Feinan Chen

Average Intensity and Spreading of Partially Coherent Four-Petal Gaussian Beams in Turbulent Atmosphere

The concept of partially coherent four-petal Gaussian (PCFPG) beam is introduced and described in analytical forms. Based on the Huygens-Fresnel integral formula, average intensity and beam spreading in turbulent atmosphere are derived in analytical expressions. Efiects of beam parameters and atmospheric structure constant on intensity distributions and efiective beam sizes are investigated in detail, respectively. Results show that PCFPG beams carrying larger coherence lengths or higher beam orders would be less afiected by turbulence. It is also indicated that, when the propagation distance increases, the PCFPG beam would convert into the Gauss- like proflle sooner or later, but this degradation can be reduced by modulating beam parameters. Results in this paper may provide potential applications in free-space optical communications.

Cross-spectrally pure light, cross-spectrally pure fields and statistical similarity in electromagnetic fields

This paper describes the concept of cross-spectrally pure light, implications of statistical similarity of an optical field on its cross-spectral purity and cross-spectrally pure fields. First, the concept of cross-spectral purity of light is analysed in the space-frequency domain by taking into account the vectorial nature of the radiation, and the conditions and reduction formula are obtained. Then, by utilizing statistical similarity, the relationship between cross-spectral purity and spatial coherence is explored in the electromagnetic field. Last, the conditions for cross-spectrally pure fields are discussed, the polychromatic plane wave and the far field produced by a planar, secondary, stochastic electromagnetic source are studied as examples, and moreover, the relationship between cross-spectral purity and spatial coherence, which we have drawn, is verified during the study.

Polarization Properties of Quasi-Homogeneous Beams Propagating in Oceanic Turbulence

Based on the extended Huygens-Fresnel principle and generalized Stokes theory, the evolution of polarization properties of beams generated by quasi-homogenous (QH) sources propagating in clear oceanic water was studied by the use of the oceanic turbulence spatial spectrum function. The results show that the beams have similar polarization self-reconstructed behavior under different turbulence conditions in the far field, but if the propagation distance is not long enough, the degree of polarization (DOP) fluctuates with much more complexity than state of polarization (SOP) of QH beams. The self-reconstructed ability of DOP at the special distance in turbulence would get to the best value if the values of coherence of width were chosen suitably, but for SOP, it has no best value.

Far-field radiation of coherent and incoherent combined Lorentz- Gaussian laser array

Formulas for the radiated intensity distributions of coherent and incoherent combined Lorentz-Gaussian beam array are respectively derived by utilizing representations of the cross-spectral density of the far field. Intensity distributions versus azimuth angles are depicted by numerical examples. Effects of beam array numbers and separate distances etc. on far-field radiated profiles are shown and analyzed. Comparisons between the phenomenon respectively induced by coherent and incoherent combinations of Lorentz-Gaussian beams are also made and further discussed. These results may provide potential applications in producing high-power double heterojunction laser arrays.

Far-field vectorial structure of a higher-order cosh-Gaussian beam

Based on the vector angular spectrum representation and the method of stationary phase, the vectorial structural characteristics of a higher-order cosh-Gaussian (HOCG) beam in the far field are investigated. Analytical expressions for the energy flux distributions of the TE term, TM term and the whole beam are derived and illustrated by numerical examples. Influences of beam orders and cosh parameters on energy flux distributions are analyzed, respectively. Furthermore, the discrepancy for the total energy flux distributions between the non-paraxial and paraxial cases is presented and analytical explanations for the phenomenon are also given.

VECTORIAL STRUCTURE OF A PHASE-FLIPPED GAUSS BEAM IN THE FAR FIELD

Based on the vectorial angular spectrum representation and the method of stationary phase, internal vectorial structures of a phase-∞ipped Gauss (PFG) beam difiracting in the far fleld are derived in analytical forms. The energy ∞ux for the TE term, TM term and the whole beam are derived and depicted by numerical examples. In∞uences of the f parameter on the whole energy ∞ux distributions are analyzed. Discrepancies of the whole energy ∞ux distributions between the paraxial and non-paraxial cases are shown in detailed manners. Furthermore, in∞uences of the f parameter on discrepancies between two cases are also studied.

Distant field detecting oriented modeling method of material surface scattering characteristic

Different materials have different surface scattering characteristics some of which are quite different from each other. These characteristics can be detected, measured and then matched with models of surface scattering characteristics of known materials in order to achieve the differentiating of materials in a distant range. In distant field detecting, some information of the scattered light could not be detected precisely for the detecting range is too distant. Therefore, these kinds of scattered light information should be eliminated in distant field detecting oriented modeling of material surface scattering characteristics. In the other hand, those kinds of scattered light information should be maintained which has not been changed after long range spreading in order to make the model of scattering characteristic simple and easy to be applied. The measuring of two chosen typical materials indicates that the differences of polarization states of the scattered light from their surfaces are obvious. Further theoretical arithmetic indicates that these kinds of differences maintained their significance after the scattered light has been spread for a distant range.