Description
Product Introduction：Alexandrite(Cr3+:BeAl2O4) is an excellent broadband tunable laser crystal with a wavelength tuning range of 701-858 nm. It is widely used in dermatology, laser precision processing, remote sensing, atmospheric LiDAR, and medical laser equipment (mainly used for long pulse, Q-switched, and picosecond 755 nm lasers).
The crystal has the advantages of high hardness, high thermal conductivity, high damage threshold, low threshold and high efficiency, and it has excellent thermal shock resistance, which is 5 times higher than that of Nd: YAG.
Table 1. Basic Properties
| Crystal Structure | Orthorhombic |
| Space Group | Pnma |
| Lattice Parameter（Å） | a=5.476，b=9.404，c=4.427 |
| Density | 3.69 g/cm3 |
| Young’s Modulus | 469 GPa |
| Fracture Stress | 0.457-0.948 GPa |
| Mohs Hardness | 8.5 Mohs |
| Melting Point | 1870 ℃ |
| Thermal Conductivity | 23 W/m/K |
| Thermal Diffusion Coefficient | 5.9(//a)，6.1(//b)，6.7(//c) |
| Thermal Shock Resistance | 35-74 W/cm |
| Refractive Index @750 nm | na=1.736，nb=1.741，nc=1.734 |
Tabel 2. Spectral Properties
| Absorption Band | 400-700 nm |
| Emission Band | 710-900 nm |
| Emission Cross-section | 0.7×10-20 cm2 |
| RT Lifetime τ | 262 μs |
Advantages：
Alexandrite is anisotropic, the absorption and gain properties are strongly dependent on the polarization direction of pump light. The crystal has a wide absorption bandwidth and can cover most of the visible light region. Blue, green, yellow, and red light lasers can all be used as pump sources for Alexandrite laser. Different bands of the pump source have different advantages:
1. When blue light is used as the pump source, Alexandrite laser can achieve a broader emission spectrum, which is suitable for ultra-precision material processing that requires a broad-spectrum laser.
2. When yellow or red light is used as the pump source, the laser has high quantum efficiency and is expected to achieve high average power.
3 .The 532 nn green laser beam generated by Nd: YVO4 doubling has good quality and high output power, and is usually the preferred pump source for Kerr lens mode-locked lasers.
Fig 1. Absorption spectra of Alexandrite.
Table 3. Specifications of Alexandrite
| Standard Products | Dia. 5×115 mm；7×110 mm：7×120 mm |
| Dia. 6.35×120 mm；8×130 mm； 9.53×117 mm | |
| Dimension Tolerance | D：+0/-0.05 mm |
| L：+1/-0 mm | |
| Clear Aperture | ＞98% |
| Scratch/Dig | 10/5 |
| Flatness | ＜λ/10 @ 633 nm |
| Parallelism | ＜30″ |
| Perpendicularity | ≦5′ |
| Coating | Normal：AR/AR 755 nm |
| Mirror coating：HR 755 nm/ PR755 nm | |
| Damage Threshold | > 1.5 Million pulses qualified testing by third party |
| Quality Warranty Period | One year under proper use |
Notes：We provide high quality Alexandrite crystals in different sizes, if you have special requirements.
