Product category:
Coatings and coating systems
News Release from: Laser Components (UK) | Subject: Sputtering technique for laser mirrors
Edited by the Manufacturingtalk Editorial
Team on 15 June 2006
Sputtering technique developed for laser
mirrors
With the continuous and rapid development of new high power lasers requiring higher energy and power density handling, a new sputtering technique has been developed for laser mirrors.
PVD (Physical Vapour Deposition) and IAD (Ion Assisted Deposition) have been offered as standard processes by Laser Components for many years and has earned a respected reputation for quality and performance, in particular for the highest damage thresholds With the continuous and rapid development of new high power lasers requiring higher energy and power density handling, Laser Components has been developing a new sputtering technique for the laser mirrors
This article was originally published on Manufacturingtalk on 1 May 2003 at 8.00am (UK)
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During sputtering, a plasma is produced by an electrical field that drives the coating materials out of a target using one of two methods, DC sputtering, in which the sputtering material is electrically conductive, or RF sputtering, in which a high frequency alternating electrical field is applied to non-conductive materials.
Laser Components offers advice on the best process to use for customers' laser application.
The sputtering process is a very slow process compared to PVD deposition, is more complex and thus more expensive.
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The great advantage of sputtering is the ability to produce a high number of high density coating layers due to the high kinetic energies used to propel coating materials, which is less so for IAD and PVD coatings.
Sputtered coatings are therefore more compact and denser.
The result is that no water can be embedded in the layers (causing cavities), which may lead to lower absorption values.
Thus, the coatings remain stable during laser operation and no shift in the central wavelength occurs.
With fewer cavities there are also fewer flaws, which can, during higher laser power, often be the source of layer destruction.
The layer damage threshold can be decidedly increased, as ISO11254 studies have shown.
Due to the higher coating densities used, different refraction indices are achieved for the layers than with the conventional PVD process, and most significantly, a broader spectral range can be achieved.
For example, OPO and fs-laser mirrors can be manufactured with higher performance than could be achieved before.
A further advantage is the low temperature used during sputtering, which permits the coating of temperature-sensitive materials such as crystals or plastics.
The sputtering process also improves surface cleanliness, resulting in reduced scattering losses and in higher efficiency mirrors.
The substrates are generally coated without a rim or jig lip as the substrates are normally laying on their backs at the bottom of the chamber rather than hanging in holders as in conventional coating chambers.
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