Strong coupling of ionising transitions

We demonstrate that a ionising transition can be strongly coupled to a photonic resonance. The strong coupling manifests itself with the appearance of a narrow optically active resonance below the ionisation threshold. Such a resonance is due to electrons transitioning into a novel bound state created by the collective coupling of the electron gas with the vacuum field of the photonic resonator. Applying our theory to the case of bound-to-continuum transitions in microcavity-embedded doped quantum wells, we show how those strong-coupling features can be exploited as a novel knob to tune both optical and electronic properties of semiconductor heterostructures.Comment: 10 pages, 7 figure

Design of mid-IR and THz quantum cascade laser cavities with complete TM photonic bandgap

We present the design of mid-infrared and THz quantum cascade laser cavities formed from planar photonic crystals with a complete in-plane photonic bandgap. The design is based on a honeycomb lattice, and achieves a full in-plane photonic gap for transverse-magnetic polarized light while preserving a connected pattern for efficient electrical injection. Candidate defects modes for lasing are identified. This lattice is then used as a model system to demonstrate a novel effect: under certain conditions - that are typically satisfied in the THz range - a complete photonic gap can be obtained by the sole patterning of the top metal contact. This possibility greatly reduces the required fabrication complexity and avoids potential damage of the semiconductor active region.Comment: 14 pages, 14 figure

Entrepreneurship As Regional Development Catalyst

Entrepreneurship is more and more considered a key driver of economic performance. Recent works in the literature on this research area (see Saxenian, 1994; Audretsch and Keilbach, 2004; Cooke, 2004; Cassia, Fattore and Paleari, 2006) suggest that there is a positive link between entrepreneurship capital, regional economic performance and the creation of new firms and businesses. This kind of intangible assets promotes the spillover of knowledge, becoming crucial in building firms and regional innovation capability and strengthening learning capacities. Entrepreneurship is, thus, about change and innovation. In relation to these concepts, the aim of the paper is to highlight the entrepreneurial dimension behind the creation of firms formed around new business ideas in a knowledge-based economy, where value-relevant assets are expected to consist predominately of intangible and non-marketable assets. To this purpose, we focus on companies going public on the Alternative Investment Market (AIM), a market dedicated to young and growing companies in both science and non-science based industries. The AIM was launched in 1995, allowing to a large number of SME to go public in the UK, and, today, is recognized as the most successful secondary market in Europe, brought forward as an example by other stock exchanges in mainland Europe. In the paper we investigate the post-IPO performance of listed firms, during the period going from 1995 to 2002, with the aim, first, to highlight the determinants shaping that performance and influencing the local milieu and, secondly, to underline the role of entrepreneurship. The results of this work have some policy implications both at national and regional level. At the national level, policy makers should take into account the relevance of an efficient financial system, in particular the emerging role of secondary markets, and try to remove financial constraints that hamper the the prospect of new businesses. At the regional level, political intervention should aim to promote entrepreneurial activities, which ease the regional process of change, for example, by encouraging the propensity to risk and facilitating the access to external capital

The knowledge regions in the enlarged Europe

Since the Lisbon agenda in 2000, Europe stated the goal to become the most advanced knowledge economy in the world relying specifically on the increase and strengthen of its human capital and technological endowments. However, given the presence of localized externalities in the knowledge accumulation process, this policy may produce distortive and unwanted consequences at the territorial level reinforcing the existing high inequalities among regions. Another crucial feature to be considered is the recent enlargement process of the European Union which has brought on stage new players characterized by a low average level of knowledge activity accompanied by a huge degree of internal territorial disparity. The aim of this paper is to identify the “knowledge regions†in Europe and to examine their main territorial features. To this aim we first build, for 287 regions belonging to 31 European countries, a comprehensive picture of the two variables - human capital and technological activity - which constitute the main pillars of the knowledge economy. For each of these two variables we construct several indicators examining their spatial distribution across the European regions. Further, we compute two synthetic indicators for human capital and technology and, on the basis of these two dimensions, we finally identify the knowledge regions.

Photovoltaic Probe of Cavity Polaritons in a Quantum Cascade Structure

The strong coupling between an intersubband excitation in a quantum cascade structure and a photonic mode of a planar microcavity has been detected by angle-resolved photovoltaic measurements. A typical anticrossing behavior, with a vacuum-field Rabi splitting of 16 meV at 78K, has been measured, for an intersubband transition at 163 meV. These results show that the strong coupling regime between photons and intersubband excitations can be engineered in a quantum cascade opto-electronic device. They also demonstrate the possibility to perform angle-resolved mid-infrared photodetection and to develop active devices based on intersubband cavity polaritons.Comment: submitted to Applied Physics Letter

