Thomas Lindvall

Trapping atoms on a transparent permanent-magnet atom chip

We describe experiments on the trapping of atoms in microscopic magneto-optical traps on an optically transparent permanent-magnet atom chip. The chip is made of magnetically hard ferrite-garnet material deposited on a dielectric substrate. The confining magnetic fields are produced by miniature magnetized patterns recorded in the film by magneto-optical techniques. We trap Rb atoms on these structures by applying three crossed pairs of counterpropagating laser beams in the conventional magneto-optical trapping geometry. We demonstrate the flexibility of the concept in creation and in situ modification of the trapping geometries through several experiments.

Effect of optical pumping on alkali-atom Doppler-limited spectra

Using a three-level model and semiclassical density matrix formalism, we show that optical pumping influences both line positions and amplitudes in Doppler-broadened alkali-atom D1 and D2 spectra for intensities much lower than the two-level atom saturation intensity. The influence on the D2 spectrum is particularly interesting due to the presence of closed hyperfine transitions unaffected by optical pumping. This effect is of importance for example when lasers are frequency stabilized using linear absorption or when the alkali-atom vapour pressure is determined using absorption measurements.

All-optical atomic clock based on dark states of 85Rb

An all-optical RF standard based on dark states of 85Rb atoms has been developed. With this system we were able to measure ultra-narrow optically induced hyperfine dark resonances below 20Hz (Q-value > 1.5 × 108). The frequency of a signal generator was stabilized to the dark resonance giving a relative frequency stability (square root of Allan variance) of 3.5 × 10−11τ−1/2 (1 s < t < 2000 s). The best stability reached at an integration time of t = 2000 s was 6.4 × 10−13, which is sufficient for many high-precision applications. The frequency shifts caused by various experimental parameters were also studied.