Liping Chang

Spectral shifts and spectral switches of light generated by scattering of arbitrary coherent waves from a quasi-homogeneous media

Within the accuracy of the Born approximation, it is shown that the light, which is generated by the scattering of an arbitrary coherent polychromatic wave from a quasi-homogeneous (QH) media can, display both spectral shifts and spectral switches. In our study, a pair of Youngs pinholes is utilized to modulate spatial coherence of the incident plane wave before it interacts with the scatterer. The spectral shifts are found to be highly dependent of the scattering angle, the correlation length of scatterer and the Youngs configuration parameter. Moreover, the spectral shifts can be converted from the red shift to blue one provided that the correlation length of scatterer is small enough. Derived results are confirmed by numerical simulations where influences of various factors on the spectrum are analyzed in detail.

Correlation between intensity fluctuations of electromagnetic waves scattered from a spatially quasi-homogeneous, anisotropic medium

Within the validity of the first-order Born approximation, expressions are derived for the correlation between intensity fluctuations (CIF) of an electromagnetic plane wave scattered from a spatially quasi-homogeneous (QH), anisotropic medium. Upon establishing the correlation matrix of the scattering potential of the medium, we show that the CIF is the summation of Fourier transforms of the strengths and normalized correlation coefficients (NCCs) of the scattering potential matrix. Numerical results reveal that the CIF is susceptible to the effective width and correlation length of the medium, and degree of polarization of the incident electromagnetic wave. Our study not only extends the current knowledge of the CIF of a scattered field but also provides an important reference to the study of high-order intensity correlations of light scattered from a spatially anisotropic medium.

Near-field evanescent waves scattered from a spatially deterministic and anisotropic medium

The scattering of light from an anisotropic medium, which may present either spatially random or deterministic statistics, has attracted substantial interest where the measurement of structural properties of scatterers is concerned. To date, however, no literature has studied near-zone evanescent waves scattered from a spatially deterministic and anisotropic medium. In this Letter, integral expressions are derived to represent electric fields of evanescent waves in the near-zone scattered field. In addition, the dependences of spectral densities of scattered field on the propagation distance of evanescent waves and effective radius of the scattering potential (ERSP) are also shown by numerical graphs, respectively. Potential applications of our study include the near-field optical microscopy and biomedical sensing.

Condition for invariant spectrum of an electromagnetic wave scattered from an anisotropic random media

Within the accuracy of the first-order Born approximation, sufficient conditions are derived for the invariance of spectrum of an electromagnetic wave, which is generated by the scattering of an electromagnetic plane wave from an anisotropic random media. We show that the following restrictions on properties of incident fields and the anisotropic media must be simultaneously satisfied: 1) the elements of the dielectric susceptibility matrix of the media must obey the scaling law; 2) the spectral components of the incident field are proportional to each other; 3) the second moments of the elements of the dielectric susceptibility matrix of the media are inversely proportional to the frequency.

Spectral Properties of Near-Field Evanescent Waves Scattered From a Particulate Medium With Adjustable Boundaries

Within the accuracy of the first-order Born approximation, expressions are derived for the spectrum of near-zone evanescent waves, which scatter from a spatially deterministic particulate medium with semisoft edges. By assuming that the scattering potential of the medium suffices the multi-Gaussian profile, it is shown that the degree of red-shifted spectrum of scattered field can be modulated by changing the summation index and effective radius of the scatterer. Moreover, the spectral switch, which transforms from the red shifts to the blue shifts of the spectrum, can emerge when the effective radius is sufficiently small compared with the incident wavelength. In addition, the summation index is another factor influencing the degree of spectral switches of near-zone scattered fields. These results are of potential applications to the near-field biomedical imaging and determination of scattering potentials of tiny particles.

Scattering of a Young’s diffractive electromagnetic light wave by quasi-homogeneous medium

While remaining accurate under the first-order Born approximation and the paraxial assumption, the scattering of a Youngs diffractive electromagnetic light wave by a quasi-homogeneous (QH) medium is specifically addressed in this study. Analytical expressions are derived for spectral density as well as the spectral degree of coherence of the scattered field. As long as the components of the complex amplitude of incident waves are proportional to each other, the resultant scattered light in the far field is proven to satisfy two reciprocity relations, namely, that the spectral density is proportional to the spatial Fourier transformation of the normalized correlation coefficient of the scattering potential, while the spectral degree of coherence is dependent only on the spatial Fourier transformation of the strength of the scattering potential.

Reciprocal Relations for Third-Order Correlation Between Intensity Fluctuations of Light Scattered From a Quasi-Homogeneous Medium

Within the validity of the first-order Born approximation, we introduce the third-order correlation between intensity fluctuation (CIF) of light scattered from a quasi-homogeneous medium. The third-order CIF is defined as the degree of intensity correlations specified at three position vectors in scattered field. Expressions are derived for the normalized CIF and variance in intensity fluctuations (VIF) of the scattered field. Two reciprocal relations are generalized for the third-order CIF of the scattered field: 1) The normalized CIF is proportional to the real portion of the Fourier transform products of the strength of the scattering potential; 2) the third-order VIF of the scattered field is proportional to the cube of the Fourier transform of the normalized correlation coefficient of the scattering potential.