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Title: Focusing of partially coherent light by a graded-index lens

We use coherence theory to study how the focusing of an optical beam by a graded-index (GRIN) lens is affected when the incoming beam is only partially coherent. The Gaussian–Schell model is used to show that the intensity of a partially coherent beam exhibits self-imaging and evolves in a periodic fashion in a GRIN medium with a parabolic index profile. Spatial coherence of the beam affects a single parameter that governs how much the beam is compressed at the focal point. Our results show that the focal spot size depends on the fraction of the beam’s diameter over which coherence persists. Focusing ceases to occur, and the beam may even expand at the focal point of a GRIN lens, when this fraction is below 10%.

 
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NSF-PAR ID:
10390067
Author(s) / Creator(s):
Publisher / Repository:
Optical Society of America
Date Published:
Journal Name:
Optics Letters
Volume:
48
Issue:
2
ISSN:
0146-9592; OPLEDP
Page Range / eLocation ID:
Article No. 436
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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