New Publication: “Stimulated Raman adiabatic passage for improved performance of a cold-atom electron and ion source”

New electron sources using laser-cooled atoms promise breakthrough enhancements in brightness with potential for ultrafast imaging at atomic scales. In these sources the beam current is intrinsically tied to the efficiency of excitation of the cold atoms. Here we present experiments where we use the counter-intuitive STIRAP technique to increase the excitation efficiency and therefore electron current by 60% compared to conventional incoherent methods.

Reference: B. M. Sparkes, D. Murphy, R. J. Taylor, R. W. Speirs, A. J. McCulloch, R. E. Scholten, Physical Review A 94, 023404 (2016) [pdf]

The volume-averaged efficiency as a function of the delay between the two STIRAP laser pulses (negative delay indicates the characteristic “counter-intuitive” pulse sequence). The inset shows the calculated efficiency as a function of integration radius, indicating a peak efficiency of 82%.