Co:Spinel

Passive Q-switches or saturable absorbers generate high power laser pulses without the use of electro-optic Q-switches, thereby reducing the package size and eliminating a high voltage power supply. Co2+:MgAl2O4 is a relatively new material for passive Q-switching in lasers emitting from 1.2 to 1.6μm, in particular, for eye-safe 1.54μm Er:glass laser, but also works at 1.44μm and 1.34μm laser wavelengths. Spinel is a hard, stable crystal that polishes well. Cobalt substitutes readily for magnesium in the Spinel host without the need for additional charge compensation ions. High absorption cross section (3.5×10-19 cm2) permits Q-switching of Er:glass laser without intracavity focusing both with flash-lamp and diode laser pumping. Negligible excited-state absorption results in high contrast ratio of Q-switch, i.e. the ratio of initial (small signal) to saturated absorption is higher than 10.

Basic Properties:

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
Specific Heat/ (J·g-1·K-1)
1.046
Thermal Expansion /(10-6 /°C@25°C )
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%
Absorption coefficient
0 ~ 7 cm-1
Working wavelength
1200 – 1600 nm
Coatings
AR/AR@1540,R<0.2%; AR/AR@1340,R<0.2%

Technical Parameters:

Orientation Tolerence
< 0.5°
Thickness/Diameter Tolerance
±0.05 mm
Surface Flatness
<λ/8@632 nm
Wavefront Distortion
<λ/4@632 nm
Surface Quality
10/5
Parallel
10〞
Perpendicular

Clear Aperture
>90%
Chamfer
<0.1×45°
Maximum dimensions
Dia(3-15)×(3-50)mm