Alexandrite is a laser active crystal that is widely used in medical and cosmetic applications, such as hair removal and tattoo removal. Alexandrite is a form of chrysoberyl, with a chemical formula of BeAl2O4. It is doped with chromium ions, which allow it to amplify light through stimulated emission.
One of the main advantages of Alexandrite as a laser active crystal is its ability to generate laser emissions at a wavelength of 755 nanometers, which is highly absorbed by melanin, the pigment that gives color to hair and skin. This makes Alexandrite lasers particularly effective for hair removal in people with light to medium skin tones.
Alexandrite lasers are typically pumped by a flashlamp or a diode laser, which excites the chromium ions in the crystal and causes them to emit light at a longer wavelength. Alexandrite lasers can also be mode-locked, which allows them to generate ultra-short pulses in the nanosecond or picosecond range.
Alexandrite lasers have a relatively high conversion efficiency, which means that they can generate high laser powers with relatively low pump powers. They also have good beam quality and can be used for both single-pulse and repetitive-pulse applications.
|Operation in pulsed and CW modes at wavelengths, nm||700 - 820|
|Spatial group||Pnma (D2h16)|
|Lattice space parameters, Å:||a = 5.47; b = 9.39; c = 4.42|
|Refractive indexes||ng = 1.753; nm = 1.747; np = 1.744|
|Thermal conductivity, W x cm-1 x °K-1||0.23|
|Stimulated emission cross-section at 300°K, cm2||3.0 x 10-19|
|Lifetime, sec||260 x 10-6|
|Absorption loss at 750 nm, cm-1||0.001 - 0.003|
|Generation boundaries depending on Cr+3 concentration, J||15 - 30|
|Operation boundaries depending on operation in pulsed and CW mode at wavelengths, µm:||0.70 - 0.82|
Rods with round cross-sections and slabs are manufactured
|Cr dopant concentration, at.%||0.03 ÷ 0.50|
|Diameter, mm||(4 ÷ 10) ± 0.1|
|Length, mm||(60 ÷ 110) ± 0.6|
|Surface quality, scratch/dig||10 - 5|
|Orientation tolerance||< 5°|