Tamm plasmon polariton in planar structures: A brief overview and applications

Tamm plasmon provides a new avenue in plasmonics of interface states in planar multilayer structures due to its strong light matter interaction. This article reviews the research and development in Tamm plasmon polariton excited at the interface of a metal and a distributed Bragg reflector. Tamm plasmon offers an easy planar solution compared to patterned surface plasmon devices with huge field enhancement at the interface and does not require of any phase matching method for its excitation. The ease of depositing multilayer thin film stacks, direct optical excitation, and high-Q modes make Tamm plasmons an attractive field of research with potential practical applications. The basic properties of the Tamm plasmon modes including its dispersion, effect of different plasmon active metals, coupling with other resonant modes and their polarization splitting, and tunability of Tamm plasmon coupled hybrid modes under externally applied stimuli have been discussed. The application of Tamm plasmon modes in lasers, hot electron photodetectors, perfect absorbers, thermal emitters, light emitting devices, and sensors have also been discussed in detail. This review covers all the major advancements in this field over the last fifteen years with special emphasis on the application part

Topological engineering of interfacial optical Tamm states for highly-sensitive near-singular-phase optical detection

We developed planar multilayered photonic-plasmonic structures, which support topologically protected optical states on the interface between metal and dielectric materials, known as optical Tamm states. Coupling of incident light to the Tamm states can result in perfect absorption within one of several narrow frequency bands, which is accompanied by a singular behavior of the phase of electromagnetic field. In the case of near-perfect absorptance, very fast local variation of the phase can still be engineered. In this work, we theoretically and experimentally demonstrate how these drastic phase changes can improve sensitivity of optical sensors. A planar Tamm absorber was fabricated and used to demonstrate remote near-singular-phase temperature sensing with an over an order of magnitude improvement in sensor sensitivity and over two orders of magnitude improvement in the figure of merit over the standard approach of measuring shifts of resonant features in the reflectance spectra of the same absorber. Our experimentally demonstrated phase-to-amplitude detection sensitivity improvement nearly doubles that of state-of-the-art nano-patterned plasmonic singular-phase detectors, with further improvements possible via more precise fabrication. Tamm perfect absorbers form the basis for robust planar sensing platforms with tunable spectral characteristics, which do not rely on low-throughput nano-patterning techniques.Comment: 31 pages; 6 main text figures and 10 supplementary figure

Light matter interaction in hybrid plasmonic/photonic nanogaps

The aim of this thesis is to study the processes of light matter interaction at the nanoscale in hybrid nano gaps that are made from both metals and dielectrics. This approach enables the possibility to use both the optical properties of a dielectric, such as low losses and high-quality factor, with the small mode volume typical of a metal. High quality factor and small modal volume together make a high Purcell factor, which is the enhancement of the spontaneous emission rate due to the surrounding cavity environment. Both the size and the time scales involved in this study range in the nanometre and nano second, respectively.The architecture used for the study of the hybrid nano gaps consists of a substrate containing a Distributed Bragg Reflector (DBR) and a 10 nm thick emitting layer. On top of this layer lies a small concentration of gold nano spheres. Two different emitting dipole orientations have been studied, vertical and horizontal. The vertical orientation is parallel to the nano gap dipole moment while in the case of the horizontal orientation, it is perpendicular to it. These two emitting dipole orientations have been used to perform two different experiments exploiting different properties of the DBR. DBRs have been used for two purposes, reflectors and 1-d photonic crystals. These two applications are used to investigate different properties of the hybrid nano gaps. Indeed, DBRs have a highly reflective spectral region called photonic stopband, outside of it there are some highly localised reflectivity minima called Bragg modes.The first hybrid nano gap application explored is the directional nano antenna. In this approach the DBR is used as a reflector and the nano cavity is used to control the direction of the emission. Because of the Fermi golden rule, the dipole moment of the emitter and the nano gap must be parallel to achieve the largest coupling possible. The dipole orientation parallel to the cavity dipole moment is called vertical and it has been probed using the emitter Lumogen Red. This dye exhibits a high quantum yield, low photo bleaching and a good vertical orientability when spun on a surface in form of a film. In this configuration, the light is emitted by the layer at very large angle compared to the surface, roughly 60 degrees. The system can measure up to 64 degrees since the objective numerical aperture is 0.9/1. In this nanogap the nanoparticle acts like a directional antenna and 65% of the emitted light gets redirected at angles not accessible by emitters on their own. Spectrally dispersed k-space imaging has been used to perform such a measurement. This study has demonstrated how the light emission cone is a function of the nano particle size. The narrowest emission cone observed was found to occur for a 500 nm diameter particle size. This configuration showed an enhancement emission factor ranging from 30 up to 60.The second nano gap configuration used the DBR as photonic crystal to achieve localised Tamm plasmon generation. These results are described in chapter 6. The minimum in the reflectivity spectrum of the DBR is called the 1st Bragg mode. In this mode the impinging radiation can penetrate inside the stack and not propagate outside. Tamm states are surface states that can be excited at the interface between a DBR stack and a metal film. Super Tamm are more localised Tamm states that can be excited only by replacing the metallic film with a finite structure such as a micro disk. In this thesis, a new form of localised super Tamm states has been excited. This novelty state has been named Isolated super Tamm modes. The disk has been replaced with a gold nano sphere. Isolated super Tamm modes have been proved to have an intermediate spectral position between the 1st Bragg mode and the super Tamm

