Question

Give a simple explanation for each part. A few phrases will suffice. Detailed explanation is not needed. a) How is population inversion acquired in a laser diode? b) What does XPM stand for? When does it occur?

Answer 1

a.

In most situations, the majority of atoms in a gas are in their ground state. Population inversion refers to the opposite situation, when most of the atoms in a gas are in an excited state. A laser produces light by the process of stimulated emission. Here, atoms in an excited state are stimulated by incident photons to decay to their ground state, emitting an identical photon in the process. The process therefore requires a gas of atoms residing in metastable excited states—a population inversion.

b.

XPM stands for Extensible Metadata Platform, which was created exclusively by Adobe for use with its programs. XPM allows programs to collect metadata in an easy and simple way, as well as keeping it up-to-date in real time while the project is being edited.