  We present a bi-waveguide paradigm composed of joined Positive-Index-Material
PIM)/Negative-Index-Material (NIM) slabs, demonstrating ultra-slow light
propagation stemming from the competing propagation disposition in the PIM and
NIM regions. We report for the first time a mesoscopic extended electromagnetic
(EM) enhancement covering regions of the order of the free space wavelength,
enabled by the slow-light mode in our system. Our dynamic numerical results are
consistent with our developed theoretical model, predicting an EM energy
accumulation reminiscent of a charging capacitor. Our analysis reveals that
spatial compression is not a requirement to EM enhancement in slow-light
systems and stresses on the merits of high coupling efficiency, strong temporal
compression, monomodality and modal index bandwidth, -all present in our
proposed paradigm. Furthermore, we show that the heterostructure waveguide mode
is an extra-ordinary entity with a unique energy velocity, that is opposite to
the Poynting vector in one of the participant waveguides. We believe these
results will inspire new slow-light platforms relevant to the collective
harvesting of strong light-matter interactions.
