A coating design to rule them all: asymmetric Fabry-Perot resonators with diverse optical response based on Au films with high-temperature sensitivity.

Thermal annealing of thin metal films induces morphology changes that have a dramatic effect in the optical properties. Here we propose an asymmetric Fabry-Perot resonator consisting of a top metal film, a dielectric spacer, and a bottom metal mirror that can display a diverse infrared response. Thermally induced morphology changes result in large reflectivity variations within a limited temperature range following the top film transition between conductive, highly lossy, and transparent regimes. This behavior arises from the combination of the top film properties with interference effects in the multilayer. Furthermore, the proposed structure holds promise for potential sensing applications, as its optical response displays four times larger temperature sensitivity than a single film.

A trusted node-free eight-user metropolitan quantum communication network.

Quantum communication is rapidly gaining popularity due to its high security and technological maturity. However, most implementations are limited to just two communicating parties (users). Quantum communication networks aim to connect a multitude of users. Here, we present a fully connected quantum communication network on a city-wide scale without active switching or trusted nodes. We demonstrate simultaneous and secure connections between all 28 pairings of eight users. Our novel network topology is easily scalable to many users, allows traffic management features, and minimizes the infrastructure as well as the user hardware needed.