Fabrication of Ruby thin film for temperature indicator application

Chromium doped sapphire (Ruby) films have been fabricated on Si substrate by laser ablation, and their fundamental optical property and thermal characteristics are evaluated for temperature sensor application. The red emission near 700 nm which originates from 3d transition in Cr³⁺ ions was clearly observed from the Ruby films. The split of PL peak, originated in 3d-orbital of chromium ion, is also clearly observed from Ruby films. Temperature dependence of PL spectrum from ruby films was measured under Ar laser excitation. PL intensity and PL peak position greatly vary with temperature ranging from 293 K to 443 K. To take the advantage of this phenomenon, the temperature sensor with calibration free can be developed.