Are Your “Identical” Optical Components Really Identical?
In the world of optics, pricing is often a key consideration for labs and commercial product developers. Many suppliers offer optical components that appear identical on paper, with similar specifications. However, variations in manufacturing can lead to significant differences in optical surface quality, ultimately impacting their performance.
A recent study, entitled “On the Variation in Surface State of Nominally Identical Fused Silica Optics Surfaces,” investigated these hidden variations. This research highlights how seemingly identical components can exhibit significant performance differences due to surface quality variations.
Classical optics manufacturing involves multiple steps, each with the potential to introduce surface defects and contamination. These defects can be influenced by factors like grinding and polishing techniques, cleanliness and contamination control, necessary lubricants, and polishing agents. The subject of Technical Cleanliness (TC) plays a critical role in optimizing these processes and minimizing surface defects.
This particular study analyzed fused silica samples from four different suppliers, all with seemingly identical properties. Laser-induced breakdown spectroscopy (LIBS) was used to analyze the elemental composition of the samples. LIBS, employed with the CORALIS combined Raman-LIBS system from LTB Lasertechnik Berlin, provides highly precise elemental analysis. (The system also offers complementary Raman spectroscopy for looking at chemical bonds and differences in phase, though not used in this specific study.)
Interestingly, the results revealed significant variations in the optical properties (such as the refractive index) of the samples — properties that theoretically should have been identical. Differences in surface roughness and contamination levels are the likely causes of these variations. This research highlights the importance of considering not just specifications, but also the origin and manufacturing quality of optical components. Surface quality variations can significantly impact performance, potentially leading to costly downstream issues.
About the CORALIS Raman-LIBS System
The CORALIS system unites the two high complementary techniques, LIBS and Raman. By means of a high-quality sample image, pre-selected measurement positions are analyzed either with Raman or LIBS, or with both methods sequentially.
The unique two-wing echelle spectrometer as a core part is able to provide high resolution, large range, and high light-throughput on an unbeatable level. The laser-safe housing and the integrated interlocking circuit ensure user-friendly handling of the device and protection of the installed components.
For more information or a quotation for LTB products, contact IL Photonics.