Evanescent-field Mach-Zehnder interferometer

Abstract

We propose an evanescent-field interferometer in the Mach-Zehnder configuration, which can provide an interferometric measure of the phase of evanescent fields and can be used to quantify the Hartman effect. The phase difference for such tunneled fields saturates to $\ensuremath{\pi}/2$, thus confirming the classic Hartman effect. An analytical model of the proposed evanescent-field interferometer is presented and validated by numerical simulations based on the finite-difference time-domain technique. In the numerical treatment, the requisite elements of the interferometer, such as beam splitters and mirrors, are realized through carefully designed cavities in a two-dimensional photonic crystal system. The underlying cavity modes are further engineered using a weak perturbation to spatially maneuver the evanescent field along preferred directions. The evanescent-field interferometer offers multiple avenues of introducing phase delay and has higher sensitivity that is spatially delocalized in comparison to the conventional propagating-field interferometers.