Strong light-matter coupling in organic microcavities : investigating the fundamental principles of strong coupling in strongly disordered materials experimentally

Strong light–matter coupling gives rise to intriguing possibilities like Bose-Einstein condensation at room temperature. In this context, organic semiconductors are particularly attractive because they combine large oscillator strengths with high exciton binding energies and thus readily enable large light–matter coupling strengths up to room temperature. Yet, in these commonly strongly disordered materials, the applicability of fundamental predictions developed for systems of high order needs to be verified. Hence, the validity of the theoretically predicted form of the coupling strength and of the coupled oscillator model is tested for strongly coupled organic microcavities in this thesis. Experimental investigations of metal-clad microcavities confirm the coupling strength to be proportional to the electric field with which the excitons interact and to the square root both of the oscillator strength of the material and of the number of chromophores inside the microcavity. Systematically varying these parameters demonstrates a non-zero threshold for the onset of the strong coupling regime for the first time, which confirms the applicability of the coupled oscillator model also for strongly disordered systems. Moreover, the effect of the coupling strength on the photoluminescence from organic microcavities is investigated. For metal-clad cavities, but not for microcavities with dielectric mirrors, an increase of the luminescence intensity with increasing coupling strength was found. For the latter system, a systematic study aimed to determine the properties of the cavity and of the organic material which are crucial for polariton lasing. However, experiments did not yield polariton lasing, for which two potential reasons are identified: (1) the vanishing of modes close to resonance and (2) pronounced bimolecular quenching in the studied material. Since organic microcavities are complex, systematic studies as presented in this thesis are an important step towards a more profound understanding of organic polaritons."This work was supported by the Engineering and Physical Sciences Research Council [grant number EP/L015110/1]" -- Acknowledgement

Exploration Blueprint: Data Book

The material contained in this report was compiled to capture the work performed by the National Aeronautics and Space Administration's (NASA's) Exploration study team in the late 2002 timeframe. The "Exploration Blueprint Data Book" documents the analyses and findings of the 90-day Agency-wide study conducted from September - November 2002. During the summer of 2002, the NASA Deputy Administrator requested that a study be performed with the following objectives: (1) Develop the rationale for exploration beyond low-Earth orbit (2) Develop roadmaps for how to accomplish the first steps through humans to Mars (3) Develop design reference missions as a basis for the roadmaps 4) Make recommendations on what can be done now to effect this future This planning team, termed the Exploration Blueprint, performed architecture analyses to develop roadmaps for how to accomplish the first steps beyond LEO through the human exploration of Mars. The previous NASA Exploration Team activities laid the foundation and framework for development of NASA's Integrated Space Plan. The reference missions resulting from the analysis performed by the Exploration Blueprint team formed the basis for requirement definition, systems development, technology roadmapping, and risk assessments for future human exploration beyond low-Earth orbit. Emphasis was placed on developing recommendations on what could be done now to effect future exploration activities. The Exploration Blueprint team embraced the "Stepping Stone" approach to exploration where human and robotic activities are conducted through progressive expansion outward beyond low-Earth orbit. Results from this study produced a long-term strategy for exploration with near-term implementation plans, program recommendations, and technology investments. Specific results included the development of a common exploration crew vehicle concept, a unified space nuclear strategy, focused bioastronautics research objectives, and an integrated human and robotic exploration strategy. Recommendations from the Exploration Blueprint included the endorsement of the Nuclear Systems Initiative, augmentation of the bioastronautics research, a focused space transportation program including heavy-lift launch and a common exploration vehicle design for ISS and exploration missions, as well as an integrated human and robotic exploration strategy for Mars