Metal–Dielectric Hybrid Dimer Nanoantenna: Coupling between Surface Plasmons and Dielectric Resonances for Fluorescence Enhancement

Dimers made of noble metal particles possess extraordinary field enhancements but suffer from large dissipation, whereas low-loss dielectric dimers are limited by relatively weak optical confinement. Hybrid systems could take advantages from both worlds. In this contribution, we study the mode coupling in a hybrid dimer with rigorous dipole–dipole interaction theory and explore its potential in fluorescence enhancement. We first discovered that the direct coupling between metal surface–plasmon resonance and dielectric electric–dipole mode creates a hybridized mode due to the strong electric–electric dipole–dipole interaction between the constituent nanoparticles, whereas the dielectric magnetic–dipole mode can only indirectly couple to the plasmons on the basis of the induced electric–magnetic dipole–dipole interaction. When an electric/magnetic quantum emitter couples to the hybrid dimer, the emitter selectively excites the electric/magnetic (magnetic/electric) resonant modes of the dimer for emitter orientation parallel (perpendicular) to the dimer axis. Our study shows that the hybrid dimer simultaneously possesses high field enhancement and low-loss features, which demonstrates a fluorescence excitation rate 40% higher than that of the pure dielectric dimer and an average quantum yield 30% higher than that of the pure metallic dimer. On top of that, the unique asymmetrical structure of the hybrid dimer directs 20% more radiation toward the dielectric side, hence improving the directivity of the dimer as an antenna

Hybrid Mushroom Nanoantenna for Fluorescence Enhancement by Matching the Stokes Shift of the Emitter

Nanoantenna-enhanced fluorescence is a promising method in many emergent applications, such as single molecule detection. The excitation and emission wavelengths of emitters can be well separated depending on the corresponding Stokes shifts, preventing optimal fluorescence enhancement by a rudimentary nanoantenna. We illustrate a hybrid mushroom nanoantenna that can achieve overall enhancements (e.g., excitation rate, quantum yield, fluorescence enhancement) in fluorescence emission. The nanoantenna is made of a plasmonic metal stipe and a dielectric cap, and the resonances can be flexibly and independently controlled to match the Stokes shift of the emitter. By fully leveraging the advantages of the large field enhancement from the metal and the low loss feature from the dielectric, a fluorescence enhancement factor (far field intensity) twice (20 times) as high as that from a pure metallic antenna can be attained, accompanied by improved directivity. Approximately 70% of the overall radiation was directed toward the mushroom cap via coupling to the dielectric resonance, which could benefit the collection efficiency. This hybrid concept introduces a way to build high-performance nanoantennas for fluorescence enhancement applications

Who will follow the leader? Managers' perceptions of management development activities: an international comparison: SKOPE Research Paper No. 51, Autumn 2004

This article contributes to the on-going debate surrounding management education and development through an examination of the development experiences of managers studying for an MBA by distance learning at Warwick Business School. It analyses the extent to which management development opportunities, both formal and informal, are seen to support managers in their day-to-day roles and deliver those skills necessary for the future. The research also provides the opportunity to compare responses from UK managers with those from managers in other countries. The survey evidence shows that in some respects the experience of UK and Overseas respondents are quite similar; they both receive large amounts of training and development from their employers and show a preference for more ‘non-formal’ routes of learning. In other ways their experiences are quite different: UK managers take up their first full-time job and their first managerial appointment earlier than the overseas respondents and overseas respondents placed much more emphasis on networking and learning from outside their own organisations than did UK managers. The research also suggests that integrating management development activities with other human resource policies and practices, such as performance evaluation and reward remains problematic and that there is a strong perception amongst managers both in the UK and overseas that their organisations do not view management development in a strategic way. When looking at future development needs respondents from both the UK and overseas highlighted the need for leadership skills as a priority for themselves but focused on more general management and operational skills as the main priority for their colleagues. One possible explanation for this is that the respondents were only to well aware of the fact that that leaders need followers. This is, however, a view at which is at odds with current policy arguments in the UK where leadership skills are seen to be necessary for all managers