N & K Extraction from Spectra

If the n & k values of the layer materials used in a process to produce an optical thin film coating are not adequately known, the resulting products will not agree with the designs. This problem can be overcome by depositing a single layer of each of the materials of interest on an appropriately prepared substrate, measuring the spectral results in %T versus wavelength (or wavenumber), and using these spectra to find the n & k values which fit the spectral results. These n & k values can then be used in the designs to better represent what is expected from the deposition process. The process of extracting the n & k values from the spectra is not always easy for every coating operation to perform for themselves, or they may want a second opinion on the n & k values. We offer this service for a reasonable fee per n & k value extraction.

Data Needed for Reasonable Index Extraction

Spectrophotometer Make and Model

100% transmittance (%T) spectrum over the intended range of spectral measurements with no sample in the beam.

0% transmittance spectrum over the range of spectral measurements with an opaque sample in the beam.

%T spectrum over the range of spectral measurements with uncoated substrate in the beam.

%T spectrum over the range of spectral measurements with coated substrate in the beam.

Measured or estimated coating thickness, and how measured or estimated.

Additionally:

Dielectric layers must be thick enough to provide at least 3 extrema (max or min) in the spectral range measured.

Metallic and Cermet layers must also include reflectance (%R) spectra at near normal incidence (<10°) of:

1) the uncoated substrate,
2) no sample (0%R),
3) the %R from the coated side,
and 4) the %R from the uncoated side.
(Such metallic films may not exhibit the extrema of dielectric layers.)

Fee Per Extraction:

One Extraction of n and k represents one layer from the spectra supplied as listed above.

The Introductory Offer to the first ten (10) extractions purchased is: $150 per for a Dielectric layer and $250 per for a Metallic or Cermet layer.

Prepayment in advance is required by Credit Card, Check, or Wire Transfer.



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