Structural phase transition as a mechanism for broadband, low-threshold reflectivity switching in gallium

We report that a nanoscale laser-induced structural phase transition involving just a few nanometers of gallium at an interface with silica can drive reversible changes in the optical properties of the interface in a very broad spectral range from 440 to 680 nm and beyond. At temperatures up to 15° below the melting point of gallium (30 °C) 3 ns excitation pulses, with fluences of just a few mJ/cm2, are sufficient to induce reflectivity increases of up to 40%.