Elucidating the photophysics behind nonlinear optical phenomena in upconversion systems and two-dimensional materials

Abstract

The study of nonlinear optics has facilitated the development of numerous advanced optical systems. Triplet-triplet annihilation upconversion (TTA–UC) is a nonlinear optical phenomenon that has been exploited widely to design versatile, low-cost frequency upconversion systems. This dissertation presents a deep dive into the kinetics of TTA–UC. A new mass-conserving model designed to fit and extract useful parameters from TTA–UC data is presented, followed by a comprehensive experimental and theoretical study of the major upconversion efficiency loss mechanisms in TTA–UC, and finally a critical analysis of new TTA–UC strategies to upconvert light across the visible spectrum. Additionally, the work presented here explores in detail the nonlinear optical phenomena that arise from the interactions between an emerging group of two-dimensional materials and ultrashort laser pulses. Ultrafast laser ablation is one product of the interaction between 2D materials and ultrashort laser pulses, which is presented in this study as atool for photopatterning these materials and characterizing their nonlinear absorption. A new 2-beam action spectroscopy method is introduced, and is employed to provide mechanistic insights into the ultrafast laser ablation process. The extraordinary waveguiding properties of the wide-bandgap 2D material manganese selenophosphate (MnPSe3) are presented and discussed in detail. Finally, a strategy is presented to use ultrafast laser ablation to create MnPSe3–based nanophotonic devices on demand. This strategy may revolutionize the design and manufacture of future nanooptic devices.