A symmetrical method of optical heterodyning of the doppler shifted signal has been developed possessing minimal instrumental spectral broadening and high SNR. These advantages can be gainfully employed in measuring turbulence structure using a cw laser. The method employs two beams incident on the moving scatterer. The doppler signal frequency is independent of the scattering angle and the signal possesses no receiving aperture broadening. Typical values of signal-to-noise ratio are around 30 dB for a signal strength of 3 × 10−9 W. Optical alignment is simple. Relative merits of this technique compared to the local oscillator heterodyning method are briefly described.
© 1970 Optical Society of America
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