Co: spinel crystal, likewise referred to as cobalt spinel, with the chemical formula of Co2+: MgAl2O4. It is a reasonably excellent Q-switched crystal product.

Cobalt spinel is a saturable absorber that can be used for easy Q-switching of solid-state lasers in human eyes. Its secure wavelength is 1.5 μm.

Cobalt-doped magnesium aluminate spinel (Co2+: MgAl2O3) can create brief split second pulses at eye-safe wavelength of 1.5 μm.
The absorption peak of Co: spinel is close to 1520 nm, which is most frequently made use of for eye safety and security laser.