The LaPO4:Er,Yb nanocrystals of average particle size about 5-7 nm were prepared from solution-based reaction. The nanocrystals were successfully incorporated into the sol-gel organic/inorganic hybrid matrix up to 30 wt.% without phase separation. The nanocomposite films showed strong luminescence intensity in the near infrared region around 1550 nm after heat treatment below 150 degrees C. The refractive indices of the composite films were adjustable by controlling both the Zr/Si ratio in the sol-gel hybrid matrices and the contents of the LaPO4:Er,Yb nanocrystals incorporated in the matrices. The propagation loss of the composite films was about 0.5 dB/cm, and that was prone to be increased with increasing the contents of the LaPO4:Er,Yb nanocrystals. (c) 2005 Elsevier B.V. All rights reserved