Optimization of Low-Loss AL2O3AL_{2}O_{3} Waveguide Fabrication for Application in Active Integrated Optical Devices

In this paper we will present the fabrication and properties of reactively co-sputtered $AL_{2}O_{3}$ layers, being a very promising host material for active integrated optics applications such as rare-earth ion doped laser devices. The process optimization towards a reactive co-sputtering process, which resulted in stable, target condition-independent deposition of $AL_{2}O_{3}$ with high optical quality will be discussed in detail. The loss value of as-deposited optical waveguides sputtered by the optimized process has been measured. The loss in the near infrared wavelength range was 0.3 dB/cm. Furthermore $AL_{2}O_{3}$ material hosts fabricated by sputtering techniques are compatible with Si-based integrated optical technology and allow for uniform deposition over a large substrate area

Focused Ion Beam Nano-structuring for Applications in Photonics

To date, nano- and micro-structuring has commonly been implemented by a combination of specifically optimized processes of electron-beam lithography and reactive ion etching, thus limiting the range of materials that can be structured to only a few. In this talk we will introduce focused ion beam (FIB) milling as an emerging technology that enables fast, reliable and well-controlled nanometer-size feature definition. Since the method involves physical removal of material by a beam of ions, the technique can be adapted and optimized almost for any material system. We will introduce the technique and discuss the basic application areas. In particular, we have investigated the impact of parameters such as ion beam current, dwell time, scanning strategy, and dielectric charging. We will discuss strategies to optimize the nano-structuring processes that are strongly dependent on the geometry of the desired structure. Finally, we will report our recent results on utilization and optimization of the focused ion beam technique for fabrication of nano-structures in integrated photonic devices on several material platforms such as Si, Al2O3, Y2O3, Sc2O3, and KY(WO4)2

Congruent families and invariant tensors

Classical results of Chentsov and Campbell state that -- up to constant multiples -- the only $2$-tensor field of a statistical model which is invariant under congruent Markov morphisms is the Fisher metric and the only invariant $3$-tensor field is the Amari-Chentsov tensor. We generalize this result for arbitrary degree $n$, showing that any family of $n$-tensors which is invariant under congruent Markov morphisms is algebraically generated by the canonical tensor fields defined in an earlier paper

Focused-ion-beam processing for photonics

Although focused ion beam (FIB) processing is a well-developed technology for many applications in electronics and physics, it has found limited application to photonics. Due to its very high spatial resolution in the order of 10 nm, and its ability to mill almost any material, it seems to have a good potential for fabricating or modifying nanophotonic structures such as photonic crystals. The two main issues are FIB-induced optical loss, e.g., due to implantation of gallium ions, and the definition of vertical sidewalls, which is affected by redeposition effects. The severity of the loss problem was found to depend on the base material, silicon being rather sensitive to this effect. The optical loss can be significantly reduced by annealing the processed samples. Changing the scanning strategy for the ion beam can both reduce the impact of gallium implantation and the redeposition effect

Focused ion beam milling strategy for sub-micrometre holes in silicon

Focused ion beam (FIB) milling can be used as a tool to fabricate structures with sub-micrometer details. The slab material can be silicon, for example, which can then be used as a mould for nano-imprint lithography, or in silicon on insulator (SOI) layer configuration suitable for photonic applications. In the latter, additional effort has to be taken to prevent high FIB induced losses, due to ion implantation and material crystal damage. Perfectly vertical sidewalls are, in principle, required for photonic crystal applications to guarantee low-loss propagation; sidewall angles of 5 degrees can already induce a 8 dB/mm propagation loss. We report on optimization of the sidewall angle (FIB) fabricated submicron diameter holes. Our best case results show that sidewall angles as small as 1.5 degree are possible in Si membranes and 5 degree for (bulk) Si and SOI by applying larger doses and using a spiral scan method

Testing Creditor Moral Hazard in Sovereign Bond Markets: A Unified Theoretical Approach and Empirical Evidence

This paper critically evaluates the existing empirical literature on creditor moral hazard in sovereign bond markets, proposes a unified theoretical approach to test for IMF-induced creditor moral hazard, and provides empirical evidence, using daily sovereign bond market spreads of Indonesia and Korea. The results suggest that IMF-related news regarding program negotiations and approval may be associated with creditor moral hazard, but their impact on spreads is short-lived, indicating that creditor moral hazard could be best described as a short-run phenomenon.Creditor moral hazard, financial markets, the IMF, and news