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.

The laser head can dolly move, up and down move, rotary move. The Z axis apply precision motor organ, it is better for medium mould repairing.

Liquid crystals were chosen because their strong birefringence provides a simple way to observe their rotation around the laser beam axis.