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Aims. We seek to probe the Galactic bulge IMF starting from microlensingobservations. Methods. We analyse the recent results of the microlensingcampaigns carried out towards the Galactic bulge presented by the EROS, MACHOand OGLE collaborations. In particular, we study the duration distribution ofthe events. We assume a power law initial mass function, $\xi(\mu)\propto\mu^{-\alpha}$, and we study the slope $\alpha$ both in the brown dwarf and inthe main sequence ranges. Moreover, we compare the observed and expectedoptical depth profiles. Results. The values of the mass function slopes arestrongly driven by the observed timescales of the microlensing events. Theanalysis of the MACHO data set gives, for the main sequence stars, $\alpha=1.7\pm 0.5$, compatible with the result we obtain with the EROS and OGLE datasets, and a similar, though less constrained slope for brown dwarfs. The lackof short duration events in both EROS and OGLE data sets, on the other hand,only allows the determination of an \emph{upper} limit in this range of masses,making the overall result less robust. The optical depth analysis gives a verygood agreement between the observed and the expected values, and we show thatthe available data do not allow one to discriminate between different bulgemodels.

Microlensing constraints on the Galactic Bulge Initial Mass Function