(Invited) Advancing Quantitative, Contactless, Non-Destructive Characterization of Photonic and Plasmonic Devices

Non-destructive, contactless, and fast optical spectroscopy and imaging strategies provide great advantages for the modelling and optimization of thin films and nanostructured materials in photonic and optoelectronic applications. In particular, accurate, high-precision determination of the dispersion properties of sub-wavelength materials remains challenging and overlooked despite its massively demonstrated need and benefits to the semiconductor industry. Over the years, our group has used these strategies to study self-assembled nanolasers, hybrid photonic-plasmonic sensors, and photovoltaic devices. To adapt to these challenges we develop a modelling strategy based on Finite-Difference Time-Domain (FDTD) due to its flexibility and generality that makes it suitable to model non-linear and photo-thermal effects. The advantages of FDTD include i) the ability to obtain a wide spectral response from a single time-domain simulation and ii) its capability to model non-periodic structures. Significantly, we demonstrated that quantitative FDTD modelling can achieve sub-monolayer precision thus matching the capabilities of spectroscopic ellipsometry (SE). In turn, SE stands out from other optical techniques because, as a self-referenced and phase sensitive strategy, its demonstrated precision and sensitivity and has been demonstrated in multiple spectral ranges and operation conditions. We will present and discuss the synergic use of the FDTD-SE strategy as a quantitative tool for the characterization of photonic and plasmonic subwavelength structures of interest in optoelectronic, sensing, and energy applications. We gratefully acknowledge the financial support from the RGC (Projects CityU - 11210218, 11219919, 11215121 and 11310122) and ITC (Project ITS/461/18) of HKSAR, China.