Determining Thin Film Characteristics by Prism Coupling Technique

Abstract

Integrating optical components in a single package to perform a given functionality is now an established procedure when photonic integrated circuits are involved. These photonic integrated circuits may provide wider bandwidth, higher immunity to electromagnetic interference and lower power consumption operation, as opposed to their electronic counterparts, and these features preclude the development of more efficient Information and Communication Technologies devices when both technologies, optical and electronic, are combined for the development of already existing or new devices. Photonic integrated circuits consist of structures such as waveguides, ring resonators, multimode interference sections, and more, laid over a substrate and assembled in a way to perform a given functionality. These structures are usually accomplished through thin film deposition and subsequent lithography, to achieve the intended geometrical form. Characterization of such thin film structures is of utmost importance, being the refractive index and thickness of the structure two of the most relevant structural elements. Usually, these parameters are obtained by ellipsometry which requires a somewhat complex optical setup, generally consisting of a monochromatic light source, a polarizer, a compensator, an analyser, a photodetector and all the associated signals interpret, process and displaying in a human readable form environment, hence representing a significant investment to acquire such a commercially available device. In this work, we present the latest developments we have achieved in a simple experimental optical setup and the associated method developed to accurately determine the refractive index and thickness of thin film wave guiding structures. The refractive index and thickness of the analysed sample were found to be 1.8723 ± 0.0009 and 524.4 ± 1.4 nm, respectively.