Thin films of AlN doped with chromium were deposited on flat Si (100) substrates and optical fibers by rf magnetron sputtering, using 100-200 W rf power and 5-8 mTorr nitrogen. The thickness of the films on the flat silicon substrate was 400nm and on optical fibers with 80 μm and smaller diameters was up to 10 μm. Surface characterization and luminescence properties were investigated to fabricate resonant laser cavities. X-ray diffraction and scanning electron microscope studies showed that films deposited on flat silicon were amorphous, while those deposited on the fibers show columnar growth and some gain structure, most probably due to a temperature rise at the substrate during deposition. Cathodoluminescence and photoluminescence of the as-deposited and thermally activated AlN:Cr films showed an emission peak at 702nm as a result of the 4T2 → 4A2 transition. © 2010 Optical Society of America.