The infrared response of superlattices (SLs) composed of YBa2Cu3O7 (YBCO) and La-0.67 Ca0.33MnO3 (LCMO) on SrTiO3 substrate has been studied by ellipsometry in the range from 400 to 5000 cm(-1). We use a model calculation of the optical response to distinguish the contribution of the SL and the substrate. The infrared data provide an evidence of a strong interaction between the YBCO and LCMO layers. The mid-infrared resonance located at approximately 1000-3000 cm(-1) is discussed in terms of the polaronic absorption in LCMO. The resonance could indicate a charge transfer from the YBCO to the LCMO layers. (C) 2004 Elsevier B.V. All rights reserved.