Light and heat driven precipitation of copper nanoparticles inside Cu²⁺-doped borate glasses

We report on highly localized precipitation of copper nanoparticles in borate glasses by irradiation with femtosecond laser pulses. The area in the vicinity of the laser focal point of an 800 nm femtosecond laser inside the glass sample became red due to the precipitation of copper nanoparticles after the femtosecond laser irradiation. The precipitation of copper nanoparticles was confirmed by transmission electron microscopy images, electron energy-loss spectra and absorption spectra. The average power of the femtosecond laser and the irradiation time are two important factors related to the formation of the precipitates. The mechanism of the precipitation of copper nanoparticles is discussed.