Co:Spinel Passive Q-Switch Crystal

22 May 2019

Description

Co spinel——saturable absorbers for the passive Q-switching of solid-state lasers operating at eye-safe wavelength of 1.5 μm

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.

Parameter

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%

Metarial and Specifications

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%