Using Thin Film Deposition Systems to Create Spherical Anti-Refractive Coatings

Guest is provided by Denton Vacuum, LLC, providing plasma-enhanced chemical vapor deposition sputtering systems for a variety of applications. Visit their website for more details.

Thin Film Deposition Systems allow for coating optics without distorting images. While other methods of anti-reflective coatings can cause a slight adjustment in the image, using a vacuum deposition system prevents this from happening. The films laid on optics from a sputtering system are so thin; they measure at only microns thick. Applications for these results are best used when working with light-sensitive specimen or with telecommunication technology. Using a tightly sealed vacuum sputtering system eliminates the danger of contamination during the thin film layering process.

Using these systems for fiber-to-fiber coupling and fiber collimation in telecommunications was, until recently, accomplished with a graded index (GRIN) lens. Known for being extremely expensive, GRIN lenses are very sensitive to the angle in which they are aligned. Instead of using cylindrically shaped lenses, more professionals are turning to spherical lens, due to its economical value. Spherical lenses are far less expenses and are found to be easier to mount and align.

However, spherical lenses tend to result in a significant reflection loss, which has inhibited its widespread use, in spite of how much cheaper they are to acquire. The refractive index, the amount of light reflected back to the observer, only scores an n = 1.5. If you were to transmit light through four surfaces, you would only receive 85% of its total.  Applying an anti refractive coating (ARC) with a magnetron sputtering system allows for better stability, mechanical integrity and temperature excursions. Studies have shown positive results regarding optical performance, film microstructure, mechanical stability, and in-situ process monitoring.