Compared with the PC single cavity structure, the transmission ratio of the coupled cavity array increases more than three orders of magnitude, .

1a. With an additional control laser of very high intensity applied transverse to the cavity axis, the single-atom EIT condition is achieved and maximum transmission is recovered See Fig.

By varying the groove spacing, the diameter of the single or double diameter hole, and the rear air cavity depth and content, one can obtain absorption over a wide variety of frequencies.