Electromagnetically induced grating

[1] EIGs can be used for purposes of atomic/molecular velocimetry,[2] to probe the material optical properties such as coherence and population life-times,[3] and switching and routing of light.

Figure 1 shows a possible beam configuration to write and read an EIG.

EB is referred as the "backward" reading beam and ER is the signal obtained by diffraction on the grating.

The phase-matching conditions for the EIG for the plane-wave approximation is given by the simple geometric relation:

are the frequencies of the writing (W, W') and reading beam (R), respectively, and n is the effective index of refraction of the medium.

The writing lasers form a grating by modulating density of matter or by localizing matter (trapping) on the regions of maxima (or minima) of the writing interference fields.

This type of grating can be easily tuned to produce multiple orders of diffraction.

[6] A grating where the writing lasers form a coherent matter pattern.

Figure 1 : Writing and reading an EIG
Figure 2 : Phase matching conditions for EIG diffraction
Figure 3 : Difference between a "matter grating" and a "population grating". The smileys :-( and :-) represent ground and optically excited atoms, respectively.