Ultra-high vacuum compatible full metal atom beam shutter for optical lattice clocks.

We developed a shutter driven by a solenoid to switch on/off the atomic beam of optical lattice clocks developed at KRISS [C. Y. Park et al., Metrologia 50, 119 (2013), S. Lee et al., New J. Phys. 18, 033030 (2016), H. Kim et al., Jpn. J. Appl. Phys. 56, 050302 (2017), and H. Kim et al., Metrologia 58, 055007 (2021)]. The shutter design was focused on long lifetime and compatibility with an ultra-high vacuum (UHV) environment. Thus, the solenoid was designed to be easily installed and removed from the air-side of a CF flange of the shutter. The flag in the vacuum-side moves only with the simple spring action of a sheet of a metal plate without any frictional movement of mechanical parts. All parts in the vacuum-side were made of metals (stainless steel and pure iron) to be baked over the temperature of 200 °C for UHV. The flag head of the shutter displaces up to 10 mm (5 mm) with a response time of 50 (30 ms) and 80 ms (10 ms) for the opening-action and the closing-action, respectively. The lifetime was tested up to 6 × 106 cycles with no performance degradation. We expect the actual lifetime to be much longer than this by virtue of its friction-free design.

Robust frequency stabilization and linewidth narrowing of a laser with large intermittent frequency jumps using an optical cavity and an atomic beam.

An experimental method is developed for robust frequency stabilization using a high-finesse cavity when the laser exhibits large intermittent frequency jumps. This is accomplished by applying an additional slow feedback signal from Doppler-free fluorescence spectroscopy in an atomic beam with increased frequency locking range. As a result, a stable and narrow-linewidth 556 nm laser maintains the frequency lock status for more than a week and contributes to more accurate evaluation of the Yb optical lattice clock. In addition, the reference optical cavity is supported at vibration-insensitive points without any vibration isolation table, making the laser setup more simple and compact.

Advanced Satellite-Based Frequency Transfer at the 10-16 Level.

Advanced satellite-based frequency transfers by two-way carrier-phase (TWCP) and integer precise point positioning have been performed between the National Institute of Information and Communications Technology and Korea Research Institute of Standards and Science. We confirm that the disagreement between them is less than at an averaging time of several days. In addition, an overseas frequency ratio measurement of Sr and Yb optical lattice clocks was directly performed by TWCP. We achieved an uncertainty at the mid-10-16 level after a total measurement time of 12 h. The frequency ratio was consistent with the recently reported values within the uncertainty.

Atom shutter using bender piezoactuator.

A flag-type atom shutter based on a rotating lever that is driven by a bender piezoelectric actuator was developed to manipulate atomic beams. The shutter flag was displaced by ∼10 mm to open and close a 5-mm-diameter aperture with a shutter time of 13 ms that produced small mechanical vibrations. The short-term shutter time stability for each cycle was 0.03 ms and the long-term stability over an average of 20 000 cycles was 0.02 ms. The operational cycle number (lifetime) of the shutter reached 2.0 × 106 cycles after an intermittent operation over a period of eight months in an ultra-high vacuum chamber, and another shutter in an atmospheric environment swung for 2.6 × 107 cycles of continuous operation at 5 Hz for a period of 60 days without major problems. The shutter was shown to be compatible with the operation in an ultra-high vacuum at a low 10-7 Pa level after a gentle baking treatment.

Magic polarization for optical trapping of atoms without Stark-induced dephasing.

We demonstrate that the differential ac-Stark shift of a Zeeman-sensitive ground hyperfine transition in an optical trap can be eliminated by using properly polarized trapping light. We use the vector polarizability of an alkali-metal atom to produce a polarization-dependent ac-Stark shift that resembles a Zeeman shift. We study a transition from the |2S1/2,F=2,mF=-2> to the |2S1/2,F=1,mF=-1> state of 7Li to observe 0.59±0.02 Hz linewidth with interrogation time of 2 s and 0.82±0.06 s coherence time of a superposition state. Implications of the narrow linewidth and the long coherence time for precision spectroscopy and quantum information processing using atoms in an optical lattice are discussed.