Measurement of Reflectivity and Refractive Index Based on Coherence Scanning Interferometry

Coherence Scanning Interferometry (CSI) is widely used in the measurement of the topography and thickness of transparent film. In this letter, a method to reconstruct the reflectivity of samples based on frequency domain analysis of CSI signals is proposed. Compared with conventional spectrometers and hyperspectral image system, this method offers higher lateral resolution. Furthermore, combining the reflection model of film, a method for measuring the refractive index of thick transparent films is also proposed. In the experiments, the reflectivity of a SiO₂ device with gold-plated electrodes and the refractive index of a SiO₂ sample were reconstructed, with relative errors within ±2% of the theoretical reflectivity/refractive index, verifying the accuracy of the proposed method. Using the reconstructed reflectivity and refractive index were employed to calculate the thicknesses of films, yielding results close to those measured by commercial equipment. The proposed method extends the capabilities of CSI.