Combined optical–infrared single-ion frequency standard

Abstract

A combined infrared-optical frequency-standard scheme has been demonstrated with a single ion of ytterbium. The optical (2)S(1/2)-(2)D(5/2) reference transition at 411 nm and the infrared (2)F(7/2)-(2)D(5/2) 3.43-microm transition were driven sequentially. The structure of the infrared (2)F(7/2)-(2)D(5/2) reference transition at 3.43 microm has also been studied. Infrared transition linewidths of 300 kHz were observed. The output of a Nd:YAG laser and an extended-cavity diode laser were difference-frequency mixed in a crystal of AgGaS(2) to produce narrow-linewidth light at 3.43 microm . Both lasers were frequency stabilized to high-finesse reference cavities.