Cobalt-doped magnesium aluminate spinel (Co:MgAl2O4) allow the generation of short nanosecond pulse with high peak power around the eye-safe wavelength of 1.5um,perfect for telemetry applications. The absorption spectrum of Co2+-doped MgAl2O4 exhibited a broad absorption band in the wavelength range of 1200–1600 nm, which indicated that Co2+ ions substituted for the tetrahedrally coordinated Mg2+ ions in the MgAl2O4 lattice. Passive Q-switching of solid-state lasers with solid-state saturable absorbers is a very attractive Q-switching technique because it allows to develop compact and low cost laser sources of nano and sub nanosecond pulses far various applications.
Lasers emitting at 1.5µm are of great interest for several industrial applications. This interest is, first of all, due to eye-safety of 1.5-µm radiation. Other advantages of this wavelength are high transparency in atmosphere and fused-silica wave guides and availability of sensitive room temperature light detectors(Ge and InGaAs photo diodes).All this makes 1.5µm lasers very attractive for applications in range-finder, environmental sensing, telecommunications, surgery,etc. Co：Spinel absorption peak is close to 1520nm,which is most used in eye-safe laser. The absorption cross-section at 1520nm is 3.5×10-19cm2 and at 1331 is 2.8×10-19cm2,it has reported as Q-switch crystal for Er,Yb Glass and Nd:GYSGG,Nd:YALO3.
Physical and Chemical Properties
| Property | Value |
| Chemical formula | Co2+:MgAl2O4 |
| Crystal structure | Cubic |
| Lattice parameters | 8.07Å |
| Density | 3.62 g/cm3 |
| Melting Point | 2105°C |
| Refractive Index | n=1.6948 @1.54 μm |
| Thermal Conductivity/(W·cm-1·K-1@25°C) | 0.033W |
| Thermal Expansion /（10-6 /°C@25°C ） | 1.046 |
| Specific Heat/ (J·g-1·K-1) | 5.9 |
| Hardness (Mohs) | 8.2 |
| Extinction Ratio | 25dB |
| Orientation | [100] or [111] < ±0.5° |
| Optical density | 0.1-0.9 |
| Damage Threshold | >500 MW/cm2 |
| Doping concentration of Co2+ | 0.01-0.3 atm% |
| Property | Value |
| Concentrations | (0.05~0.35) wt% |
| Absorption coefficient | 0 ～ 7 cm-1 |
| Ground-state absorption cross-section GSA(E-19 cm2) | 2.8（±0.4）@1340nm |
| Excited state absorption cross-section ESA(E-20 cm2) | 2.0（±0.6）@1340nm |
| Ground-state absorption cross-section GSA(E-20 cm2) | 3.5（±0.4）@1540nm |
| Excited state absorption cross-section ESA(E-20 cm2) | 1.0（±0.6）@1540nm |
| Working wavelength | 1200 – 1600 nm |
| End Configuration | Flat/Flat |
| Figure of Merit(FOM) | 100~300 |
| Coatings | AR/AR@1540，R<0.2%; AR/AR@1340，R<0.2% |
Rare excited absorption
High constant of Q-switch
High absorption section
Long excited lifetime
Evenly distributed cobalt
Wide absorption band
Radar and Ranging
Medical Applications