Abstract
The authors report on a thermal beam optical frequency reference with a fractional frequency instability of 9.2×10−14 at 1 s reducing to 2.0×10−14 at 64 s before slowly rising. The 1S0↔3P1 intercombination line in neutral 40Ca is used as a frequency discriminator. A diode laser at 423 nm probes the ground state population after a Ramsey–Bordé sequence of 657 nm light-field interactions on the atoms. The measured fractional frequency instability is an order of magnitude improvement on previously reported thermal beam optical clocks. The photon shot-noise of the read-out produces a limiting square root Λ-variance of 7×10−14/.
Original language | English |
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Pages (from-to) | Article number 031103, 3pp |
Journal | Applied Physics Letters |
Volume | 95 |
Issue number | 3 |
DOIs | |
Publication status | Published - 2009 |