  Femtosecond high-order harmonic transient absorption spectroscopy is used to
observe electromagnetically induced transparency-like behavior as well as
induced absorption in the extreme ultraviolet by laser dressing of the He 2s2p
(1Po) and 2p2 (1Se) double excitation states with an intense 800 nm field.
Probing in the vicinity of the 1s2 \to 2s2p transition at 60.15 eV reveals the
formation of an Autler-Townes doublet due to coherent coupling of the double
excitation states. Qualitative agreement with the experimental spectra is
obtained only when optical field ionization of both double excitation states
into the N = 2 continuum is included in the theoretical model. Because the Fano
q-parameter of the unperturbed probe transition is finite, the laser-dressed He
atom exhibits both enhanced transparency and absorption at negative and
positive probe energy detunings, respectively.
