We perform a long distance measurement up to 1.2 km on the outdoor baseline by electro-optic dual-comb interferometry. A frequency comb pair is developed by phase modulating a continuous laser with a narrow linewidth, and the slightly different repetition frequencies are synchronized to the Rb clock via the signal generators. A RF electrical comb can be generated by multi-wavelength heterodyne interferometry, and thus, a series of synthetic wavelengths can be obtained, whose phases can be used to determine the distances. Compared with the reference values, the experimental results show an agreement within 379 μm in the 1180 m range. In the long-time experiments, the Allan deviation can be below 20 μm with an averaging time of 10 s, and can be further improved to be less than 600 nm when the averaging time is above 350 s at 435 m and 1180 m, respectively.

An electro-optic dual-comb Doppler velocimeter for high-accuracy velocity measurement is presented in this paper. The velocity information of the object can be accurately extracted from the change of repetition frequency, which is in the microwave frequency domain and can be locked to an atomic clock. We generate two optical combs by electro-optic phase modulators and trace their repetition frequencies to the rubidium clock. One functions as the measurement laser and the other the reference. Experimentally, we verify its high accuracy in the range of 100–300 mm/s with a maximum deviation of 0.44 mm/s. The proposed velocimeter combines the merits of high accuracy and wide range. In addition, since the repetition frequency used for the measurement is traceable to the rubidium clock, its potential superiority in traceability can be utilized in velocity metrology.

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Based on the dielectric property of carbon nanotube film, the surface plasmon ploariton propagation and localization phenomena on the carbon nanotube film are investigated using THz time-domain spectroscopy technique. The simulation results show that in the gate period of 168um, the resonance peaks of surface plasmon mode are at 0.99THz and 1.95 THz, which are consistent with the theoretical results. Further analysis demonstrates that both the gate thickness and the width have an important effect on the properties of surface plasmon ploaritons.

In this paper, we develop a method to measure the refractive index of liquid at different temperatures applying the femtosecond laser frequency comb. The measurement principle is to test the phase changes of the measuring signal caused by light traveling through the liquid, then calculating the refractive index according to the phase difference between water and air. The experiment on measuring the water refractive index at temperature from 20 o C to 60 o C was performed, and the measuring results show a satisfactory accuracy.