B C. Young

Sub-dekahertz ultraviolet spectroscopy of 199Hg+

Using a laser that is frequency locked to a Fabry-Perot etalon of high finesse and stability, we probe the 5d(10)6s (2)S(1/2)(F = 0)<-->5d(9)6s(2) (2)D(5/2)(F = 2) Deltam(F) = 0 electric-quadrupole transition of a single laser-cooled 199Hg+ ion stored in a cryogenic radio-frequency ion trap. We observe Fourier-transform limited linewidths as narrow as 6.7 Hz at 282 nm ( 1.06x10(15) Hz), yielding a line Q approximately 1.6x10(14). We perform a preliminary measurement of the 5d(9)6s(2) (2)D(5/2) electric-quadrupole shift due to interaction with the static fields of the trap, and discuss the implications for future trapped-ion optical frequency standards.

Diode-pumped Nd:FAP laser at 1.126 μm: a possible local oscillator for a Hg + optical frequency standard

We report the efficient operation of a continuous-wave, single-frequency, diode-pumped Nd:FAP laser at 1.126 mum. When frequency quadrupled, such a laser might be used as a local oscillator for an optical frequency standard based on the single-photon (2)S(1/2)-(2)D(5/2) electric quadrupole transition of a trapped and laser-cooled (199)Hg(+) ion. Since the frequencies of the atomic transition and the laser are harmonically related, this scheme helps to simplify the measurement of the S-D clock transition frequency by a phase-coherent chain to the cesium primary frequency standard.

Lasers for an optical frequency standard using trapped Hg+ ions

We are developing an optical frequency standard based on the narrow 281.5 nm transition of trapped lg9Hgt ions. A major step toward the completion of this standard is the construction of an isolated high-finesse Fabry-PCrot cavity to stabilize the local oscillator. The cavity system that we have assembled has enabled the creation of an optical frequency source with good short-term stability. Eventually, this frequency source will derive long-term stability from a lock to the Hgt transition. We have recently demonstrated an improved linewidth of 0.6 Hz (40 s averaging time) for a 563 nm dye laser locked to our stable cavity. Additionally, we are developing solid-state laser replacements for gas and dye lasers presently used for driving 194 nm and 281.5 nm Hgt transitions.

High-resolution, high-accuracy spectroscopy of trapped ions

Microwave spectroscopy using trapped and cooled ions can achieve precision and accuracy comparable to the best cesium frequency standards. We discuss standards based on {sup 199}Hg{sup +} ions trapped in linear Paul traps: the Jet Propulsion Laboratory (JPL) standard, which uses up to 10{sup 7} atoms confined near the trap axis, and the recently evaluated NIST standard, which uses approximately ten ions laser cooled and crystalized on the trap axis. We consider future directions in trapped ion frequency standard work, including the use of entangled states for achieving higher precision, and progress on trapped ion optical frequency standards. Finally, we discuss scientific and technical applications of extremely stable frequency standards.

Lasers for a trapped Hg/sup +/ optical frequency standard

We have demonstrated a frequency source at 563 nm with an approximately 6 Hz linewidth for use in an optical frequency standard based on trapped and cooled /sup 199/Hg/sup +/ ions. Additionally, we are developing solid state laser replacements for gas and dye lasers presently used for driving 194 nm and 282 nm /sup 199/Hg/sup +/ transitions.

High-performance trapped Hg/sup +/ frequency standards

We have demonstrated a new frequency standard, accurate to 3.4/spl times/10/sup -15/, based on the 40.5 GHz ground state hyperfine transition in cooled and trapped /sup 199/Hg/sup +/. We are also developing an optical frequency standard based on /sup 199/Hg/sup +/. The spectral width of the 563 nm laser used in this standard is less than 6 Hz.