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H. Lemmel:
"Dispersion cancellation in a triple Laue interferometer";
Journal of Optics, 16 (2014), 10; S. 105704.

The concept of dispersion cancellation has been established in light optics to improve the
resolution of interferometric measurements on dispersive media. Odd order dispersion
cancellation allows to measure phase shifts without defocusing the interferometer due to wave
packet displacements, while even order dispersion cancellation allows to measure time lags
without losing resolution due to wave packet spreading. We report that either type of dispersion
cancellation can be realized very easily in a triple Laue interferometer. Such interferometers are
Mach - Zehnder interferometers based on Bragg diffraction, and are commonly used for neutrons
and x-rays. Although the fi rst x-ray interferometer was built nearly fi ve decades ago, the feature
of dispersion cancellation hasn ʼ t been recognized so far because the concept was hardly known
in the neutron and x-ray community. However, it explains right away the surprising decoupling
of phase shift and spatial displacement that we have discovered recently in neutron
interferometry (Lemmel and Wagh 2010 Phys. Rev. A 82 033626). Furthermore, this article
might inspire the light optics community to consider whether a triple Laue interferometer for
laser light would be useful and feasible. We explain how dispersion cancellation works in
neutron interferometry, and we describe the setup rigorously by solving the Schrödinger
equation and by calculating the path integral. We point out, that the latter has to be evaluated
with special care since in our setup the beam trajectory moves with respect to the crystal lattice
of the interferometer.

interferometry, dispersion cancellation, Bragg diffraction

http://dx.doi.org/10.1088/2040-8978/16/10/105704