Introducing the “Soul” of solid-state lasers

Introducing the “Soul” of solid-state lasers

Mainstream solid-state laser materials

The core of any laser is the laser working substance, and the working substance of a solid-state laser is essentially solid. Most solid-state laser media are composed of crystal matrices and doped atoms or ions with laser activity, while amorphous (glass) matrices are relatively rare. The latest development in ceramic preparation technology is expected to significantly expand the application scope of low-cost and high-quality laser materials, which can be made in a size much larger than that of crystal materials.

Core commonly used solid-state laser materials

Ruby: Its chemical composition is chromium-doped aluminum oxide (Cr:Al₂O₃). Artificial rubies have a similar chemical composition to gem-quality rubies, but they are of higher purity and quality. They appear pink and have a laser wavelength of 694.3 nanometers.

2. Neodymium-doped yttrium aluminum garnet (Nd:YAG) : Artificial crystal, with a laser wavelength of 1064 nanometers, it belongs to near-infrared light and is completely invisible and unsafe for the eyes. Nd:YAG is currently the most widely used solid-state laser material, far exceeding ruby. The core reason is that its laser threshold is lower, and it can achieve higher output energy under the same input energy.

3. Neodymium-doped yttrium vanadate (Nd:YVO₄) Often simply referred to as “vanadate”, it has become the preferred material for low to medium power (up to several watts) diode-pumped solid-state lasers due to its large stimulated emission cross-section, low laser threshold and polarized output characteristics. The operating wavelengths are 1064 nanometers and 1340 nanometers, and after frequency doubling, it can output lasers with wavelengths of 532 nanometers and 670 nanometers.

4. Neodymium-doped Glass (Nd:Glass) : Using amorphous glass as the matrix, its laser properties are similar to those of Nd:YAG. Its core disadvantage is that its thermal conductivity is relatively low, only 1/10 of that of a crystal, making it difficult to cool in high-power applications. However, its advantage lies in the fact that it can be made into laser media with a diameter exceeding one foot, effectively controlling energy density, avoiding damage to optical components in kilojoule-level pulsed laser, and having a relatively low cost.

Other important solid-state laser materials, erbium-doped materials: including erbium-doped yttrium aluminum garnet (Er:YAG, output wavelength 2940 nanometers) and erbium-doped Glass (Er:Glass, output wavelength 1540 nanometers). Holmium doped materials: including holmium doped yttrium aluminum garnet (Ho:YAG), holmium doped lithium yttrium fluoride (Ho:YLF), and holmium doped Glass (Ho: glass, output wavelength 2000 to 2100 nanometers). Thulium-doped materials: including thulium-doped yttrium aluminum garnet (Tm:YAG), thulium-doped lutetium aluminum garnet (Tm:LuAG), and thulium-holmium co-doped lithium yttrium fluoride (Tm,Ho:YLF, output wavelength 2000 to 2030 nanometers). Ytterbium-doped materials: such as ytterbium-doped potassium gadolinium tungstate (Yb:KGW, output wavelength 1025 to 1045 nanometers). Alexandrite (output wavelength 655 to 815 nanometers). Titanium-doped Sapphire (Ti:Sapphire, output wavelength 840 to 1100 nanometers)