This is a past event.

Please join physics graduate students, Lucas Simonson and Nithin Allwayin for their in-person presentations on Thursday, March 7th at 4 PM - Fisher Hall 139.

Lucas Simonson (Advisor: Ramy El-Ganainy)

Breakdown of Temporal Coupled Mode Theory Under Multiple Excitations in Microring Resonators

Temporal coupled mode theory (TCMT) is one of the most important tools that are widely used for analyzing and designing integrated photonic systems that consist of multiple connected resonators. In microresonator systems with well-separated modes (relatively large free spectral range compared to the modal width), standard TCMT accounts only for the resonant excitation and is known to give excellent results in the weak coupling limit. In this work, we reveal a peculiar situation where TCMT breaks down under multiple excitation conditions. Our results suggest that while it is safe to use TCMT under a single excitation, it must be applied with care when multiple excitations are involved.

Nithin Allwayin (Advisor: Raymond Shaw)

Observations of Locally Narrow Characteristic Droplet Size Distributions in Stratocumulus Clouds and Their Implications for Cloud Representations

Clouds influence our climate significantly by regulating Earth’s radiation and water balances and their calculations in global climate models (GCMs) rely on an assumed cloud droplet size distribution structure. However, these size distributions are derived from measurements averaged over tens to hundreds of meters and are not representative of cloud structures at small scales, contributing to one of the largest uncertainties in climate predictions. Utilizing a novel ML-clustering algorithm on cm-scale measurements of clouds from the Holographic Detector for Clouds (HOLODEC) made during the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) field campaign, we find that the local cloud size distributions do not resemble these averaged values typical of length scales used in GCMs. Importantly, we find the local size distributions are narrower and tend to occur in regions of similar-looking cloud populations. These observations have significance for calculations of rain initiation and open the way for novel modeling representations of cloud processes.