Ceramic Gain Medium

definition:
Laser gain medium with ceramic microstructure.

Generally speaking, solid-state gain media are crystals or glass. Crystals are usually single crystals because polycrystalline media typically have strong scattering at boundaries. However, since the 1990s, a polycrystalline medium - ceramics - has greatly reduced scattering losses through fine preparation techniques, especially using vacuum sintering technology.
At the beginning, very small ions were used in the powder, and then refined to produce nano ions with controllable sizes, very small microcrystals, and pores, resulting in scattering losses not much greater than single crystals. Especially achieved in yttrium aluminum garnet. Nd doped YAG ceramics can achieve the same laser efficiency as Nd doped YAG single crystals.
Ytterbium doped gain media also exhibit the same performance. Ceramics can also be used as electronic vibration laser gain media.  
Ceramic laser gain media have many important advantages compared to single crystals:

1. The preparation cost is low, especially when making very large pieces.  
2. Ceramic gain media can be made into any shape and size, but single crystal growth technology limits the size of the media.  
3. Ceramics can also produce composite gain media, including different doping levels and even different dopants. It can also include a saturable absorber for passive Q-switching.  
4. It is easy to obtain doping concentrations with spatial variations. This can provide additional degrees of freedom for laser design.  
5. For neodymium doped and ytterbium doped YAG ceramics, higher doping concentrations can be achieved without causing quenching effects that reduce laser efficiency.  
6. Some materials, such as yttrium oxide (Y2O3), scandium oxide (Sc2O3), and other titanium oxides, have high melting points and are difficult to grow into single crystals, but they are easily obtained in ceramic form because the sintering temperature is much lower than the melting temperature. The high thermal conductivity of Y2O3 and Sc2O3 is superior to YAG in these materials.  

Based on the above reasons, ceramic gain media can replace Dai Jing in many cases, especially in large volume applications and situations that require large gain media.  
It should be noted that ceramics can not only be used as gain media in lasers. Some gain media, such as aluminum nitride ceramics, have high thermal conductivity and can serve as excellent electrical insulators. This also allows them to be used as heat sinks in high-power laser diodes.