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Different measures of speckle and coherence at the output of a multimode optical fiber

Journal Article · · Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Excitation of a multimode fiber with a focused spatially coherent light of finite bandwidth results in a partially coherent light at the output of the fiber. In this report, we observe the properties of speckle and classical coherence of such light with analytical theory, numerical modeling, and experimentally. Of particular interest is the relationship between measures of coherence and speckle and their dependence on input source bandwidth and fiber length. Speckle contrast is easy to measure experimentally and there exist at least two different methods to generate ensembles of random speckles. We demonstrate that speckle contrast evaluated over the ensemble of external diffusers is related to the number of effective modes—one of the characteristics of beam global coherence. The other speckle contrast measure evaluated over the ensemble of random bends and twists of the fiber is related to residual coherence, which is the pedestal on the average modulus of the complex degree of the coherence function on the output endface of the fiber.
Research Organization:
Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Organization:
USDOE; USDOE National Nuclear Security Administration (NNSA)
Grant/Contract Number:
89233218CNA000001; AC52-06NA25396
OSTI ID:
1571610
Alternate ID(s):
OSTI ID: 1484401
Report Number(s):
LA-UR--18-27749
Journal Information:
Journal of the Optical Society of America. A, Optics, Image Science, and Vision, Journal Name: Journal of the Optical Society of America. A, Optics, Image Science, and Vision Journal Issue: 1 Vol. 36; ISSN JOAOD6; ISSN 1084-7529
Publisher:
Optical Society of America (OSA)Copyright Statement
Country of Publication:
United States
Language:
English

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