scholarly journals Linear Combinations of the Complex Degrees of Coherence

Photonics ◽  
2021 ◽  
Vol 8 (5) ◽  
pp. 146
Author(s):  
Zhangrong Mei ◽  
Olga Korotkova
Keyword(s):  
Spatial Coherence ◽  
Light Fields ◽  
Linear Combinations

We propose a method for structuring the spatial coherence state of light via mixed linear combinations of N complex degrees of coherence (CDC) and specify the conditions under which such combinations represent a valid CDC. Several examples demonstrate that this method opens previously unknown avenues for modeling random sources, radiating to light fields with unique features.

Spatial coherence effects in second-harmonic generation of scalar light fields

2021 ◽  
Author(s):  
Henri Atte Pesonen ◽  
Atri Halder ◽  
Juha-Matti Huusko ◽  
Ari T Friberg ◽  
Tero Setälä ◽  
...  
Keyword(s):  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Second Harmonic ◽  
Spatial Coherence ◽  
Light Fields ◽  
Coherence Effects

scholarly journals Spatial Coherence Manipulation on the Statistical Photonic Platform

2021 ◽  
Author(s):  
Leixin Liu ◽  
Wenwei Liu ◽  
Fei Wang ◽  
Hua Cheng ◽  
Duk-Yong Choi ◽  
...  
Keyword(s):  
Phase Distribution ◽  
Random Phase ◽  
Spatial Coherence ◽  
Light Fields ◽  
Optical Components ◽  
Partially Coherent ◽  
Optical Media ◽  
Partially Coherent Light ◽  
Coherent Beams ◽  
Coherent Vortex

Abstract Coherence, like amplitude, polarization and phase, is a fundamental characteristic of the light fields and is dominated by the statistical optical property. Generally, accurate coherence manipulation is challenging since coherence as a statistical quantity requires the combination of various bulky optical components and fast tuning of optical media. Spatial coherence as another pivotal optical dimension still has not been significantly manipulated on the photonic platform. Here, we theoretically and experimentally realize accurate manipulation of the spatial coherence of light fields by loading a temporal random phase distribution onto the wave-front on the statistical photonic platform. By quantitatively manipulating the statistical photonic properties, we can successfully achieve the partially coherent light with the pre-defined degree of coherence and continuously modulate it from fully coherent to incoherent. This design strategy can also be easily extended to manipulate the spatial coherence of other special beams such as partially coherent vortex beam generations. Our approach provides straightforward rules to manipulate the coherence of the light fields and paves the way for applications of partially coherent beams in information encryption, ghost imaging, and information transmission in turbulent media.

scholarly journals Optical Coherence Encryption with Structured Random Light

2021 ◽  
Author(s):  
Demin Peng ◽  
Zhaofeng Huang ◽  
Yonglei Liu ◽  
Yahong Chen ◽  
Fei Wang ◽  
...  
Keyword(s):  
Light Propagation ◽  
Fractional Fourier Transform ◽  
Spatial Coherence ◽  
Statistical Characteristics ◽  
Light Fields ◽  
Complex Environments ◽  
Optical Encryption ◽  
First Order ◽  
Encryption Method ◽  
Promising Avenue

Abstract Information encryption with optical technologies has become increasingly important due to remarkable multidimensional capabilities of light fields. However, the optical encryption protocols proposed to date have been primarily based on the first-order field characteristics, such as the optical field amplitude and phase as well as its polarization. As the said first-order characteristics of light fields are strongly affected by interference effects, the conventional encoding protocols become quite unstable during light propagation and interaction with the matter. Here, we introduce an alternative optical encryption protocol whereby the information is encoded into the spatial coherence distribution of a structured random light beam via a generalized van Cittert--Zernike theorem. We show that the proposed approach has two key advantages over its conventional counterparts. First, the complexity of measuring the spatial coherence distribution of light enhances the encryption protocol security. Second, the relative insensitivity of the second-order statistical characteristics of light to environmental noise makes the protocol robust against the environmental fluctuations, e.g, the atmospheric turbulence. We carry out experiments to demonstrate the feasibility of the coherence-based encryption method with the aid of a fractional Fourier transform. Our results open up a promising avenue for further research into optical encryption in complex environments.

Quanitative aspects of electron diffraction using electron holography

1995 ◽  
Vol 53 ◽  
pp. 616-617
Author(s):  
E. Völkl ◽  
L.F. Allard ◽  
B. Frost ◽  
T.A. Nolan
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Software Package ◽  
Spatial Coherence ◽  
Electron Holography ◽  
Image Intensity ◽  
Interference Fringes ◽  
Complex Image ◽  
The Difference ◽  
Recorded Image

Off-axis electron holography has the well known ability to preserve the complex image wave within the final, recorded image. This final image described by I(x,y) = I(r) contains contributions from the image intensity of the elastically scattered electrons IeI (r) = |A(r) exp (iΦ(r)) |, the contributions from the inelastically scattered electrons IineI (r), and the complex image wave Ψ = A(r) exp(iΦ(r)) as:(1) I(r) = IeI (r) + Iinel (r) + μ A(r) cos(2π Δk r + Φ(r))where the constant μ describes the contrast of the interference fringes which are related to the spatial coherence of the electron beam, and Φk is the resulting vector of the difference of the wavefront vectors of the two overlaping beams. Using a software package like HoloWorks, the complex image wave Ψ can be extracted.

An Alternate Algorithm for (3x3) Median Filtering of Digital Images

2012 ◽  
Vol 2 (1) ◽  
pp. 7-9 ◽  
Author(s):  
Satinderjit Singh
Keyword(s):  
Median Filter ◽  
Computational Cost ◽  
Spatial Coherence ◽  
General Purpose ◽  
Median Filtering ◽  
Basic Algorithm ◽  
Temporal Complexity ◽  
Filter Kernel ◽  
One Step ◽  
High Computational Cost

Median filtering is a commonly used technique in image processing. The main problem of the median filter is its high computational cost (for sorting N pixels, the temporal complexity is O(N·log N), even with the most efficient sorting algorithms). When the median filter must be carried out in real time, the software implementation in general-purpose processorsdoes not usually give good results. This Paper presents an efficient algorithm for median filtering with a 3x3 filter kernel with only about 9 comparisons per pixel using spatial coherence between neighboring filter computations. The basic algorithm calculates two medians in one step and reuses sorted slices of three vertical neighboring pixels. An extension of this algorithm for 2D spatial coherence is also examined, which calculates four medians per step.

Light intensity and spatial coherence characteristics of laser coherent detection in a turbulent atmosphere

2020 ◽  
Vol 13 (4) ◽  
pp. 728-736
Author(s):  
REN Jian-ying ◽  
◽  
◽  
SUN Hua-yan ◽  
ZHAO Yan-zhong ◽  
...  
Keyword(s):  
Light Intensity ◽  
Turbulent Atmosphere ◽  
Spatial Coherence ◽  
Coherent Detection
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