S. C. Bell

Laser frequency offset locking using electromagnetically induced transparency

This research was supported under the Discovery funding scheme of the Australian Research Council Project No. DP0557505.

A slow atom source using a collimated effusive oven and a single-layer variable pitch coil Zeeman slower

We describe a simple slow atom source for loading a rubidium magneto-optical trap. The source includes an effusive oven with a long heated collimation tube. Almost all components are standard vacuum parts. The heating elements and thermocouples are external to the vacuum, protecting them from the hostile hot alkali environment and allowing repair without breaking vacuum. The thermal source is followed by a Zeeman slower with a single-layer coil of variable winding pitch. The single-layer design is simple to construct and has low inductance which allows for rapid switching of the magnetic field. The coil pitch was determined by fitting the analytic form of the magnetic field for a variable winding pitch to the desired magnetic field profile required to slow atoms. The measured magnetic field for the constructed coil is in excellent agreement with the desired field. The source produces atoms at 35 m/s with a flux up to 2 x 10(10) cm(-2) s(-1) at 200 degrees C.

Excited-state imaging of cold atoms

We have investigated state-selective diffraction contrast imaging (DCI) of cold 85Rb atoms in the first excited (52P3/2) state. Excited-state DCI requires knowledge of the complex refractive index of the atom cloud, which was calculated numerically using a semi-classical model. The Autler-Townes splitting predicted by the model was verified experimentally, showing excellent agreement. 780 nm lasers were used to cool and excite atoms within a magneto-optical trap, and the atoms were then illuminated by a 776 nm imaging laser. Several excited-state imaging techniques, including blue cascade fluorescence, on-resonance absorption, and DCI have been demonstrated. Initial results show that improved signal-to-noise ratio (SNR) will be required to accurately determine the excited state fraction. We have demonstrated magnetic field gradient compression of the cold atom cloud, and expect that further progress on compression and additional cooling will achieve sufficient diffraction contrast for quantitative state-selective imaging.

Atomic absorption frequency reference bandwidth limit

We show that the bandwidth for a conventional atomic vapour absorption frequency reference is limited by the atomic lifetime, and propose higher bandwidth frequency discrimination using atomic coherence mechanisms.

Diffraction-contrast imaging of excited-state cold atoms

We have demonstrated off-resonant imaging of a cold atom cloud, computationally extracting the atomic column density map from a diffraction pattern. We are developing the technique to imaging of excited-state atoms.