Thin-film optical anti-reflection coatings are often specified at about 0.1% - 1% transmission loss. For a wavelength-specific V-coating, 0.1% is probably a good estimate. But does anyone know what is the variability in loss from sample to sample? What is the uncertainty on this transmission loss value?
References to published studies or manufacturer spec sheets would be greatly appreciated.
Hi,
First of all, each AR coating is characterized by its reflection, transmission, and absorption. If I understand you correctly, you are reffering to absorption (usually measured in ppm units) as 'trasmission loss'. I think that the anwer to your question highly depends on the specfic coating method that is used (e.g., E-beam, magnetron sputtering, IAD, IBS), the coated element properties (material, surface roughness etc.), and on the exact details of the manufacturing process (such as the type of coating machine and the element location inside the coating chamber).
A good place to start from is reading the following article, which includes measured data of absorption in AR coatings produced using IBS technology:
http://spie.org/Publications/Proceedings/Paper/10.1117/12.905462
If you want to learn more about different coating types, you can read the following tutorial:
http://www.reoinc.com/technical-resources/cat/78/technical_tutorials/article/Coating-Process-Tutorial
I hope it helps,
Assaf
Thank you for the explanation and the references - very much appreciated.
Specifically, I am interested in AR coatings on fiber exit faces. The SPIE Proceedings does a very good job of covering absorption in the thin film coating, including the uncertainty of this value. Absorption is quoted as 0.25 ppm +/- 0.1 ppm, which are very impressive and encouraging values.
I am also interested in the uncertainty of the reflectivity value. This paper - similar to what I have seen on datasheets - quotes reflectivity at 0.1 %. However, the uncertainty of the R value is not stated, and that's what I'm interested in.
I have also found this publication, which talks about measuring the reflectivity with precision of 0.05 %. But I am curious - what kind of precision is possible without calibrating the R value?
http://www.laserfocusworld.com/articles/print/volume-51/issue-10/features/advances-in-optical-manufacturing-measurement-considerations-when-specifying-optical-coatings.html
Hi,
Perhaps you should contact coating compnies, such as Advanced Thin Films (ATF) in order to learn more about their capabilities.
Assaf
Hi, the answers depends mainly on the coating process used, the manufacturer know-how, the design complexity, the coating materials etc... Have a look at this excellent book for more info : http://ebooks.spiedigitallibrary.org/book.aspx?bookid=154.
Thank you for the book reference, Luis. I'll try to track down a copy.
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