Proof-of-principle of surface detection with air-guided quantum cascade lasers

We report a proof-of-principle of surface detection with air-guided quantum cascade lasers. Laser ridges were designed to exhibit an evanescent electromagnetic field on their top surface that can interact with material or liquids deposited on the device. We employ photoresist and common solvents to provide a demonstration of the sensor setup. We observed spectral as well as threshold currents changes as a function of the deposited material absorption curve. A simple model, supplemented by 2D numerical finite element method simulations, allows one to explain and correctly predict the experimental results

On Firm Growth and Innovation. Some new empirical perspectives using French CIS (1992-2004)

In the paper we wish to examine if the firms that innovate know a higher growth than the firm that do not. We use diverse waves of CIS for the French industries over the period 1992- 2004 and carry out different models and new econometric methods (quantile regression). Our main findings are that innovative firms produce more growth than non innovative firms. The estimates show that the results are robust to the different types of models that we have implemented. Process innovators are more productive in terms of growth than product innovators when OLS and Random effects models are used. The reverse is true for Fix effect model and quantile regression. In the three growth equations estimated by GMM the coefficients related to innovation product are always higher. Our study does not give definitive results with respect to the magnitude of the effects of the type of innovation on firm growth.Innovation, process and product, firm growth, CIS

Common Frameworks for Regional Competitiveness - Insights from a Number of Local Knowledge Economies

1. Aims of the paper: in this paper we analysed a number of European regions that in the last ten to fifteen years experienced a process of industrial reconversion moving from traditional sectors-based economies to knowledge economies. With the aim of shaping the transformation paths driving their competitiveness recovery, the analysis was conducted on two levels. First, we tried to identify the most relevant factors of competitiveness behind each region’s renewal process and combined them to shape a number of common trajectories of regional competitiveness. Secondly, we outlined a taxonomy of transformation paths followed by each of the territories under investigation in their development process towards a knowledge economy. Interestingly, all regional ‘success histories’ are strongly dependent on the presence of a tri-polar regional innovation system (RIS) ‘gluing’ firms, institutions and academia. 2. Factors and trajectories of regional competitiveness: Some of the factors of regional competitiveness identified in the analysis (exhaustively listed and described in the full paper) are entrepreneurial motivation, managerial skills, access to private and public financing, the presence of a local technical university. By combining the competitiveness factors specific to each regional ‘success history’, we were able to spot a number of trajectories of regional competitiveness : (i) the Nokia economies trajectory, (ii) the knowledge creation upon invitation trajectory and (iii) the Cambridge way trajectory. The first trajectory includes the Nordic regions of Tampere and Goteborg. The leading factors of development of these regions can be brought back to the successful development strategies of Ericsson and Nokia, in turn based on excellent managerial and organisational skills and a strong international orientation. The second trajectory of regional competitiveness refers to Ireland, Scotland and Wales, characterized by an ‘industrialisation upon invitation’ type of growth based on foreign direct investments. The policy of FDI attraction is largely supported by public incentives and owes its success to the leading role taken up by regional development agencies. The last trajectory of regional competitiveness relates to the high tech cluster of Cambridge (UK), emerged and developed essentially thanks to the active role of Cambridge University in nurturing the cluster with human capital of excellence and in allowing the faculty members to commercially exploit their skills and technical know how. The most interesting result of this part of the analysis is that the regions under scrutiny owe their virtuous process of competitiveness recovery to three sets of factors, each originating from one of the three territorial actors making up a regional innovation system – firms, institutions, university – so that behind each regional renewal history it is possible to recognize the presence and the ‘functioning’ of a RIS. 3. A taxonomy of regional transformation paths: Next, we classified the development dynamics of the regions investigated above along three paths of economic restructuring. The first path, here defined as the RIS into process, is typical of industrial clusters in engineering-based sectors such as plant engineering, specialised advanced machinery and shipbuilding. Here the relationship with the RIS is developed at a later stage of the cluster life, as the RIS originates in response to the presence of the cluster. This is the case of a number of regions under scrutiny (Baden-Württemberg and Brabant, for instance) where the regional innovation system was specifically designed to support and strengthen local existing industrial specializations. The second regional development path, typical of industrial clustering in science-based sectors such as genetics, IT and biotechnology, follows the opposite ‘direction’. Here the RIS is the main source of the cluster creation and the cluster develops from the regional innovation system by exploiting all the local resources in terms of cooperation and interaction with universities and local institutions. This is the case of regions such as Shannon and Cambridge (UK), which have followed a transformation process here defined as RIS from process, where the pre-existence of the RIS represents a key factor for the organization of a science-based industrial system. The third path may be viewed as the result of a combination between the two different base ‘entities’ described above. In fact, in regions such as Wales, Tampere, Göteborg and North Rhine – Westphalia, science-based clusters have developed from declining engineering-based sectors, passing through the formation of a RIS. In this respect, the transformation process can be defined as RIS through process. In this group of regions, the regional innovation system acted as catalyst for the local system transformation process, driving the regional competitive repositioning through the development of clusters of innovative and high tech firms. In this respect, the process of territorial transformation has taken place thanks to a ‘systemic effort’ and as a result of social interdependencies among territorial actors.