arXiv subjects

Thomas J. Ugras

Publications and source records attributed to Thomas J. Ugras.

2 recordsLinked to original sources

arXiv2026

A Route to Pure Optical Rotation in Self-Assembled Materials through Energetic Non-Degeneracy

Achieving large optical rotation with minimal ellipticity and absorption, 'pure' optical rotation, remains a central challenge in chiral photonics. Solution-processed self-assembled materials can exhibit exceptional chiroptical responses (g-factors > 1), yet their circular birefringence (CB) typically overlaps with circular dichroism (CD) and resonant loss (Absorption), leading to elliptical, attenuated signals. Here, we establish a general, theory-guided design principle showing that non-degeneracy provides a route towards pure optical rotation in self-assembled systems. Using a generalized coupled-oscillator framework, we demonstrate that breaking degeneracy between the excited states of interacting chromophores produces CB in spectral regions where CD and absorption are naturally weak. We experimentally validate this mechanism using mixed assemblies of $α$- and $β$-CdS magic-sized clusters, which exhibit the predicted off-resonant, emergent CB. Guided by this principle, we design a layered architecture that maximizes non-degenerate neighbors through alternating chromophore planes. This structural architecture results in optical response lineshapes optimized for pure rotation. Because the mechanism relies solely on dipolar coupling and energetic detuning, it is generalizable across wavelengths, including in the ultraviolet (~310 nm), where suitable nanocrystal and organic chromophores are readily available. Simulations predict a 50 meV (12 THz) window exhibiting low-dispersion optical rotation of ~20°, >40% transmission, and <1° ellipticity-strong performing benchmarks typically associated with lithographic metamaterials. These results establish non-degenerate coupling as a general mechanism for engineering chiroptical response and provide a strategy for realizing pure optical rotation in self-assembled systems.

physics.optics↗

arXiv2025

Realizing Nonreciprocal Linear Dichroism and Emission from Simple Media

Reciprocity, the principle that a system response is identical in the forward path compared to the backward path, is a fundamental concept across physics, from electrical circuits and optics to acoustics and heat conduction. Nonreciprocity arises when this symmetry is broken, enabling directional-dependent behavior. In photonics, nonreciprocity allows control over the propagation of electromagnetic waves, essential for isolators and circulators. But achieving optical nonreciprocity typically requires complex metamaterials, exotic media, or strong external fields. Because of this, researchers have historically overlooked the possibility that readily available materials could support nonreciprocal optical behavior, assuming that conventional systems lack the ability to produce nonreciprocal behavior. In this work, we challenge that assumption by revisiting the light-matter interactions of chiroptic and linearly anisotropic media. Through Stokes-Mueller formalism we derive a simple analytical expression that predicts a pathway to nonreciprocal absorption and emission of orthogonal linear polarizations. We test this idea experimentally using solution-processed films of CdS, CdSe, and CdTe magic-size clusters that possess commensurate circular dichroism (CD) and linear dichroism (LD)values and find that they can support this effect, engineering films that exhibit nonreciprocal absorption and emission of linearly polarized light. Based on the derived expressions and experiments, several design rules are presented. Our findings reveal that nonreciprocal linear dichroism and emission can be achieved in readily processable, macroscopically symmetric materials by harnessing chiral-linear optical interference. This work opens new opportunities for scalable, polarization-based photonic control for direction-dependent optical routing, optical logic, and polarization-multiplexed information encoding.

cond-mat.mtrl-sci↗