Heating rates in a thin ion trap for microcavity experiments

We have built and characterized a novel linear ion trap. Its small horizontal electrode separation of 250um would previously have required microfabrication methods, while our trap was machined conventionally. The thin trap is designed to accommodate a transverse optical cavity of 0.5mm length, a requirement for cavity-QED experiments with trapped ions in the strong coupling regime. The sandwich structure of the electrodes allows for a very accurate alignment. Employing the Doppler-recooling method, we found that intermittent laser-induced radiation pressure has a significant effect on the ion's spectrum. This must be taken into account to correctly determine the heating rate of the trap. To this end, we have derived an analytic expression for the spectral line shape of the ion, which includes the effect of natural line broadening, heating as well as radiation pressure. We apply it to determine the accurate heating rate of the system.