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Updated: Aug 1, 2026

Measurement of Coherence Decay in GaMnAs Using Femtosecond Four-wave Mixing
Published on: December 3, 2013
Nonequivalence of spatial shifts and Wigner delays at interfaces
Christophe Bonnet1, Dominique Chauvat, Olivier Emile
1Laboratoire d'Electronique Quantique-Physique des Lasers, Unité Mixte de Recherche CNRS-Université 6627 PALMS, Université de Rennes I, Campus de Beaulieu, F-35042 Rennes, France.
Abstract:
We isolate spatial shifts and Wigner delays for reflection at the same interface and demonstrate that they can carry different information. The spatial shifts associated with Wood anomalies on gratings can be either positive or negative, while the corresponding delays are both positive. In the standard case of total reflection at a glass-air interface, a differential two-photon absorption correlation technique allows us to measure for the first time a delay of up to 35 fs in agreement with the associated 10.5 microm spatial shift. The method also allows us to isolate giant Wigner delays. The existence of similar delays in different areas of physics is discussed.
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