Residual surface roughness of diamond-turned optics

Area of Science:

• Optics and Materials Science
• Surface Metrology

Background:

• Diamond-turned optical surfaces often exhibit periodic roughness.
• Understanding this roughness is crucial for predicting optical performance.

Purpose of the Study:

• To explore the optical properties of surfaces with periodic roughness.
• To apply Rayleigh-Rice vector scattering theory to this specific case.
• To provide methods for interpreting optical measurements of such surfaces.

Main Methods:

• Application of Rayleigh-Rice vector scattering theory for periodic roughness.
• Derivation of expressions for analyzing scatter, reflectometry, and ellipsometry data.
• Consideration of the limit of highly conducting surfaces.

Main Results:

• Optical measurements can reveal information about the 2D power spectral density of surface roughness.
• The nominal range of information extends from the wavelength of light to the beam spot diameter.
• Differential-scatter, total-integrated-scatter, reflectometry, and ellipsometry are explored.

Conclusions:

• Optical characterization techniques are effective for analyzing periodic surface roughness in optics.
• The derived expressions aid in interpreting measurements for practical mirror surface characterization.