  Evanescent waves are central to many technologies such as near-field imaging
that beats the diffraction limit and plasmonic devices. Frustrated total
internal reflection (FTIR) is an experimental method commonly used to study
evanescent waves. In this paper, we shape the incident beam of the FTIR process
with a Mach-Zehnder interferometer and measure light transmittance while
varying the path length difference and interferometric visibility. Our results
show that the transmittance varies with the path length difference and, thus,
the intensity distribution of the shaped beam. Experiment and finite element
method simulation produce results that agree. We also show, through
simulations, that the transmittance can be controlled via other methods of beam
shaping. Our work provides a proof-of-concept demonstration of the coherent
control of the FTIR process, which could lead to advancements in numerous
applications of evanescent waves and FTIR.
