Reflectivity comb in coherently dressed three-level media

The photonic density of states of a light beam propagating through ultracold atoms may be easily modified by modulating the atomic susceptibility with a light grating. This was predicted and observed in a resonantly absorbing atomic sample supporting electromagnetically induced transparency where a probe nearly resonant with a standing wave coupling beam experiences a fully developed stop-band. In the present work, a probe that is resonant with higher harmonics of the standing wave frequency in a highly asymmetric three-level Lambda-configuration or a ladder configuration, is predicted to exhibit a peculiar multipeak all-optically tunable reflection pattern. Such an unusual reflectivity spectrum is shown to be related to a suppression of the absorption akin to the Borrmann effect in the dynamical X-ray diffraction in crystals. This novel effect can actually be observed in atomic hydrogen but also in a variety of atoms, such as, for example, strontium, provided the optical lattice has been angle-tuned.