High stability optical frequency reference based on thermal calcium atoms.

摘要

Here we report an imprecision below 10-14 with a simple, compact optical frequency standard based upon thermal calcium atoms. Using a Ramsey-Bord spectrometer we excite features with linewidths less than 5 kHz for the 1S0-3P1 intercombination line at 657 nm. We have measured a fractional frequency instability below 6 x 10-15 at 1 s, with good prospects for still quieter performance. The key remaining issue for this standard is how well first- and secondorder Doppler drifts can be suppressed. Due to its experimental simplicity such a system could find application as a less accurate, but high stability reference for commercial applications.