Characterization of optical properties and surface roughness profiles: The Casimir force between real materials

TL;DR

This paper discusses how optical properties and surface roughness of materials influence the Casimir force, emphasizing measurement techniques and correction calculations for high-precision experiments.

Contribution

It provides a comprehensive overview of characterizing optical properties and surface roughness for accurate Casimir force calculations, including practical measurement methods and correction approaches.

Findings

Surface roughness significantly affects the Casimir force at small separations.

Atomic force microscopy effectively characterizes surface roughness for force correction.

Understanding contact distance is crucial for precise force measurements.

Abstract

The Lifshitz theory provides a method to calculate the Casimir force between two flat plates if the frequency dependent dielectric function of the plates is known. In reality any plate is rough and its optical properties are known only to some degree. For high precision experiments the plates must be carefully characterized otherwise the experimental result cannot be compared with the theory or with other experiments. In this chapter we explain why optical properties of interacting materials are important for the Casimir force, how they can be measured, and how one can calculate the force using these properties. The surface roughness can be characterized, for example, with the atomic force microscope images. We introduce the main characteristics of a rough surface that can be extracted from these images, and explain how one can use them to calculate the roughness correction to the force. At small separations this correction becomes large as our experiments show. Finally we discuss the distance upon contact separating two rough surfaces, and explain the importance of this parameter for determination of the absolute separation between bodies.}