Ultrafast Optical Hydrogen Modulator in a Palladium Hydride Nanoparticulate Thin Film

Electro- and thermochromic materials change their optical properties through the physical movement of atomic species within thin films. This movement is induced by electric fields or high temperatures and occurs on the second to minute timescale. Ultrashort laser pulses can manipulate atomic positions on the femto- to picosecond timescale. In this work, we modulated the optical properties of a palladium hydride nanoparticulate thin film on the picosecond timescale using femtosecond optical pulses. Density functional theory calculations confirmed that the incident photons activate interstitial hydrogen atoms and the subsequent trajectories of these atoms affect the dielectric properties of the palladium hydride thin film. These responsive interstitial hydrogen atoms provide a modulator for optical switching on the picosecond timescale and could lead to faster photochromic materials.