Early versions of these devices were monochromatic,  and all of them produce an output that is very coherent.
Some of these devices use exciplexes [EKS-ih-pleks-es], which are sometimes referred to as excited   dimers [DY-mers], or excimers [EKS-ih-mers]. Those substances disintegrate when they are in the  ground state, which means that a majority of them are in the excited state, a condition known as   population inversion. That population inversion takes place within the gain medium of these devices,  which is typically placed in an optical cavity. Early versions of these devices were monochromatic,  and all of them produce an output that is very coherent. Name these devices capable of producing a  very focused beam of light that can be used to read barcodes or DVDs.
Some of these devices use exciplexes [EKS-ih-pleks-es], which are sometimes referred to as excited   dimers [DY-mers], or excimers [EKS-ih-mers].
lasers