of oscillators. We also discuss ways to avoid, or account for, a distorted estimation of Allan variance.
RESUMO
We discuss various aspects of high resolution measurements of phase fluctuations at microwave frequencies. This includes methods to achieve thermal noise limited sensitivity, along with the improved immunity to oscillator amplitude noise. A few prototype measurement systems were developed to measure phase fluctuations of microwave signals extracted from the optical pulse trains generated by femtosecond lasers. This enabled first reliable measurements of the excess phase noise associated with optical-to-microwave frequency division. The spectral density of the excess phase noise was found to be -140 dBc/Hz at 100 Hz offset from the 10 GHz carrier which was almost 40 dB better than that of a high quality microwave synthesizer.