  We extend the concept of shortcut to adiabaticity to full-wave optics and
provide application to the design of an ultra-compact waveguide junction. In
particular, we introduce a procedure allowing one to synthesize a purely
dielectric optical potential that precisely compensates for the non-adiabatic
losses of the transverse-electric fundamental mode in any (sufficiently
regular) two-dimensional waveguide junction. Our results are corroborated by
finite-element method numerical simulations in a Poschl-Teller waveguide mode
expander.
