Influence of Surface Roughness on Real Contact Measurement using Complex Refractive Index as an Indicator

This report examines the effect of surface roughness on the accuracy of real contact measurement by utilizing complex refractive index. The experimental setup employed ellipsometry to analyze the optical response of a silicon lens pressed against a glass prism. Surface roughness layers were modeled using the effective medium approximation (EMA), and multiple reflections at interfaces were accounted for in the optical analysis. Experimental measurements were compared with theoretical estimates under various surface roughness conditions. The results showed that the measured values of refractive index and extinction coefficient were closer to the model estimates considering both the gap and roughness than to the ones considering only the gap. However, increased roughness introduced significant deviations, revealing the limitations of the current EMA-based model in accurately representing complex rough surface structures.