Investigations of Strong Light-Matter Interactions in Nanophotonic Systems
Doctoral thesis, 2019

Noble metal nanoparticles can support localized surface plasmon resonances (LSPR), thus behaving as open optical resonators. Outstanding optical properties as well as a subwavelength mode volume make plasmonic nanoparticles a promising platform for enhanced light-matter interactions. Light is focused to a nanoscale volume, so called ‘hot-spots’, resulting in strong electromagnetic field amplification in that region. An emitter placed in such a hot-spot can couple with the LSPR of the nanoparticle and thereby experience a dramatic change in its properties.
When the light-matter interaction becomes strong enough, the system enters a special regime, so-called strong coupling. In this regime, the cavity and emitter exchange their energy in a coherent manner on time scales that are faster than their respective dissipation rates. This leads to the formation of new hybrid light-matter states, referred to as polaritons. In this strong light-matter coupling regime, not only the optical but also material-related properties of the system can be modified.
The aim of this thesis is to show and discuss room temperature strong light-matter coupling as well as beneficial and limiting factors of the coupling process. Excitons in transition metal dichalcogenides (TMDC) are coupled to plasmonic resonances of individual gold nanobipyramids (BPs). Strong coupling of excitons and BPs in a single hot-spot is demonstrated. Subsequentially, the asymmetric photoluminescence (PL) emission behavior of this hybrid system is investigated and discussed. Moreover, an interesting case of strong coupling arises when the TMDC material itself is made thick enough to support resonant Fabry-Pérot optical modes in the same frequency range as the exciton resonance. In such circumstances the excitons can be self-hybridized with the optical resonator made of the same material and thereby modify the absorption of the TMDC material over the whole visible spectrum.
In addition to the above-mentioned studies of strong coupling, nonlinear laser microscopy has been employed to study plasmonic, as well as biological samples. And finally, the effect of temporal PL coherence from a single plasmonic nanoparticle is demonstrated as well as different methods for sample analysis and understanding their limitations are discussed.


strong coupling

localized surface plasmon resonance


PJ lecture hall
Opponent: Nicolas Stenger, DTU Fotonik, Denmark


Michael Stührenberg

Chalmers, Physics, Bionanophotonics

Seeing is believing. Being able to see is crucial for understanding our environment. Light is detected by our eyes and converted into electric signals. These signals travel to the brain, where this information is interpreted as color and shapes. This is just one example of the interaction between light and matter. In general, light-matter interactions take place on all different length-scales from whole planets down to a single atom. The strength of a light-matter interaction can have a dramatical impact on the optical as well as material related properties of the interacting system. For instance, gold in a bulk form has a specific yellowish shiny color. However, a tiny gold particle at the nanoscale can appear in red, blue, green, or any other color over the whole visible spectrum of light, depending on the size and shape of the particle, and the refractive index of its surrounding medium. The reason for this is a strong light-matter interaction, called plasmon polariton. This results in a huge modification of the particles optical properties, such as which color of light is reflected and which is absorbed. One of the earliest examples of such a plasmonic effect is the 4th century Roman Lycurgus cup. The color of the cup depends on if a light-source is in front or behind the cup. In reflection the cup appears to be green, while looking at light transmitted through the cup it appears to be red.
In modern science, strong light-matter interactions or strong coupling, is very attractive due to its ability to merge different fields of physics, namely quantum optics and material science. Furthermore, many interesting effects in quantum physics require cooling to temperatures below -200 degree Celsius, whereas strong coupling could make them accessible at ambient conditions.
This thesis aims to contribute in a better understanding of single plasmonic nanoparticle strong coupling with excitonic materials at ambient conditions.

Subject Categories

Atom and Molecular Physics and Optics

Other Physics Topics

Condensed Matter Physics



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4613


Chalmers University of Technology

PJ lecture hall

Opponent: Nicolas Stenger, DTU Fotonik, Denmark

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