Experimental Study on Influence of Atmospheric Turbulence on Coherence of Dual-Frequency Laser

Abstract

The influence of atmospheric turbulence on the coherence of a dual-frequency laser beam is studied experimentally. An atmospheric turbulence simulator is inserted in one arm of a Mach-Zehnder interferometer. A single frequency laser beam and a dual-frequency laser beam with a frequency difference of 100 MHz travel through the interferometer, respectively. The visibilities of the interference fringes of the single and dual-frequency laser beams under different turbulent forces are compared. When the turbulence becomes stronger, the visibilities of the interference pattern of the single frequency interferometer decrease more rapidly. This shows that the atmospheric turbulence has less influence on the coherence of the dual-frequency laser beam. The linewidths broadened by the turbulence are calculated with the Wiener-Khintchine theory.

A dual‐frequency continuous wave doppler lidar for velocity measurement at far distance

“…However, the adaptability of conventional single-frequency coherent lidar system is limited due to the degradation of coherence caused by atmospheric turbulence, which seriously affected the detect precision of lidar. 5,6 And in speed measurement, the speckle noise from the rough target surface causes a spectral bandwidth broadening of Doppler shift 7 ; thus, the velocity resolution is reduced. In response to the above problems, a new type of coherent Dual-Frequency (DF) lidar has been introduced and developed.…”

“…Due to these characteristics, the lidar has a high performance in finding, aviation safety, automatic driving, and so on. However, the adaptability of conventional single‐frequency coherent lidar system is limited due to the degradation of coherence caused by atmospheric turbulence, which seriously affected the detect precision of lidar 5,6 . And in speed measurement, the speckle noise from the rough target surface causes a spectral bandwidth broadening of Doppler shift 7 ; thus, the velocity resolution is reduced.…”