Alfa-NaYF4:18%Yb,0.2%Er nanocrystals have been synthesized. The average size of nanocrystals is 15 nm. The fluorescence spectra of the nanocrystals excited under 980 nm LD was recorded. An optical waveguide amplifier was fabricated using SU-8 2005 polymer doped with 0.21 wt% of nanocrytals. For an input signal power of 0.05 mW and a pump power of 212 mW, a relative optical gain of 3.3 dB at 1520 nm was achieved.