Fraunhofer Institute for Reliability and Microintegration IZM
Fraunhofer Institute for Reliability and Microintegration IZM

Testing, Qualification, Reliability

Refractive index

Mode spectroscopy and RNF for highly precise characterization of refractive index of materials and components

Metricon
Metricon

Mode spectroscopy

Mode spectroscopy is a highly precise possibility to determine the thickness of a dielectrical layer as well as its refractive index. The procedure is based on the total reflection at boundary layers with different refractive indices.

Polar-Plot (LCP- Material)
Polar-Plot (LCP- Material)
  • No information about thickness required
  • High accuracy for measurements on volume- or layer samples
  • TE/TM-mode
  • 3 wavelengths: 633 nm, 830 nm and 1550 nm
  • Extrapolation of the dispersion relation
  • Measurement of anisotropic materials (refractive index distribution TM/TE-mode

Accuracy refractive index: ± 0.001Resolution refractive index: ± 0.0005
Accuracy thickness: ± 0.5%
Resolution thickness: ± 0.3%
Refractive index up to 2.45 (2.7)

graphic - Two dimensional refractive index plot of polymer waveguide foil with 50 µm x 50 µm core and cladding
Two dimensional refractive index plot of polymer waveguide foil with 50 µm x 50 µm core and cladding

Refractive-Near-Field-Method

By scanning the near field with special devices, a 2-dimensional profile of the refractive index distribution can be produced (Refractive-Near-field-method, RNF). This enables the characterization of wave guide structures in polymer and silica on silicon, fibers and gradient profiles as well as diffractive optics.

  • Range of refractive indices: n = 1.42 - 1.62
  • Resolution of refractive index: 1*10-4 absolute value
  • Scanning range: 400x400 µm
  • Local resolution of refractive index: 0.5 µm (670 nm)
  • Light source: Diode laser 670 nm