Zhao Quanzhong

Fabrication of Microstructures in LiF Crystals by a Femtosecond Laser

We report the space-selective formation of colour centres and refractive index change in LiF crystals at room temperature by an 800 nm Ti:sapphire femtosecond laser irradiation. Optical absorption and photoluminescence spectra have been measured for the crystal before and after the laser irradiation. The absorption spectra indicate F and F3+ colour centres are induced in LiF after the laser irradiation. When the temperature of heat treatment reaches 300°C, the absorption peak disappears, indicating that the induced colour centres are bleached. The induced refractive index change is also evaluated. A mechanism for the formation of colour centres and refractive index change is proposed.

Formation of arrayed holes on metal foil and metal film by multibeam interfering femtosecond laser beams

We report on an optical interference method to fabricate arrayed holes on metal nickel foil and aluminum film deposited on glass substrate by means of five-beam interference of femtosecond laser pulses. Optical microscope and scanning electron microscope observations revealed that arrayed holes of micrometre-order were fabricated on both metal foil and metal film. The present technique allows one-step, large-area, micrometric processing of metal materials for potential industrial applications.

Self-organized voids revisited: Experimental verification of the formation mechanism

In this paper, several experiments were conducted to further clarify the formation mechanism of self organized void array induced by a single laser beam, including energy-related experiments, refractive-index-contrast-related experiments, depth-related experiments and effective-numerical-aperture experiment. These experiments indicate that the interface spherical aberration is indeed responsible for the formation of void arrays.