Alexandrite
Be(Al1-xCrx)2O4
Due to properties such as laser wavelength and tunability, Alexandrite is used in a wide range of medical applications.
Alexandrite lasers emit at a wavelength of 755 nm, well within the absorption spectrum of melanin, and this makes the laser perfectly suitable for removing hair. Alexandrite lasers are also used for a variety of aesthetic dermatology procedures.
Cr concentration uniformity along each rod is achieved by using only a small portion (about 20%) of the melt, with a very uniform Cr profile being certified for each boule.
Optical Properties
| Refractive index@755nm | E II a=1.7367 |
| E II b=1.7421 | |
| E II c=1.7346 | |
| Lasing wavelength | 710 - 800 nm |
| Primary diode pump band | 594 nm |
Material Properties
| Cr doping level | 0.01 - 0.2% atomic |
| Chemical formula | Be(Al1-xCrx)2O4 |
| Molecular weight | 127.01 g/mole |
| Crystal structure | Orthorombic |
| Lattice constant | a=5.476 Å |
| b=9.404 Å | |
| c=4.427 Å | |
| Melting point | 1870 °C |
| Density | 3.67 gr/cm3 |
| Hardness (Mohs) | 8.5 |
Thermal Properties
| Thermal conductivity | 0.23 W/(cm•K) |
| Linear expansion coefficient | II a=5.9 x 10-6/K |
| II b=6.1 x 10-6/K | |
| II c=6.7 x 10-6/K | |
| Dissipative fracture limit | 35-74 W/cm |
| Young modulus | 469 Gpa |
Rod Specifications
| Cr Concentration | |
| Concentration | Available from 0.1 to 0.2% |
| Dimensional tolerance | |
| Diameter | +0.00 / -0.05 mm |
| Length | +0.25 / -0.00 mm |
| Chamfer | |
| Depth | 0.02±0.01 mm |
| Angle | 45°±5° |
| End Configuration | |
| Parallelism | <10" |
| Perpendicularity | <2' |
| End angle tolerance | ±10' |
| End Surface Finish | |
| Flatness | < λ /10 at 633 nm |
| Scratch-dig (as per MIL-I-13830A) | 10 – 5 |
| Wavefront distortion | |
| Per inch of rod length | < λ /2 at 633 nm |
| Standard coating specification | |
| Anti-reflection | <0.2% |
| Traceability | |
| Laser marking | Lot number on rod external surface |