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Optics Letters

Optics Letters


  • Editor: Alan E. Willner
  • Vol. 37, Iss. 3 — Feb. 1, 2012
  • pp: 305–307

Longitudinal-differential interferometry: direct imaging of axial superluminal phase propagation

Myun-Sik Kim, Toralf Scharf, Christoph Etrich, Carsten Rockstuhl, and Hans Herzig Peter  »View Author Affiliations

Optics Letters, Vol. 37, Issue 3, pp. 305-307 (2012)

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We introduce and demonstrate a new interferometric method called longitudinal-differential (LD) interferometry, which measures the spatially resolved phase difference of the scattered field by an object relative to the illumination. This method is combined with a high-resolution interference microscope that allows recording three-dimensional field distributions in amplitude and phase. The method is applied to study the axial phase behavior of Arago spots, an effect observable in low-Fresnel-number systems behind objects with a size comparable to the wavelength. We directly observe the initial phase delay in the Arago spot and prove that the local phase velocity exceeds the speed of light in air. Such LD phase studies are applicable not only to the Arago spot but also to other kinds of light interactions with wavelength-scale objects, e.g., photonic nanojets.

© 2012 Optical Society of America

OCIS Codes
(050.5080) Diffraction and gratings : Phase shift
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.5050) Instrumentation, measurement, and metrology : Phase measurement
(180.3170) Microscopy : Interference microscopy
(260.1960) Physical optics : Diffraction theory
(260.3160) Physical optics : Interference

ToC Category:
Physical Optics

Original Manuscript: October 24, 2011
Manuscript Accepted: November 28, 2011
Published: January 19, 2012

Myun-Sik Kim, Toralf Scharf, Christoph Etrich, Carsten Rockstuhl, and Hans Herzig Peter, "Longitudinal-differential interferometry: direct imaging of axial superluminal phase propagation," Opt. Lett. 37, 305-307 (2012)

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