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