The interaction of ultra-short pulses (120 fs) of laser radiation (800 nm) with Si and SiGe samples was analyzed. Some kinds of low-dimensional structures were found. An ablation model was proposed to explain the effect. It has been noticed that a grating shape in 400 nm period scale occurs on surface of silicon. It is found that the grating of one-dimensional structure has an intensive photoluminescene (PL) whose peak is at wavelength 719 nm. The PL peak is smaller, and its mechanism is analyzed from the pulse width and repetitive rate of laser. When the irradiation energy on silicon increases to exceed the ablation threshold for the grating shape to be broken and a kind of sharp conical structure begins to set up. Controlling preparing condition, a high-quality nano-grating can be made on silicon base for diffracting and micro-splitting of beam.