Cao Shi-Ying

Ti:sapphire femtosecond comb with two spectral broadening parts

The first generation of femtosecond optical frequency comb (FOFC) based on the Ti:sapphire femtosecond laser in National Institute of Metrology of China, is improved and optimized in this paper. By changing the repetition rate of the femtosecond laser, the spectral broadening parts and the beat frequency signal detection, the complexity of spectral broadening is reduced and the stability of FOFC and the convenience for the frequency measurement are improved. With such an FOFC, the absolute frequencies of the I 2 -stabilized Nd:YAG 532 nm laser and I 2 -stabilized He-Ne 633 nm laser are measured. The experimenal results are in accordance with the recommended values by the International Committee for Weights and Measures.

Study of the femtosecond fiber comb and absolute optical frequency measurement

An optical frequency comb is built by using a commercial femtosecond laser and signal-noise (S/N) ratio of the f ceo signal is obtained to be about 30 dB. Its repetition rate frequency and offset frequency are highly stable and the tracking stability is verified. An absolute frequency measurement of a 1064 nm Nd: YAG laser is realized by using this stabilized optical frequency comb. The tracking stability of the repetition rate frequency is superior to 3.7×10 -14 at 100 s and the absolute frequency of the laser is 281630111757362 Hz. The experimental result is in accordance with the recommended value by International Committee of Weights & Measures(CIPM).

Temperature Controlled Filamentation in Argon Gas

Temperature controlled filamentation is experimentally demonstrated in a temperature gradient gas-filled tube. The proper position of the tube is heated by a furnace and two ends of the tube are cooled by air. The experimental results show that multiple filaments are shrunken into a single filament or no filament only by increasing the temperature at the beginning of the filament. This technique offers another degree of freedom of controlling the filamentation and opens a new way for intense monocycle pulse generation through gradient temperature in a noble gas.