SPONSORED: LASER DAMAGE TESTING Testing matters
Gemma Church explains how and why Belford Research takes a robust and accurate approach to laser damage testing
Different types of laser damage A
ll laser damage tests are not created equal. If you want to accurately determine
how your optics react to laser exposure, you need a robust laser induced damage threshold (LIDT) test.
The ISO standards define laser damage as ‘any permanent laser- radiation-induced change in characteristics of either the substrate or the coating’ where you effectively need to irreversibly break chemical bonds in the test sample. Laser damage tests are
divided into two broad categories. First, there is a pass/fail test, which certifies that a sample can withstand a customer-specified laser fluence. A number of sites across the sample are irradiated, and any laser induced damage constitutes a ‘fail’ result.
Second, there is LIDT
certification. This is the definitive test for a coating, determining the power or energy above which damage is possible. LIDT certification is a more complex process than a pass/fail test – but it’s also more accurate where these tests provide you with more information about your optical component. Dr Rona Belford, CEO at
Belford Research Ltd (BRL), explained: ‘We undertake graphical determination of laser damage thresholds. This method of threshold determination gives additional information from the collated data. ‘For example, the uniformity
of the slope can give information about the quality of the coating process used. An LIDT Certificate issued by BRL contains the full damage pattern, and we are happy
to offer additional post-test consultation on the results.’ BRL also takes a more
robust and tailored approach to its LIDT tests, as Dr Belford added: ‘We don’t provide a turnkey solution. Our staff are all well qualified and highly knowledgeable individuals, who take their time to conduct rigorous testing, tailored to the precise requirements of each customer. We take our time with your optics. Because of this quality of service and the accuracy we deliver, we work with companies across a broad range of sectors, including the medical industry, and military and defence.’ This expertise is vital because the tests themselves can affect the optical component and this can lead to misleading results. Dr Belford explained: ‘My personal view is that you can overtest an optic. You can give it too many shots, and that
changes the sample under test. ‘A lot of electronic defects in
a material can be annealed out,’ she added. ‘So, if you don’t do a stringent test, then a good and a bad sample can come out with the same results, because you’ve changed the sample you’re testing. ‘You’ve effectively rubbed out its defects. We go to great lengths to ensure that does not happen, to ensure the reliability of our tests.’
During a typical LIDT test, an optical component is subjected to laser light. Incident sites, which are usually formed of an array of more than 100 sites, are exposed to the laser beam. Each site is then exposed to several laser pulses. There are usually 10 sites per row, and each row is subjected to the same power level. The number of laser induced
damage incidents per power level is recorded and depicted
BRL carries out laser induced damage threshold testing and certification across the medical and military defence sectors among others 32 Electro Optics March 2021 @electrooptics |
www.electrooptics.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50
