Licheng Zhang

Effects of non-Kolmogorov turbulence on the spiral spectrum of Hypergeometric-Gaussian laser beams.

We study the effects of non-Kolmogorov turbulence on the orbital angular momentum (OAM) of Hypergeometric-Gaussian (HyGG) beams in a paraxial atmospheric link. The received power and crosstalk power of OAM states of the HyGG beams are established. It is found that the hollowness parameter of the HyGG beams plays an important role in the received power and crosstalk power. The larger values of hollowness parameter give rise to the higher received power and lower crosstalk power. The results also show that the smaller OAM quantum number and longer wavelength of the launch beam may lead to the higher received power and lower crosstalk power.

Effects of low-order atmosphere-turbulence aberrations on the entangled orbital angular momentum states

Based on Zernike-model expansion of turbulence phase aberrations and non-Kolmogorov spectrum model of index-of-refraction fluctuation, we analyze the effects of low-order Zernike turbulence aberrations on orbital angular momentum (OAM) entanglement states in a weak fluctuation region. The signal photon detection probability of OAM entanglement states propagating in a slant turbulence channel with non-Kolmogorov turbulence Z-tilt, defocus, astigmatism, and coma aberrations are modeled, respectively. The results demonstrate that turbulence Z-tilt aberration is the dominant aberration, coma is the second, and astigmatism is the third, but that the defocus aberration has no impact on the detection probability. As the power-law exponent of the non-Kolmogorov spectrum increases from 3 to 4, the detection probability decreases.

Degree of Depolarization of Quantization Hermite-Gaussian Beam in a Turbulent Atmosphere

Based on quantum Stokes operators and non-Kolmogorov spectrum model of index-of-refraction ∞uctuation, the analytical for- mulas for the quantum degree of depolarization of quantization Hermite-Gaussian (QHG) beams propagating in a turbulent atmo- sphere slant channel are derived. The nonclassical polarization prop- erties of QHG beams propagating in turbulent atmosphere are stud- ied numerically. It is found that the polarization ∞uctuations of QHG beams are dependent of the turbulence factors such as spectrum power- law exponent, refractive index structure parameter at the ground and zenith angle. The degree of depolarization of QHG beams has a salta- tion and reaches the minimum value at spectrum power-law exponent fi = 11=3, the refractive index structure parameter at the ground of the turbulent atmosphere slightly afiects the polarization degree of QHG beams which have travelled a long distance, and the change of polariza- tion degree decreases with the increasing zenith angle. Furthermore, the numerical simulations show that QHG beams with higher photon- number level, lower beam order, shorter wavelength are less afiected by the turbulence. These results indicate that One can choose low-order QHG beams with wavelength ‚ = 690nm as optical carrier, increase photon number, set the size of transmitting aperture w0 as about 0.1m, and detect communication signals at the central region of beams to im- prove the performance of a polarization-encoded free-space quantum communication system.