In this study, heterodyne detection is adopted to measure the velocity of a target simulated by a rapidly rotating plate by using a mode-locked pulse laser as the resource. The coherent beat frequency of the signal light reflected by target and local oscillation light occurred on the surface of the detector. Then the waveform of beat frequency was processed by filtering to obtain the Doppler frequency shift of the signal light induced by target. With this frequency shift, the velocity of target could be obtained by calculation. Results indicate that the measurement has a high precision. The error on average is within 0.4 m/s.

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Two types of plasma shutters which can achieve pulse shaping of transversely excited atmospheric-pressure (TEA) Co2 laser are presented. We have designed two optical devices, which are plasma shutter and laser triggering spark gas (LTSG). The pulse forming network circuit used for precise triggering control is designed. In experiment, optical triggering gas free-breakdown plasma shutter and electrical triggering plasma shutter controlled via LTSG are researched for pulse shaping of the TEA CO2 laser. The collimated laser beam is focused at the center of two ZnSe lenses, producing an intensity of approximately 7x 1O'°W/cm2. In order to optimize truncated laser pulses, some operating parameters which include gas types filled in plasma shutter, gas pressure, LTSG 's voltage, and so on, are investigated via experiments. Using this technique, the nitrogen "tail" of the TEA CO2 laser pulse can be clipped, thus shortening the output laser pulse from the duration 6Ons to '3Ons.

For the nonlinearity of Fabry—Perot interferometer (FPI) transmission spectrum, the measurement uncertainty of incoherent Mie Doppler wind lidar based on it increases evidently with the increase of backscattering signal Doppler shift. A method of repeating the use of the approximate linear part of FPI transmission spectra for reducing the high uncertainty of a big Doppler shift is proposed. One of the ways of realizing this method is discussed in detail, in which the characteristics of FPI transmission spectrum changing with thickness and incident angle are utilized simultaneously. Under different atmosphere conditions, it has been proved theoretically that the range of measurement uncertainty drops to one-sixth while its minimum has no serious change. This method can be used not only to guide the new system design, but also as a new working way for the fabricated system.