Professor Guillermo Pedro Acuna, Department of Physics, University of Fribourg, Switzerland

Towards accessible extreme fluorescence sensing and single photon chiral emission

In this presentation, we will focus on the main developments in our lab related to extreme sensing and chirality. First, we present a novel, low-cost, portable smartphone-based fluorescence microscope capable of directly detecting single molecules without signal amplification. The setup leverages the image sensors and data handling capacity of mass-produced smartphones, making it adaptable to any smartphone and capable of detecting single molecules across the visible spectral range. We showcase this capability through single-molecule measurements on DNA origami models and super-resolution microscopy of biological cells by single-molecule localization microscopy. This development paves the way for biotechnology innovations making use of massively distributed or personalized assays with single-molecule sensitivity with the potential to revolutionize digital bioassays, point-of-care diagnostics, field expeditions, STEM outreach, and life science education.

In the realm of chirality, the helicity of photons, akin to the spins of electrons, holds promise for encoding information swiftly through the polarization of light in both classical and quantum computing. However, the development of a chiral single photon source remains a significant challenge due to the degeneracy of magnetic sublevels in achiral emitters. Here, we demonstrate the achievement of chiral single-photon sources made by a DNA templated trimer antenna with C2v symmetry group, excited by an asymmetrically positioned achiral emitter without vector beam excitation. In this 2D configuration without inherent structural chirality, the antenna still exhibits chiral emission with a high degree of circular polarization (DCP), attributed to the presence of excited rotating orthogonal electric dipoles inside the structure.