Offset local oscillator for cw laser Doppler anemometry

Using two CO(2) lasers with one frequency-locked to the other, we have developed a simple heterodyne cw Doppler backscatter anemometer for remote sensing. The configuration as tested in a lidar application requires no additional optics or detector over a homodyne setup. Spectra of the vertical wind show an example of the results available from a simple heterodyne Doppler lidar with a threshold of 0.25 m sec(-1) and an uncertainty of +/-10% in the velocity estimate.