The effect of material surface morphology on the periodic subwavelength of nano-structures induced by a femtosecond (fs) laser was investigated systematically from the initial surface roughness, the different scratches, the pre-formed ripples, and the “layer-carving” technology experiments. The results of the comparative experiments indicate that the initial surface conditions of the target surface have no obvious effects on the spatial structured periods (SSPs) and the ripple orientation of the periodic nano-structures induced by a fs laser, which agreed well with the foretold present surface two-plasmon resonance (STPR) model. Furthermore, different shapes of nano-grids with high regularity and uniformity were obtained by fs-laser fabrication.

We demonstrate a continuous-wave (CW) dual-wavelength Nd:YVO4 laser working at 1064 and 1066 nm simultaneously. The method of Nd:YVO4 crystal angle tuning is used to balance the ratio of the stimulated emission cross sections of the two wavelengths, leading to the realization of a simultaneous dual-wavelength operation from only one laser. The experimental results show that at a 2.85 W pump power, the maximum output powers at wavelengths of 1064 and 1066 nm are 0.55 and 0.54 W, respectively. The linear resonate cavity is as short as 10 mm, which gives the laser the advantages of a miniature configuration and low threshold. Such a dual-wavelength laser can be very attractive for the development of compact THz sources based on difference frequency generation.

The self-formation of periodic subwavelength ripples by linear polarized femtosecond laser scanning planar and non-planar tungsten targets on the employed laser wavelength, scanning speed, and energy fluence are examined systematically. The results show that, for a certain laser wavelength, the scanning conditions have no obvious effect to the morphological features of grating structures in the threshold range of laser fluence. The spatial structured period of gratings can be self-consistently interpreted by recently presented physical model of surface two-plasmon resonance. The subwavelength structures on cylindrical surface would be a good method to realize unique surface functions on complex surface of micro-devices.

The films of few-layer graphene are formed through laser exfoliation of a highly ordered pyrolytic graphite (HOPG), without a catalytic layer for the growth process. The femtosecond (fs) laser exfoliation process is investigated at different laser fluences and substrate temperature. For fs laser exfoliation of HOPG, the few-layer graphene is obtained at 473 K under an optimal laser fluence. The formation of few-layer graphene is explained by removal of intact graphite sheets occurred by an optimal laser fluence ablation. The new insights may facilitate the controllable synthesis of large area few-layer graphene.

The periodic ripple structures on wolfram and titanium surfaces are induced experimentally by linear polarized femtosecond laser pulses at small incident angles. The structural features show a material difference in the s- and p-polarized laser irradiation. The interspace between the ripples increases significantly for p-polarized laser irradiation when it exceeds a threshold angle, and the ripples’ periodicities are larger than the wavelength of the incident p-polarized femtosecond laser; however, no significant change in the period of the ripples is observed with increasing incident angle for s-polarized laser irradiation. To explain these phenomena we propose a resonant absorption mechanism, by which the experimental observations can be interpreted.