ALEXANDRITE

Rod standard variable specifications

Cr doping : 0.1 – 0.2 %
Diameter : 2 – 12 (± 0.025 mm)
Lenght : 5 – 150   (+1.0 mm / -0.5 mm)
Parallelism : < 10 arc sec
Perpendicularity : < 5 arc minute
Chamfer : 0.1 – 0.2 mm ± 0.05   @45° ± 5°
Flatness : < λ/10 @633nm
Scratch/dig : 10 – 5
Wavefront deformation (per inch @633 nm) : < 0.5 λ
Extinct ratio : > 25dB @633nm
Traceability :  S/N on cylindrical surface
Reflection coating :
AR @755 nm, R <0.25% (single-layer MgF2) ;
BBAR @710-830 nm (multi-layer) ;
Mirror HR @755 nm, R > 99.8% ;
Partially Reflective coatings (e.g. PR81.5% @755 nm).
Other special custom coatings are also available.

PHYSICAL PROPERTIES

Cr doping level :  0.1 – 0.2 %
Chemical formula :  Be (Al1-x Crx )2 O4
Primary diode pump band :  594 nm
Molecular weight :  127.01 g/mole
Crystal structure :  Orthorhombic
Lattice constants:
a = 5.476 Å   b = 9.404 Å   c = 4.427 Å
Melting point :  1870 °C
Density :  3.67 g/cm3
Mohs hardness :  8.5 @ 20 °C

OPTICAL PROPERTIES
Reflective index (n):
E || a: n(a) = 1.7367
E || b: n(b) = 1.7421
E || c: n(c) = 1.7346
Lasing wavelengths (λ) : 710-800 nm
Primary diode pump band : 594 nm

THERMAL PROPERTIES
Thermal conductivity : 0.23 W/(cm•K)
Specific heat : 0.59 J/(g•K)
Linear expansion coefficient:
||a: 5.9×10-6/ K
||b: 6.1×10-6/ K
||c: 6.7×10-6/ K
Dissipative fracture limit : 35 – 74 W/cm
Young modulus : 469 GPa

Alexandrite, among the solid-state laser crystals, is the most appropriate for a wide range of medical applications due to its physical properties, such as the lasing wavelength and tunability. Indeed, alexandrite is the first of a class of tunable solid-state laser materials. It features a broad tuning wavelength range, 710 – 800 nm, with capability to store and efficiently extract multi-J energy pulses.
It is one of the most robust solid-state laser materials available with a thermal shock resistance five-times that of Nd:YAG.

It offers applications in dermatology, lithotripsy, dental, spectrosocopy, atmospheric LIDAR, testing of fiber optics and photodetectors, materials processing, pumping of dye lasers, non-linear optics studies and annealing of semiconductors.

Alexandrite lasers emit at a wavelength of 755 nm, that is well within the absorption spectrum of melanin in the skin, resulting in hypopigmentation, and enabling the use of these lasers for treatment of pigmented lesion, such as removal of green/blue/black tattoos, brown pigment spots, lentigines and age spots. It’s also used in hair removal and leg vein reduction.

Ultra-pure gas and superior raw material purity, together with a securely controlled proprietary process, allow FILAR OptoMaterials to proudly offer premium grade Alexandrite crystal rods with low losses and higher efficiency.
Chromium concentration uniformity, along each rod, is achieved by using only a small portion (about 20%) of the melt. A very uniform Chromium profile is certified for each boule, that is also marked for identification.

In-house coating allows a short cycle time after end polishing, assuring high adherence and contamination-free layers.

alexandrite discs and 1 cent
Alexandrite slabs
Alexandrite boule
alexandrite absorption spectrum
Alexandrite reflectance with AR coating at 755 nm
Alexandrite reflectance with HR and PR coatings