Coherent tunneling by adiabatic passage in an optical waveguide system

We report on an experimental demonstration of light transfer in an engineered triple-well optical waveguide
structure which provides a classic analog of coherent tunneling by adiabatic passage (CTAP) recently proposed
for coherent transport in space of neutral atoms or electrons among tunneling-coupled optical traps or quantum
wells (A. D. Greentree et al., Phys. Rev. B 70, 235317 (2004); K. Eckert et al., Phys. Rev. A 70, 023606
(2004)). The direct visualization of CTAP wave-packet dynamics enabled by our simple optical system clearly
shows that in the counterintuitive passage scheme light waves tunnel between the two outer wells without
appreciable excitation of the middle well.