Breaking the angular dispersion limit in thin film optics by ultra-strong light-matter coupling

TL;DR

This paper introduces a novel approach using ultra-strong light-matter coupling to create thin film optical filters with minimal angular spectral shift, surpassing traditional limits and enabling advanced photonic applications.

Contribution

The study demonstrates how ultra-strong coupling in microcavities can overcome the fundamental angular dispersion limit in thin film optics, leading to highly stable and tunable optical filters.

Findings

Filters with less than 15 nm spectral shift at extreme angles

Achieved high extinction ratios and up to 98% peak transmission

Realized ultrathin, flexible, and polarization-sensitive filters

Abstract

Thin film interference is integral to modern photonics and optoelectronics, e.g. allowing for precise design of high performance optical filters, efficiency enhancements in photovoltaics and light-emitting devices, as well as the realization of microlasers and high-performance photodetectors. However, interference inevitably leads to a change of spectral characteristics with angle, which is generally undesired and can limit the usefulness of thin-film coatings and devices. Here, we introduce a strategy to overcome this fundamental limit in optics by utilizing and tuning the exciton-polariton modes arising in ultra-strongly coupled microcavities. We demonstrate optical filters with narrow pass bands that shift by less than their half width (<15 nm) even at extreme angles. Our filters cover the entire visible range and surpass comparable metal-dielectric-metal filters in all relevant metrics. By expanding this strategy to strong coupling with the photonic sidebands of dielectric multilayer stacks, we also obtain filters with high extinction ratios and up to 98% peak transmission. Based on these findings, we realize ultrathin and flexible narrowband filter films, monolithically integrate our filters with organic photodiodes, and demonstrate polarization-sensitive polariton filters. These results illustrate how strong coupling provides additional degrees of freedom in thin film optics that will enable a multitude of exciting new applications in micro-optics, sensing, and biophotonics.