Modulated light absorption and emission of a luminescent layer by phase-controlled multiple beam illumination.

We propose a multiple beam illumination scheme to control the intensity of the light emitted by a thin luminescent layer. The experiment is designed to get as close as possible to the condition of Coherent Perfect Absorption (CPA) at a wavelength at which the absorption coefficient of the luminescent layer is low, and it is realized by externally acting on the phase difference between the incident beams. We elucidate experimental limitations that prevent the achievement of CPA in these slabs. Nevertheless, we are able to demonstrate that when the two beams destructively interfere outside the luminescent layer, the incident light is more efficiently absorbed by the luminescent layer and the intensity of the emitted light is phase-modulated.