Laser Atmospheric Transmission Spectra Change

In recent years， the spectral changes of laser beams in atmosphericturbulence is one of focus leading subjects in the area of optics and laserindustry at home and abroad. The research work can provide the theoreticalmodel and computational basis for the application of free space opticalcommunications in practice. The present work is devoted to studying spectralchanges of laser beams propagating through non-Kolmogorov atmosphericturbulence. This main work and researching result will be given as follows:1. Based on the non-Kolmogorov spectrum, using the extendedHuygens-Fresnel principle, the analytical expressions for the spectrum ofGaussian Schell-model (GSM) beams and Rectangular Array GaussianSchell-model (RAGSM) beams propagating through non-Kolmogorovatmospheric turbulence are derived and used to study the influence ofnon-Kolmogorov atmospheric turbulence on spectral changes of beams.2. There exist spectral shifts (blue shift and red shift) and spectral transitionwhen GSM beams propagating through non-Kolmogorov atmosphericturbulence. The spectral transition depends on the off-axis distance r, thegeneral exponent α, the general structure constantC~2n, the inner scale l0, theouter scale L0, and the propagation distance z. With the increment of the generalexponent α and the inner scale l0, as well as the decrement of the generalstructure constantC~2n, the spectral transition magnitude△will decrease and thecritical position of spectral transition zcwill increase. Then the spectral changesare less affected by the change of outer scale L0.3. The correlated and uncorrelated superposition RAGSM beamspropagating through non-Kolmogorov atmospheric turbulence, the spectralchanges depends on the number of beamlets M, N, the separation distances X, Y,the off-axis distance r, the general exponent α, the general structure constantC~2n,the inner scale l0, the outer scale L0, and the propagation distance z; with theincrement of the general exponent α and the inner scale l0, as well as thedecrement of the number of beamlets M, N and the general structure constant C~2n, the on-axis relative spectral blue shift maximum value will increase, theoff-axis the spectral transition magnitude△will decrease and the criticalposition of spectral transition ρxcwill decrease. And with the increment of theseparation distances X, Y, the critical position of spectral transition ρxcwillincrease. The spectral changes are not obvious affected by the change of outerscale L0.4. The on-axis coherent superposition RAGSM beams of spectral presentsthe blue-shift alternating with the red-shift, rather than incoherent superpositionRAGSM beams of spectral will only exhibit blue-shift. The correlatedsuperposition RAGSM beam for relative spectral blue shift maximum value, thespectral transition magnitude△and the critical position of spectral transitionρxcare smaller than the uncorrelated superposition RAGSM beam.