1. Theoretical and experimental study of the laser propagation characteristics in the atmosphere
The atmospheric propagation effect is one of the important factors in the application of various space laser systems. By analyzing and simulating the influence of atmospheric attenuation, atmospheric thermal blooming and atmosphere turbulence on the laser propagation systematically, our research group has provided theoretical basis for the applications of laser systems.
(1) Propagation characteristics of array beams through atmosphere turbulence
Figure 1. Light intensity distribution of random phase radial array beams in the atmosphere turbulence of different intensity
Figure 2. Spatial coherence of radial GSM array beams in free space and atmosphere turbulence
(2) Atmospheric turbulence simulation system
Atmosphere turbulence can be generated by experimental system in our laboratory. Quantitative estimation of the characteristics of turbulence in the mesosphere and lower thermosphere have been derived. Those establish the preliminary foundation and experimental verification for different laser systems in atmosphere turbulence.
In order to examine the performance of adaptive optics system in the laboratory environment, a hot-wind laboratory atmosphere turbulence simulator is developed which uses the hot resistance coil to generate the hot air turbulence and the fan to control the intensity of the turbulence.
Figure 3. Atmosphere turbulence simulation system (left). light power spectrum(right)
An oil-bath turbulence simulator mounted in the laboratory. It heats liquid and comes into being convection, which is emerged from the temperature difference between the upper and lower part in the heating process. And this can simulate the environment of atmosphere turbulence and water turbulence.
(3) Simulation software for laser atmospheric propagation characteristics
Aiming at the various effects of laser propagation in the atmosphere, our research group has carried out profound research and theoretical simulation, and developed the simulation software for laser atmospheric propagation characteristics.
This software is divided into four components:
1. refractive index structure constant in visible/near-infrared wavebands
2. atmospheric turbulence effect
3. atmospheric attenuation effect
4. propagation characteristics of laser pulses in turbulent and randomly distributed particles
2. A theoretical study of the under water laser propagation characteristics
At present, the research on the laser beams propagating in oceanic turbulence is a new field，so it is of great significance to study the propagation characteristics of different beam models in oceanic turbulence. Aiming at the air-sea interface and seawater, our research group studies its effects on the laser propagation. Finally, the downlink channel model is established based on the sea-fog and the energy attenuation characteristics of laser downlink communication is simulated.
Figure 4. Laser transmittance varies with the propagation distance(left) and transmission angle(right) for different values of wind speeds and visibility.
Figure 5. Average light intensity of the coherent synthetic radial GSM array beams at different values of propagation distances
