Diffractive effects in singly-resonant continuous-wave parametric oscillators

This paper presents a detailed numerical study of the effect of focusing on the conversion efficiency of low-loss singly-resonant parametric oscillators with collinear focusing of pump and signal. Results are given for the maximal pump depletion and for pump power levels required for various amounts of depletion, as functions of pump and signal confocal parameters, for kI/kP=0.33 and 0.50. It is found that the ratio of pump depletion to maximal depletion as a function of the ratio of pump power to threshold power agrees with the plane-wave prediction to within 5%, for a wide range of focusing conditions. The observed trends are explained as resulting from intensity and phase dependent mechanisms.Comment: 22 pages, 18 figure

Dispersion-induced generation of higher order transversal modes in singly-resonant optical parametric oscillators

We study the effects of higher order transversal modes in a model of a singly-resonant OPO, using both numerical solutions and mode expansions including up to two radial modes. The numerical and two-mode solutions predict lower threshold and higher conversion than the single-mode solution at negative dispersion. Relative power in the zero order radial mode ranges from about 88% at positive and small negative dispersion to 48% at larger negative dispersion, with most of the higher mode content in the first mode, and less than 2% in higher modes.Comment: 13 pages, 4 figures, PACS Numbers: 42.65.Ky, 42.10.Qj, Key Words: parametric oscillation, phase-matching, diffractio

Political Accountability, Fiscal Conditions, and Local Government Performance – Cross-Sectional Evidence from Indonesia

What makes governments tick? Why are some public institutions more successful than others in managing resources and delivering services? And even more vitally, how can malfunctioning institutions be reformed so that they perform their responsibilities more effectively? This paper contributes to our understanding of theses overarching questions by exploring the interactions between political institutions and public sector performance in the context of decentralization and local governance. It shows -both theoretically and empirically- that performance outcomes are determined by the extent to which people can hold their governments accountable through political institutions. The basic hypothesis underlying this research is that political accountability, either by encouraging sanctions upon non-compliant public agents or simply by reducing the informational gap regarding government activities, will create forceful incentives for elected officials and civil servants to reduce opportunistic behavior and improve performance. Using a cross-sectional regression the hypothesis is empirically tested against evidence from newly empowered local governments in Indonesia. The empirical findings broadly support our hypotheses. Improved public services on the ground, both in terms of quantity and quality, require informed and well functioning decision making processes that allocate resources to priority areas that meet the demand of the broader community.governance, public services, fiscal decentralization

Charge excitation dynamics in bosonic fractional Chern insulators

The experimental realization of the Harper-Hofstadter model in ultra-cold atomic gases has placed fractional states of matter in these systems within reach---a fractional Chern insulator state (FCI) is expected to emerge for sufficiently strong interactions when half-filling the lowest band. The experimental setups naturally allow to probe the dynamics of this topological state, yet little is known about its out-of-equilibrium properties. We explore, using density matrix renormalization group (DMRG) simulations, the response of the FCI state to spatially localized perturbations. After confirming the static properties of the phase we show that the characteristic, gapless features are clearly visible in the edge dynamics. We find that a local edge perturbation in this model propagates chirally independent of the perturbation strength. This contrasts the behavior of single particle models with counter-propagating edge states, such as the non-interacting Harper-Hofstadter model, where the chirality is manifest only for weak perturbations. Additionally, our simulations show that there is inevitable density leakage from the first row of sites into the bulk, preventing a naive chiral Luttinger theory interpretation of the dynamics.Comment: 4+epsilon pages, 4 pages of supplementary material and a total of 8 figures. Published version with updated title, discussion, references, and supplementary informatio

The Quality of Insurance Intermediary Services – Empirical Evidence for Germany

Insurance intermediaries help consumers to economize on information and transaction costs in insurance markets. However, competing insurance intermediaries provide heterogeneous services, which are difficult to assess by incompletely informed consumers. Transaction costs economics, search theory and principal agent theory provide arguments on product quality differences between the two main distribution channels in insurance markets (exclusive agents vs. independent intermediaries). The present paper uses a sample of 927 insurance intermediaries in Germany. By performing OLS estimations we test the impact of the different distribution channels, but also of other factors relating to the information processing activities on intermediaries’ service quality. Depending on the proxies used for service quality, we find mixed evidence for the “product quality” hypothesis according to which independent intermediaries provide better service quality than exclusive agents. We find that service quality depends also to a large extent on the information gathering and processing activities of the individual intermediaries.Insurance Distribution Channels, Service Quality