Research Area

Magnetic and Optical Systems

Prism Coupler

Prism couplers are used for the fast and accurate determination of refractive index and thickness of transparent thin films. The sample and prism are rotated against the fixed laser beam and the intensity is detected as a function of the angular position. The advantage over conventional ellipsometers is that no previous knowledge of refractive index or coating thickness is required.
Application examples:

  • Measurement of coating thickness and refractive index of coating systems (substrate with coating)
  • Determination of the refractive index of substrates
  • Measurement of doped layers with small refractive index changes

Device configuration:

  • Typical substrate materials include glass, quartz, sapphire, GGG and lithium niobate with wafer diameters of 10 to 200 mm and wafer thicknesses of 0.5 to 5 mm
  • Wavelengths of the lasers: 633 nm and 1550 nm
  • Layer thicknesses: 0.5 to 25 µm (typ.)
  • Refractive index of the layer: 1.0 to 2.5 (TE)
  • Measuring spot: smaller than 1 mm²
  • Automatic calculation of layer thickness and refractive index

Further information can be found at the manufacturer:



Download Prism coupler

Other Measuring Instruments




Model 2010/M

Dr. Carsten Dubs

Team Leader
Crystalline Materials

Phone: +49 3641 282564