Multiwavelength (0.45-10.6 µm) angle-resolved scatterometer or how to extend the optical window.

Area of Science:

• Optics and Photonics
• Materials Science
• Surface Metrology

Background:

• Characterizing surface microroughness is crucial for optical component performance.
• Existing methods may have limitations in wavelength range or spatial resolution.
• Accurate surface topography analysis requires advanced scattering measurement techniques.

Purpose of the Study:

• To describe a novel apparatus for measuring scattered light over a broad wavelength range (0.45-10.6 µm).
• To analyze the performance and limitations of the experimental setup, including parasitic light, calibration, and dynamic range.
• To demonstrate the capability of obtaining bidimensional roughness spectra for polished samples.

Main Methods:

• Development of an apparatus to record scattered light in whole space.
• Utilizing visible and infrared wavelengths (0.45-10.6 µm) for measurements.
• Performing angular measurements at multiple wavelengths to derive roughness spectra.

Main Results:

• The apparatus successfully captures scattered light data across a wide spectral range.
• Bidimensional roughness spectra of polished samples were obtained.
• Overlap in spectra across different bandwidths allowed for an extended view of surface microroughness.
• Challenges in mid-infrared measurements, including thermal emission, were analyzed.

Conclusions:

• The described apparatus is effective for characterizing surface microroughness over a broad wavelength range.
• The method provides detailed topographical information through bidimensional roughness spectra.
• The study highlights the importance of addressing specific challenges for accurate measurements in the mid-infrared spectrum.