All-diode-laser optical frequency standard based on laser-trapped Ca atoms

We describe a high performance optical frequency standard at 657 nm based on laser-trapped Ca. Using two semiconductor laser systems (423 nm for trapping and 657 nm for spectroscopy), we have been able to obtain sub-kilohertz optical linewidths and a relative Allan variance of 1.3×10^-14 at one second, with prospects for considerable improvement. This Ca standard can be used to make a phase-coherent frequency measurement of the 282 nm ¹⁹⁹Hg⁺ optical standard