Optical nano-imaging of gate-tunable graphene plasmons

The ability to manipulate optical fields and the energy flow of light is central to modern information and communication technologies, as well as quantum information processing schemes. However, because photons do not possess charge, a way of controlling them efficiently by electrical means has so far proved elusive. A promising way to achieve electric control of light could be through plasmon polaritons—coupled excitations of photons and charge carriers—in graphene. In this two-dimensional sheet of carbon atoms, it is expected that plasmon polaritons and their associated optical fields can readily be tuned electrically by varying the graphene carrier density. Although evidence of optical graphene plasmon resonances has recently been obtained spectroscopically, no experiments so far have directly resolved propagating plasmons in real space. Here we launch and detect propagating optical plasmons in tapered graphene nanostructures using near-field scattering microscopy with infrared excitation light. We provide real-space images of plasmon fields, and find that the extracted plasmon wavelength is very short—more than 40 times smaller than the wavelength of illumination. We exploit this strong optical field confinement to turn a graphene nanostructure into a tunable resonant plasmonic cavity with extremely small mode volume. The cavity resonance is controlled in situ by gating the graphene, and in particular, complete switching on and off of the plasmon modes is demonstrated, thus paving the way towards graphene-based optical transistors. This successful alliance between nanoelectronics and nano-optics enables the development of active subwavelength-scale optics and a plethora of nano-optoelectronic devices and functionalities, such as tunable metamaterials, nanoscale optical processing, and strongly enhanced light–matter interactions for quantum devices and biosensing applications.     

Towards a Dynamic Model of Organisational Flexibility

Organisational flexibility, as the ability to adapt quickly to new or changing environments, has received growing attention from both researchers and managers as a key driver for companies to survive and prosper in turbulent and unpredictable environments. Although many scholars have studied the complex nature and multidimensional structure of this construct, research on a comprehensive model, which explains the relationships between its key variables and consequent side effects of such iterations, remains a challenge. We explore these interactions and the dynamic adaptation processes applying system dynamics modelling to develop a more robust organisational flexibility theory. The objective of this paper is twofold, to provide dynamic propositions related to several strategies along different enterprise lifecycle stages and to complement the transition guidelines proposed by the organizational flexibility framework. The results suggest that decision concerning flexible capabilities management and organizational responsiveness can be improved if organizational flexibility is analysed and evaluated incorporating the time-varying dimension. The analysis help to test and expand current theory, envisage new theoretical propositions and provide new alternatives for empirical results about the complex construct of organizational flexibility.     

The microcosmos of cancer

The discovery of microRNAs (miRNAs) almost two decades ago established a new paradigm of gene regulation. During the past ten years these tiny non-coding RNAs have been linked to virtually all known physiological and pathological processes, including cancer. In the same way as certain key protein-coding genes, miRNAs can be deregulated in cancer, in which they can function as a group to mark differentiation states or individually as bona fide oncogenes or tumour suppressors. Importantly, miRNA biology can be harnessed experimentally to investigate cancer phenotypes or used therapeutically as a target for drugs or as the drug itself.