A YAG/Yb∶YAG/YAG ceramic planar waveguide is manufactured using tape casting combined with vacuum sintering and hot isostatic pressing, which is taken as the laser gain medium to investigate the characteristics of laser amplification. A 1030 nm polarization-maintained (PM) fiber laser is used as the seed laser and a 940-nm diode laser array is used as the pumping source of the amplifier. The pumping light is coupled with the planar waveguide from the end facets. Subsequently, the amplification performances under front-end-pumping and back-end-pumping are compared, and the amplification performances of dual-end pumping are experimentally tested. In case of dual-end pumping, when the seed laser power is 136 W, the laser output power is observed to be 1.41 kW and the slope efficiency is up to 41%. To the best of our knowledge, this is the superior output power worldwide for a laser with this type of ceramic planar waveguide.