Infrared studies of single-crystal La_2−xSrxCuO_4−δ and YBa_2Cu_3O_7−δ

Abstract
Polarized infrared reflectance measurements are reported for crystals of La2−xSrxCuO4−δ and YBa2Cu3O7−δ. Free-carrier reflectance is observed in the copper oxide planes, and strong phonons are observed in the perpendicular direction. The interpretation of the infrared optical properties is discussed.