A composite waveguide was fabricated by dispensing polymer on top of an erbium/ytterbium codoped bulk glass. The parabolic surface of the polymer layer induces a transverse graded index waveguide behavior enabling tighter lateral confinement of light than in a typical step-index multimode waveguide. Spontaneous emission of light in the 1520-1570-nm band has been observed, We have also observed up to 1.7-dB enhancement of transmitted signal with 210 mW of launched 975-nm pump light in a waveguide 1.0-cm long.