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Spatial coherence measurement of polychromatic light with modified Young's interferometer
Kimmo Saastamoinen1, Jani Tervo, Jari Turunen
1University of Eastern Finland, Department of Physics and Mathematics, P. O. Box 111, FI-80101 Joensuu, Finland. kimmo.saastamoinen@uef.fi
Optics Express
|March 14, 2013
Summary
Partial spatial coherence measurement is now possible for polychromatic light. A modified Young
Area of Science:
- Optics and Photonics
- Wave Phenomena
- Coherence Theory
Background:
- Partial spatial coherence is crucial in optical systems.
- The normalized mutual coherence function quantifies spatial coherence.
- Young's two-pinhole interferometer measures coherence for narrowband light but fails for polychromatic light due to diffraction's wavelength dependence.
Purpose of the Study:
- To develop a method for measuring the degree of spatial coherence for polychromatic light.
- To restore the applicability of Young's two-pinhole interferometer for arbitrary spectral widths.
Main Methods:
- Modification of the classic Young's two-pinhole interferometer with an achromatic Fresnel transformer.
- Theoretical analysis of the modified interferometer's performance with polychromatic radiation.
- Experimental validation of the theoretical predictions.
Main Results:
- The degree of spatial coherence for polychromatic light is demonstrated to be related to the visibility of intensity fringes.
- The modified interferometer overcomes the limitations of the classic setup for broadband light.
- The measurement of spatial coherence is re-established for light beams of arbitrary spectral widths.
Conclusions:
- The modified two-beam interferometer with an achromatic Fresnel transformer successfully measures the degree of spatial coherence for polychromatic light.
- This work validates the theoretical and experimental feasibility of using fringe visibility for broadband spatial coherence measurements.
- The study re-establishes the Young's two-pinhole interferometer as a versatile tool for coherence measurements across various spectral widths.
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