Critically coupled resonators in vertical geometry using a planar mirror and a 5 nm thick absorbing film.

A (5.1+/-0.5) nm thick film of high oscillator strength J-aggregated dye critically couples to a single dielectric mirror, absorbing more than 97% of incident lambda = 591 nm wavelength light, corresponding to an effective absorption coefficient of (6.9+/-0.7) x 10(6) cm(-1) for (film thickness)/lambda < 1%.