Challenging the fundamental limit of angular dispersion by hybridizing light and matter

Project Information

HyAngle

Grant agreement ID: 101097878

DOI

10.3030/101097878

EC signature date 14 June 2023

Start date 1 December 2023

End date 30 November 2028

Funded under

• European Research Council (ERC)

Total cost

€ 2 500 000,00

EU contribution

€ 2 500 000,00

Coordinated by

UNIVERSITAT ZU KOLN
Germany

Periodic Reporting for period 1 - HyAngle (Challenging the fundamental limit of angular dispersion by hybridizing light and matter)

Reporting period: 2023-12-01 to 2026-05-31

Summary of the context and overall objectives of the project

Interference is one of the most fundamental phenomena in optics, allowing scientists and optical engineers to confine, filter, manipulate and steer light with exquisite precision. It is at the core of thin-film optics and nanophotonics, two areas of science that catalyse major scientific and industrial advances. One fundamental property of optical interference, however, constitutes a major limitation – the characteristics of any interference-based structure depend on the angle between the light wave and the structure itself (e.g. the transmission wavelength of optical interference filters shifts strongly when the angle of incidence changes). So far, this ‘angular dispersion’ effect remains a largely unchallenged fundamental limit in optics.
HyAngle proposes a novel strategy based on hybridizing light and matter states to break this angular dispersion limit. By tuning the coupling strength and offset between a photonic resonance formed by optical interference and the electronic resonance causing optical absorption in a material, the researchers on this project work to realize interference-based optical devices with spectrally sharp and angle-independent transmission, reflection and emission.
The project explores the physics, potential and limitations of this approach by developing and studying dispersion-free optical filters, colour converters and LEDs with narrowband spectra. It will then pursue two specific applications, namely hyperspectral cameras and bio-implantable lensless fluorescence microscopes, where it is expected that the devices will enable major advances in capability and unprecedented performance in deep tissue applications.
The devices developed in this project use organic materials that can be readily processed by high-throughput vacuum deposition and even from solution. The amorphous nature of these materials renders them intrinsically compatible with the dielectric and metallic films widely used in the optics and display industry. The strategy of HyAngle thus bears great potential for rapid development and broad application.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The HyAngle project explores the physics, potential, and limitations of polariton-mediated dispersion management by developing and studying three basic devices. Each of these is associated with a work package:
WP 1: non-dispersive optical filters,
WP 2: [confidential]
WP 3: efficient polariton LEDs with narrowband and angle-independent spectra.

Based on the insights obtained during the above activity, the project pursues two specific applications where the above devices enable major advances in capability. Each of these applications is associated with a further work package:
WP 4: hyperspectral imaging with high numerical aperture optics and
WP 5: lensless imaging of hyperspectral and fluorescent signals.

In addition, an underpinning workpackage (WP #0) is dedicated to gathering and organizing information relevant to the project as a whole, in particular information on specific material properties, processing methodology and device characteristics.

While progress in the first reporting period has been delayed due to larger than expected challenges with recruitment of suitable team members, some activity has taken place on all workpages, with the exception of WP #4 (which is only scheduled to start in M31). Activities on all workpackages are ongoing. Specifically, following a literature research on suitable organic materials, a range of materials has been characterized in further detail (in particular via ellipsometry), and their properties are now being catalogued (WP #0). A series of filters has been developed, fabricated and tested (WP #1, Nature Communications 10.1038/s41467-024-54623-1). Planning has taken place to identify this materials and designs required for the devices made in WP #2. Relatively extensive work on WP #3, including optical modelling and fabrication and characterization of a series of test devices has led to the demonstration of a new record in the performance of polariton LEDs as well as to a series of polariton LEDs and lasers (ACS Photonics acsphotonics.3c01610; MRS Communications 10.1557/s43579-024-00543-6). Given the promising results in WP #1, initial work is underway on WP #5, even though the original start of this WP was only planned for M31.

The main achievement during the first reporting period is the improvement in polariton LED efficiency. A publication on this work is currently under external peer review.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

A main result beyond the state of the art in the first reporting period is the improvement of polariton LEDs. This was achieved by combining a highly efficient but intrinsically broadband emitter material that is widely studied in current research on OLEDs (organic LEDs) with a strongly absorbing assistant strong coupling material in a modified microcavity structure. Through optimizing the assistant strong coupling layer architecture, polariton OLEDs with exceptionally narrowband, angle stable emission at external quantum efficiencies above 20% were demonstrated for both bottom- and top-emitting designs (with the latter being of particular relevance for the display industry). This result more than doubles the performance of previous record devices. These results pave the way for utilizing polaritonic emission at practical device efficiencies for display applications.

Given the practical relevance of the science underpinning HyAngle turns out to be significant, the PI has formed a team to pursue translation into a spin-out company. Here the focus is on optical filters rather than LEDs at present. Different aspects of this activity are supported by PoC funding as well as through a German government project (EXIST). While this is highly promising, it becomes clear that important aspects of the underpinning science remain incompletely understood. Both from an academic viewpoint and to safeguard long-term commercial success, it is therefore crucial to continue the structured basic research into the fundamental limits of angular dispersion that is pursued in the HyAngle project.