Laser cooling of trapped Ca(+) and measurement of the 3(2)D(5/2) state lifetime

Injection locking of a high power ultraviolet laser diode for laser cooling of ytterbium atoms

We developed a high-power laser system at a wavelength of 399 nm for laser cooling of ytterbium atoms with ultraviolet laser diodes. The system is composed of an external cavity laser diode providing frequency stabilized output at a power of 40 mW and another laser diode for amplifying the laser power up to 220 mW by injection locking. The systematic method for optimization of our injection locking can also be applied to high power light sources at any other wavelengths. Our system does not depend on complex nonlinear frequency-doubling and can be made compact, which will be useful for providing light sources for laser cooling experiments including transportable optical lattice clocks.

Direct frequency comb spectroscopy of trapped ions

Direct frequency comb spectroscopy of trapped ions is demonstrated for the first time. It is shown that the 4s ;{2}S_{1/2}-4p ;{2}P_{3/2} transition in calcium ions can be excited directly with a frequency comb laser that is up-converted to 393 nm. Detection of the transition is performed using a shelving scheme to suppress the background signal from nonresonant comb modes. The measured transition frequency of f=761 905 012.7(0.5) MHz presents an improvement in accuracy of more than 2 orders of magnitude.

Sideband-resolved spectroscopy on the 4 2S(1/2)-3 2D(5/2) transition in single calcium ions by use of fundamental waves of diode lasers

The 4 2S(1/2)-3 2D(5/2) electric quadrupole transition in calcium ions, which is expected to be used in calcium-ion optical frequency standards, is spectroscopically investigated with a laser system that uses only fundamental waves of diode lasers as light sources. Four Zeeman components allowed by the selection rules for the electric quadrupole transition are identified. As for one Zeeman component, one large carrier and accompanying smaller first sidebands are observed, which implies that Lamb-Dicke confinement of the ion is achieved. The compact and reliable system for spectroscopy of single calcium ions described is advantageous for realization of practical optical frequency standards.

Laser cooling of calcium ions by use of ultraviolet laser diodes: significant induction of electron-shelving transitions

Calcium ions are laser cooled in a Paul trap by use of a grating-stabilized UV laser diode. Unusual quantum jumps or fluctuations in the fluorescence signal are observed without application of any shelving lasers. It has become clear that such phenomena can be ascribed to shelving transitions induced by background 393-nm spontaneous photons emitted from the laser medium. Shelving transitions are suppressed by use of an interference filter, and the ions are successfully cooled to crystallization temperature with sufficient reproducibility.

Diode-Pumped Nd:FAP Laser at 1.126 microm: 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.

Laser cooling and isotope separation of Cd(+) ions conf ined in a linear Paul trap

Cadmium ions in a natural isotope mixture have been trapped in a linear Paul trap and laser cooled. The fluorescence spectra from all even isotopes, including the (108)Cd(+) isotopes with a natural abundance of 0.89%, were observed. Additionally, we eliminated the heavier isotopes from the trapping region by adjusting the tuning of the laser frequency and by changing the dc voltage applied to the end electrodes.

Tunable 397-nm light source for spectroscopy obtained by frequency doubling of a diode laser

Continuous-wave radiation of 1.8 mW at 397 nm was generated by frequency doubling a 100-mW GaAlAs diode laser in a lithium iodate crystal placed in an external enhancement cavity. The radiation had a narrow linewidth and a continuous frequency-scanning range of 6 GHz. The UV radiation obtained was applied to laser cooling of calcium ions stored in a rf trap.