Diffuse reflecting surfaces for the infrared and far infrared.

Area of Science:

• Materials Science
• Optics
• Surface Engineering

Background:

• Developing efficient random-scattering surfaces is crucial for advanced optical applications.
• Existing surfaces often lack the required reflectivity and diffusion uniformity in the infrared spectrum.

Purpose of the Study:

• To fabricate and characterize efficient random-scattering surfaces for infrared (IR) applications.
• To achieve high net reflectivity and uniform diffusion for use in resonator cavities and other optical systems.

Main Methods:

• Submillimeter-sized shavings or pellets were cemented to a metallic substrate using metal-filled epoxy.
• A silver (Ag) overcoating was deposited onto the prepared surfaces.
• Surface height and lateral spacing distributions were measured, showing near-Gaussian profiles.
• Net surface reflectivity and three-dimensional angular intensity distributions were measured at various IR wavelengths.

Main Results:

• Achieved net surface reflectivities of ≥90% at 10 µm.
• Angular intensity distributions closely matched the cosine law for uniform diffusion (within ~10%).
• Extrapolated data and measurements at 90 and 250 µm indicate >96% reflectivity for wavelengths ≥90 µm.
• Demonstrated control over scattering element dimensions.

Conclusions:

• The fabricated surfaces offer high reflectivity and uniform diffusion in the IR and far-IR spectrum.
• These surfaces are suitable for overmoded resonator cavities used with tunable, pulsed, far-IR lasers.
• The surfaces have potential applications in other areas requiring high reflectivity, uniform diffusion, and controllable scattering element dimensions.