EUV InsightHow angle changes a Mo/Si mirror
Compare calculated peak reflectivity and wavelength for the same Mo/Si multilayer at different incidence angles measured from the surface normal.
A multilayer optimized at one angle can have a different spectral response at another. Compare the same stack with the illumination changed before changing the layer geometry.
Keep the stack fixed
All comparisons use 40 Mo/Si bilayers on silicon, a 6.9 nm period, and a molybdenum thickness fraction Γ of 0.4. The incident side starts with Si. Mo and Si densities are 10.22 and 2.33 g/cm³. The sweep covers 12.4–14.6 nm in 0.01 nm steps with unpolarized illumination. Angles are measured from the surface normal.
Every interface is smooth in this comparison. Only the incidence angle changes. Peak metrics refer to the sampled band, not all possible wavelengths.
| Angle from normal (°) | Peak reflectivity (%) | Peak wavelength (nm) | R at 13.5 nm (%) |
|---|---|---|---|
| 0 | 73.01 | 13.48 | 72.94 |
| 5 | 72.87 | 13.43 | 71.82 |
| 10 | 72.31 | 13.28 | 48.46 |
| 15 | 71.31 | 13.03 | 12.80 |
Peak reflectivity and reflectivity at 13.5 nm
A mirror can retain a substantial peak reflectivity while its response at your fixed operating wavelength changes. Use the peak-wavelength column to identify spectral movement, and the last column to assess the 13.5 nm operating point.
Reproduce and extend the comparison
Open the default mirror in a Pro workspace. Set the angle to each listed value while keeping the period, fraction and bilayer count fixed. The wavelength × angle map can reveal the response across a wider set of angles.
For polarization-sensitive systems, compare s and p separately. The unpolarized result shown here is an average; it should not stand in for a specified polarized beam.
Check the illuminated angle range
A single-angle calculation describes one plane-wave condition. A finite angular distribution requires an appropriate averaging model; a favorable single point does not establish system throughput.
Calculated examples use the bundled optical reference tables, not measured samples. Zr/Si/Mo example-data fingerprint: 92954053bf1c26ab. Assumptions and data sources.