CrY3Al5O12

CrY3Al5O12, commonly referred to as Cr:YAG, is chromium-doped yttrium aluminum garnet. It is a transparent crystalline material used as a solid-state laser gain medium and as a saturable absorber in ultrafast optics. In the YAG host lattice, Cr3+ ions substitute for some Al3+ ions in the octahedral sites, creating active luminescent centers that enable light absorption and infrared emission upon optical pumping.

Crystal structure and composition: Y3Al5O12 is a cubic garnet with a well-defined crystal framework. When doped with Cr3+, the chromium ions introduce energy levels that facilitate absorption in the visible to near-infrared and emission at near-infrared wavelengths, with properties that depend on the local crystal field and doping level.

Optical properties and applications: Cr:YAG exhibits broad absorption bands in the visible region and emits in the near-infrared when excited, typically around 1 μm, making it suitable for laser operation. It is valued for good thermal conductivity, mechanical robustness, and a relatively broad emission bandwidth. Applications include as a solid-state laser gain medium (often pumped by visible diodes) and as a saturable absorber for passive mode-locking of lasers around 1 μm, enabling ultrafast pulse generation.

Synthesis and crystal growth: Cr:YAG crystals are prepared from oxide precursors and grown by crystal growth techniques such as the Czochralski process or flux growth, with chromium incorporated at trace to several percent levels depending on the desired properties.

See also: Yttrium aluminum garnet, Garnet, Cr3+ luminescence.