[en] The CLAS collaboration has recently completed first measurements of the double polarization observables C_x and C_z for the reactions K⁺ Lambda and K⁺ Sigma^o photoproduction. C_x and C_z are the beam-recoil polarization asymmetries measuring the polarization transfer from incoming circularly polarized photons to the outgoing hyperons along two directions in the reaction's production plane. The Lambda is found to be nearly maximally polarized along the direction of the incident photon's polarization for forward-going kaons. Polarization transfer to the Sigma^o is different from the Lambda case