Flowtube Material Selection

Clear Fused Quartz

Clear Fused Quartz is a relatively low cost material with a wide spectral transmission and high power handling capability.

It has a spectral transmission down to 200nm and is therefore never used when there is a requirement to block the UV output of the lamp to prevent damage to the laser system components.

Clear Fused Quartz is also prone to solarisation  the pale pink discolouration caused by the reaction of UV with certain naturally occurring impurities in the quartz.

Cerium Doped Quartz

Cerium Doped Quartz is Clear Fused Quartz which has been doped with Cerium Oxide. This doping causes the material to block all

 
wavelengths below 382nm and therefore cuts off all of the UV output from the lamp - preventing UV damage to the laser system components. Because the UV is blocked, Cerium Doped Quartz is also less prone to Solarisation.
The UV absorption of Cerium Doped Quartz causes it to fluoresce in the visible spectrum. Some of this fluorescence can be absorbed by the laser rod and can cause a slight increase in laser pumping efficiency.
Flowtubes manufactured from Cerium Doped Quartz are typically four times the price of an equivalent flowtube made from Clear Fused Quartz.

Titanium Doped Quartz

Titanium Doped Quartz is Clear Fused Quartz which has been doped with Titanium Oxide.
This doping causes the material to block all wavelengths below 235nm and therefore cuts off some of the UV output from the lamp.
This material still emits some UV wavelengths and consequently does not prevent damage to laser system components to the same extent as Cerium Doped Quartz. Titanium Doped Quartz does not fluoresce and can suffer from Solarisation.
Consequently, Titanium Doped Quartz is rarely used in flowtube applications and its use is usually limited to air cooled lamp applications where ozone creation needs to be prevented.

Pyrex

Pyrex has many advantages for flowtube applications. Pyrex blocks all wavelengths below 300nm and so has similar spectral limiting properties to Cerium Doped Quartz. It does not fluoresce and therefore does not improve lamp pumping efficiency. It is a low cost alternative though as it has a similer cost to Clear Fused Quartz.
Our Pyrex flowtubes also have an additional annealing process to relieve the stresses induced during the manufacturing process  this is not necessary when working Quartz but is essential with Pyrex.