Cr4+:YAG crystal can be used not only as Q-switch but also as gain medium because of its excellent physicochemical properties. The Q-switch operation of pulse and CW Nd:YAG lasers has been realized by using Cr4+:YAG as Q-switch, and the CW tunable and self-mode-locked operation has also been realized by using CR4 +: YAG as gain medium. Compared with the traditional saturable absorber, Cr: YAG is superior to the traditional saturable absorber in many aspects. The doping concentration of Cr4+ ion in Cr4+:YAG is as high as 1018 cm-3, which can effectively reduce the size of passive Q-switch elements. It is beneficial to achieve high optical conversion efficiency, integration, and compact passive Q-switch laser.
Physical and Chemical Properties
| Property | Value |
| Chemical formula | Cr4+:Y3Al5O12 |
| Crystal structure | cubic – la3d |
| Lattice parameters, Å | 12.01 |
| Orientation | [100] or [110] < ±0.5° |
| Mass density | 4.56 g/cm3 |
| Mohs hardness | 8.5 |
| Young’s modulus | 335 GPa |
| Tensile strength | 2 GPa |
| Melting point | 1970°C |
| Thermal conductivity | 0.1213 |
| Specific Heat/ (J·g-1·K-1) | 0.59 |
| Thermal Expansion /(10-6/°C@25°C) | 7.8 <111> 7.7 <110> 8.2 <100> |
| Thermal shock resistance parameter | 800 W/m |
| Extinction Ratio | 25dB |
| Poisson Ratio | 0.25 |
| Refractive Index @1064 nm | 1.83 |
| Charge compensating ion | Ca2+, Mg2+ |
| Property | Value |
| Optical Density | 0.1 to 0.8 |
| Fluorescence lifetime | 3.4μs |
| Concentrations | 0.5 mol % ~ 3 mol % |
| Emission wavelength | 1350 nm ~ 1600 nm |
| Absorption Coefficient | 1.0 cm-1 ～ 7 cm-1 |
| Ground state absorption cross section | 4.3×10-18 cm2 |
| Emission state absorption cross section | 8.2×10-19 cm2 |
| Transmission | 10% to 90% |
| Coatings | AR≤ 0.2% @1064nm |
| Damage Threshold | > 500 MW / cm2 |
| Property | Value |
| 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 | 5ˊ |
| Clear Aperture | >90% |
| Chamfer | <0.1×45° |
| HR coating | <= 0.2% (@ 1340nm) |
| Maximum dimensions | 2*2-15*15 mm×20mm |
Absorption And Transmission Spectrum
High thermal conductivity
High damage threshold(>500MW/cm2)
Excellent physicochemical properties
Radiation stability
Material Processing
Holography
Medical Applications
Passive Q-switch for Nd: YAG laser
Remote sensing
3D scanning
Lidar system