Quenching

The term quenching has many different meanings; This article only discusses fluorescence quenching, which refers to all the phenomena that lead to a decrease in the fluorescence intensity and lifetime of a particular substance. In rare-earth-doped or transition metal-doped laser gain media (laser crystals or glasses), the up-electron energy level lifetime of the laser active ions is sometimes greatly reduced.

Factors resulting from quenching:

• Multiple phonon jumps to a lower electronic level.
• The process of energy transfer between laser active ions (for high concentrations, especially when ion clusters occur; This is called concentration quenching.
• The energy is transferred to other ions, for example as unwanted impurities that can be introduced by raw materials or during crystal growth, such as contamination from crucibles.
• The energy is transferred to the color center, i.e. to a defect in the crystal structure.

In this case, one might think that the higher electron energy level is quenched, or that the radiation jumps to a lower energy level. Quenching becomes evident as the decay time and the total intensity of fluorescence from the quenched electronic state decreases. The decrease in intensity is associated with a decrease in quantum efficiency, and some ions that enter the upper layer fluoresce.

If the upper laser of some laser conversions is quenched, i.e., the lifetime of the upper state is reduced, i.e., the lifetime of the upper energy state is reduced, which increases the threshold pump power of the laser or decreases the gain of the amplifier. However, the quenching process is also very helpful and even essential for laser operation:

• They can be filled with upper laser levels by pumping to a higher level.
• They may help to reduce the lifetime of the low-energy state, thereby reducing the number of low-level laser light levels.