Nanostructure induced by femtosecond laser in Various OH-contents silicas

Synthetic fused silicas with different OH content were irradiated with an ultrashort pulse laser, and the induced nanostructures were investigated. Compared with the samples before laser irradiation, two absorption bands centered at 4.8 eV corresponding to the E' (alphaSi*) center and at 5.8 eV corresponding to the non-bridging oxygen hole center (NBOHC, alphaSi-O*), were observed after laser irradiation in high-OH silicas. A photoluminescence band with photon energy of 1.9 eV was observed in the irradiated silicas under 4.8 eV light excitation. Though no red photoluminescence was observed after irradiating the inside of the low OH-containing silica samples, a similar phenomenon occurred when the laser beam was focused near the surface of low-OH silicas. The induced structures relaxed after annealing at 400 degrees C. A possible model for the generation of 1.9 eV photoluminescence induced by an ultrashort pulse laser in wet and dry silicas was proposed.