Tai Hyun Yoon

Sub-Doppler molecular-iodine transitions near the dissociation limit (523-498 nm).

A widely tunable and high-resolution spectrometer based on a frequency-doubled Ti:sapphire laser was used to explore sub-Doppler transitions of iodine molecules in the wavelength range 523-498 nm. The wavelength dependence of the hyperfine transition linewidth of iodine was mapped out in this region, and the narrowest linewidth was ~4 kHz near 508 nm. The hyperfine-resolved patterns were found to be largely modified toward the dissociation limit. The observed excellent signal-to-noise ratio should lead to high-quality optical frequency standards that are better than those of the popular 532-nm system.

Efficient magneto-optical trapping of Yb atoms with a violet laser diode

We report an efficient trapping of rare-earth-metal Yb atoms with a high-power violet laser diode (LD). An injection-locked violet LD with a 25-mW frequency-stabilized output was used for the magneto-optical trapping (MOT) of fermionic as well as bosonic Yb isotopes. A typical number of 4×10 6 atoms for 1 7 4 Yb with a trap density of ∼ 1×10 8 cm - 3 was obtained. A 10-mW violet external-cavity LD was used for the one-dimensional slowing of an effusive Yb atomic beam without a Zeeman slower resulting in a 35-fold increase in the number of trapped atoms. The overall characteristics of our compact violet MOT, e.g., the loss time of 1 s, the loading time of 400 ms, and the cloud temperature of 0.7 mK, are comparable to those in previously reported violet Yb MOTs, yet with a greatly reduced cost and complexity of the experiment.

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.

High-resolution Rb two-photon spectroscopy with ultrafast lasers

A two-photon transition in cold Rb atoms will be probed with a phase-coherent wide-bandwidth femtosecond laser comb. Frequency domain analysis yields a high resolution picture where phase coherence among various transition pathways through different intermediate states produces interference effects on the resonantly-enhanced transition probability. This result is supported by the time domain Ramsey interference effect. The two-photon transition spectrum is analyzed in terms of the pulse repetition rate and carrier frequency offset, leading to a cold-atom-based frequency stabilization scheme for both degrees of freedom of the femtosecond laser.