Sung Jong Park

Absolute frequency measurement of 1S0(F = 1/2)–3P0(F = 1/2) transition of 171Yb atoms in a one-dimensional optical lattice at KRISS

We measured the absolute frequency of the optical clock transition 1S0 (F = 1/2) - 3P0 (F = 1/2) of 171Yb atoms confined in a one-dimensional optical lattice and it was determined to be 518 295 836 590 863.5(8.1) Hz. The frequency was measured against Terrestrial Time (TT; the SI second on the geoid) by using an optical frequency comb of which the frequency was phase-locked to an H-maser as a flywheel oscillator traceable to TT. The magic wavelength was also measured as 394 798.48(79) GHz. The results are in good agreement with two previous measurements of other institutes within the specified uncertainty of this work.

Laser-induced birefringence in a wavelength-mismatched cascade system of inhomogeneously broadened Yb atoms

We report the observation of laser-induced birefringence (LIB) in a wavelength-mismatched cascade system (J=0{r_reversible}J=1{r_reversible}J=0 transitions) of inhomogeneously broadened ytterbium atoms with strong pump and probe fields. We investigate the transmission spectrum of two circular polarization ({sigma}{sub p}{sup +} and {sigma}{sub p}{sup -}) components of strong probe field at fixed frequency, depending on the detuning of a circularly polarized ({sigma}{sub c}{sup -}) coupling field from two-photon resonance. We find that the {sigma}{sub p}{sup +} ({sigma}{sub p}{sup -}) polarized component exhibits a narrow electromagnetically induced absorption (transparency) spectrum. Numerical solutions of density matrix equations show qualitative agreement with experimental results. A Doppler-free dispersive LIB signal is obtained by detecting the Stokes parameter of the probe field, enabling us to stabilize the frequency of the coupling laser without frequency modulation.

Development of a /sup 171/Yb/sup +/ microwave frequency standard at the National Measurement Institute, Australia

Microwave frequency standards based on the 12.6 GHz ground state hyperfine transition in 171Yb+ have been under development at the National Measurement Institute, Australia, for many years. Using a laser-cooled ion cloud, the transition frequency was measured in 2001 to an accuracy of 8 parts in 1014, limited by the homogeneity of the magnetic field due to the stainless-steel vacuum chamber. We have designed and commissioned a new chamber in the alloy CrCu, which is non-magnetic and has good vacuum properties. The design incorporates large viewports and high-quality quartz windows for optical access. Uncertainties associated with field inhomogeneity in the new vacuum system are now below 1 part in 1015, a significant reduction which permits operation in the 10-15 accuracy range. We have also demonstrated the use of photoionization to load the trap in a preliminary experiment, including isotope-selective loading

171Yb+ Microwave Frequency Standard

Microwave frequency standards based on the 12.6 GHz ground state hyperfine transition in 171Yb+ have been under development at the National Measurement Institute, Australia, for many years. Using a laser-cooled ion cloud, the transition frequency was measured in 2001 to an accuracy of 8 parts in 1014 , limited by the homogeneity of the magnetic field. Uncertainties associated with field inhomogeneity in the new vacuum system are now below 1 part in 1015. We demonstrate that other systematic uncertainties such as AC Zeeman shift, microwave imperfections and pressure shifts permit operation in the 10-15 accuracy range. The performance of the 171Yb+ microwave standard can therefore be comparable to that of a caesium fountain.

Effects of Coherent Uncoupled Excited States on Electromagnetically Induced Transparency

We report on the effects of coherent uncoupled excited states on the electromagnetically induced transparency exhibited in the absorption spectrum of a cold atomic sample stored in a magnetooptical trap (MOT). The absorption spectrum of a weak laser field reveals a three peaked spectral profile, consisting of the two Autler–Townes peaks and an uncoupled absorption peak. The spectrum is explained by calculations based on the density-matrix equations which take into account all 13 Zeeman sublevels in the degenerate Λ system.