Interplay between wave packet interferences and second harmonic generation

Wavepacket interferences have been performed in the (4s-5p) transition of a tomic potassium using two different schemes to prepare the two-pulse sequen ce used to excite the atom. In the first case, the pulses at 810 nm are fir st frequency doubled and then split within a Michelson interferometer. In t he second case, the pulses are first split and then frequency doubled. Alth ough these schemes share some similarities, differences appear in case of t otal or partial overlap between the pulses. These differences are discussed and the second scheme is shown to be strictly equivalent to previous exper iments realised in caesium where a two-photon absorption replaces the doubl ing crystal followed by a one-photon absorption. (C) 2000 Elsevier Science B.V. All rights reserved.