Characterization of the ``guided light/photonic crystal'' coupling by absorbance

International audienceConsidering luminescent TiO2 films whose surface was imprinted with a 2D square shaped photonic crystal with different pattern depths (from 20 to 61 nm), we demonstrate the possibility to use simple absorption measurements to evaluate the efficiency of light extraction. Absorption spectra of the patterned systems show absorption peaks, evidencing the coupling between the photonic crystal structure and light guided within the film, in good agreement with 2D-RCWA simulations. The deeper the pattern depth, the stronger the coupling between the guided light and the photonic crystal. Using RCWA simulations, we show that it is possible to evaluate the extraction length, characteristic of the efficiency of light extraction, from the absorption spectra, in good agreement with direct measurements reported elsewhere