Two Types of Instruments, One Optical Model

How pairing spectroscopic ellipsometry with spectrophotometry produces more reliable optical constants than either technique on its own

If you're designing optical thin-film devices like filters, coatings, or sensors, your designs are only as good as the n and k values you put into them. And here's the problem most engineers run into a model that fits your measurement data isn't necessarily a model that's physically correct.

Spectroscopic ellipsometry is exceptionally sensitive to film thickness and refractive index. But by design, it has a blind spot, one that becomes critical when films scatter light or have low absorption. Without addressing it, your fitting software will confidently return an answer. That answer may describe a structure that doesn't physically exist.
This application note explains what that blind spot is, why it matters, and how adding spectrophotometry to the measurement closes it, giving you an optical model you can trust.

Inside, you'll find:

• Why fitting ellipsometry data alone can produce multiple equally valid (and contradictory) models
• What ellipsometry measures well and what it structurally cannot detect
• A worked example showing the two instruments in combination, including the instruments Covalent uses in-house
• A quick-reference primer on the underlying optics, useful for engineers new to optical characterization

Who this is for: Optical engineers, thin-film process engineers, and device designers who need trustworthy optical constants and want to understand why a combined measurement approach produces them.