Optical pumping is a process in which light energy is used to excite electrons from a lower to higher energy level. It was first developed by Alfred Kastler in the early 1950s and is primarily used to pump laser medium during laser construction. It can also pump electrons that are bound with a molecule or an atom to a well-defined quantum state.
When a system consisting of atoms with random orientation of magnetic fields is optically pumped, the individual magnetic fields of atoms will be realigned towards the direction of light. This results in the rearrangement of magnetic energy levels. In some cases, a group of atoms will be oriented to create a magnetic field within the system.
Optical pumping often takes place in laser action which involves absorption of photons of light to raise the energy levels of electrons. These electrons remain at higher energy state until they are activated to release their stored energy in the form of a laser beam. Several types of lasers can be optically pumped. The most common optically pumped lasers are doped-insulator solid-state lasers consisting of glass, ceramic or laser crystal host medium.
Some of the common optical pump sources include:
- Laser diodes
- Discharge lamps
- Other types of laser sources such as dye lasers pumped with gas lasers and titanium-sapphire lasers pumped with solid-state lasers
High power conversion efficiency of optically pumped lasers can be achieved upon efficient absorption of pump light in the gain medium. The pump absorption efficiency, in some cases can be increased by transmitting light via multiple passages in the gain medium.