Hybrid 1D Plasmonic/Photonic Crystals are Responsive to Escherichia Coli

Photonic crystal-based biosensors hold great promise as valid and low-cost devices for real-time monitoring of a variety of biotargets. Given the high processability and easiness of read-out even for unskilled operators, these systems can be highly appealing for the detection of bacterial contaminants in food and water. Here, we propose a novel hybrid plasmonic/photonic device that is responsive to Escherichia coli, which is one of the most hazardous pathogenic bacterium. Our system consists of a thin layer of silver, a metal that exhibits both a plasmonic behavior and a well-known biocidal activity, on top of a solution processed 1D photonic crystal. We attribute the bio-responsivity to the modification of the dielectric properties of the silver film upon bacterial contamination, an effect that likely stems from the formation of polarization charges at the Ag/bacterium interface within a sort of bio-doping mechanism. Interestingly, this triggers a blue-shift in the photonic response. This work demonstrates that our hybrid plasmonic/photonic device can be a low-cost and portable platform for the detection of common contaminants in food and water

Light manipulation in multilayered photonic structures

L'abstract è presente nell'allegato / the abstract is in the attachmen

Photoswitchable Plasmon-Exciton Coupling in Photochromic Systems

The interaction between light and matter is ubiquitous and the phenomenon has been studied by scientists for so long that one could think that science would have all the answers to relevant questions already. Yet how light and matter interact still holds unexplored and interesting territory for science. Of interest to researchers in recent years has been the interaction of light and matter that leads to a coupling of the two in the so-called strong coupling regime. In this dissertation, strong coupling between light and matter will be investigated and made switchable in two different experimental setups. In general, strong coupling between photons and molecular excitons leads to the creation of hybrid modes, different from the original and uncoupled modes, visible as the upper and lower polariton branches of an avoided crossing in the dispersion relation, all measured here with the optical measuring technique of spectroscopic ellipsometry. Results are in very good agreement with electrodynamic modeling. Even in situ measurements of switchable coupling are recorded. The role of the photonic coupling partner will be taken by plasmonic modes, either surface plasmon polaritons excited through the use of a prism in a Kretschmann configuration, or Tamm plasmons, a somewhat newer plasmonic coupling partner gathering interest in research lately and here explored for the first time in the scientific literature with regard to strong coupling with molecular excitons and with regard to being made photoswitchable. The switching is achieved through the excitonic partner, a photochromic molecule that can change conformation, and thus the availability of the excitonic mode, by exposure to UV light. In this way, the light-matter coupling in the sample setups can be switched off and on.Die Wechselwirkung zwischen Licht und Materie ist allgegenwärtig und das Phänomen wurde von Wissenschaftlern so lange untersucht, dass man glauben könnte, die Wissenschaft habe bereits alle Antworten auf relevante Fragen. Doch wie Licht und Materie interagieren, ist für die Wissenschaft noch unerforschtes und interessantes Gebiet. Für Forscher war in den letzten Jahren die Wechselwirkung von Licht und Materie von Interesse, die zu einer Kopplung der beiden im sogenannten starken Kopplungsregime führt. In dieser Dissertation wird die starke Kopplung zwischen Licht und Materie untersucht und in zwei verschiedenen Versuchsaufbauten optisch schaltbar gemacht. Im Allgemeinen führt eine starke Kopplung zwischen Photonen und molekularen Exzitonen zur Erzeugung von Hybridmoden, die sich von den ursprünglichen und ungekoppelten Moden unterscheiden und als obere und untere Polaritonenäste einer vermiedenen Kreuzung in der Dispersionsrelation zu sehen sind. Diese werden in dieser Thesis mittels der optischen Messtechnik der spektroskopischen Ellipsometrie vermessen und charakterisiert. Die Ergebnisse stimmen sehr gut mit der elektrodynamischen Modellierung überein. Auch in-situ-Messungen der schaltbaren Kopplung werden aufgezeichnet. Die Rolle des photonischen Kopplungspartners wird von plasmonischen Moden übernommen, entweder von Oberflächenplasmonpolaritonen, die durch die Verwendung eines Prismas in einer Kretschmann-Konfiguration angeregt werden, oder von Tamm-Plasmonen, einem etwas neueren plasmonischen Kopplungspartner, der in letzter Zeit Forschungsinteresse geweckt hat. Hier wird erstmals das Verhalten solcher Plasmonen hinsichtlich starker Kopplung mittels photoschaltbarer molekularer Exzitonen untersucht. Das Umschalten erfolgt durch den exzitonischen Partner, ein photochromes Molekül, das durch Belichtung mit UV-Licht die Konformation und damit die Verfügbarkeit des exzitonischen Modus ändern kann. So kann die Licht-Materie-Kopplung in den Probenaufbauten ein- und ausgeschaltet werden

Recent Progress on Exciton Polaritons in Layered Transition‐Metal Dichalcogenides

Exciton polaritons (EPs) are half‐light, half‐matter quasiparticles formed due to the coupling between photons and excitons in semiconductors. Their uniqueness lies at the strong light–matter interactions and long‐distance transport, thus promising for many novel applications in photonics, information, and quantum technologies. Recently, EPs in group‐VI transition‐metal dichalcogenides (TMDs) have attracted a lot of research interest due to their room‐temperature stability, long‐distance propagation, and controllability through electric gating, valley‐selective optical pumping, and precise thickness control. In this progress report, recent studies of EPs in TMDs are reviewed, highlighting their key properties and functionalities, and then discussing the potential directions for future research

Hyperbolic Resonances of Metasurface Cavities

We propose a new class of optical resonator structures featuring one or two metasurface reflectors or metacavities and predict that such resonators support novel hyperbolic resonances. As an example of such resonances we introduce hyperbolic Tamm plasmons (HTPs) and hyperbolic Fabry-Perot resonances (HFPs). The hyperbolic optical modes feature low-loss incident power re-distribution over TM and TE polarization output channels, clover-leaf anisotropic dispersion, and other unique properties which are tunable and are useful for multiple applications.Comment: 20 pages, 10 figure