Optical amplification enhancement in photonic crystals

Improving and controlling the efficiency of a gain medium is one of the most challenging problems of laser research. By measuring the gain length in an opal-based photonic crystal doped with laser dye, we demonstrate that optical amplification is more than twenty-fold enhanced along the Γ-K symmetry directions of the face-centered-cubic photonic crystal. These results are theoretically explained by directional variations of the density of states, providing a quantitative connection between density of the states and light amplification.