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Updated: Jun 11, 2026

New Framework for Understanding Cross-Brain Coherence in Functional Near-Infrared Spectroscopy (fNIRS) Hyperscanning Studies
Published on: October 6, 2023
Experimental study of the relation between the degrees of coherence in space-time and space-frequency domain
Bhaskar Kanseri1, Hem Chandra Kandpal
1Optical Radiation Standards, National Physical Laboratory (Council of Scientific and Industrial Research), New Delhi, 110012 India. kanserib@mail.nplindia.ernet.in
Abstract:
We present an experimental study showing the effect of the change in the bandwidth of light on the magnitude of both the complex degree of coherence and the spectral degree of coherence at a pair of points in the cross-section of a beam. A variable bandwidth source with a Young's interferometer is utilized to produce the interference fringes. We also report for the first time that if the field is quasi-monochromatic or sufficiently narrowband, the elements of both the beam coherence polarization matrix and the cross-spectral density matrix, normalized to intensities (spectral densities) at the two points possess identical values.
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