Chip-integrated whispering-gallery resonators enable compact and wavelength-agile nonlinear optical frequency synthesizers. So far, the most flexible phase-matching technique, i.e. quasi phase matching, has not been applied in this configuration. The reason is the lack of suitable thin films with alternating crystal structure on a low-refractive-index substrate. Here, we demonstrate an innovative method of realizing thin film substrates suitable for quasi phase matching by field-assisted domain engineering of lithium niobate, and subsequent direct bonding and polishing. We are able to fabricate high-Q on-chip WGRs with these substrates by using standard semiconductor manufacturing techniques. The Q-factors of the resonators are up to one million, which allows us to demonstrate quasi-phase-matched second-harmonic generation in on-chip WGRs for the first time. The normalized conversion efficiency is 9 × 10 −4 mW −1 . This method can also be transferred to other material systems. * These authors contributed equally to this work.

Polymer‐based synthetic mimics of antimicrobial peptides (SMAMPs) show promising antimicrobial activity in solution and as surface‐attached networks. In this paper, their potential as active ingredients in layer‐by‐layer (LbL) assemblies is evaluated. These consist of the weak, anionic polyelectrolyte poly(acrylic acid), and either the hydrophobic butyl SMAMP or the hydrophilic diamine SMAMP (both of which are cationic, weak polyelectrolytes). In situ surface plasmon resonance spectroscopy is used to optimize the LbL assembly conditions. An “overshooting” is observed when depositing the SMAMP layer. Zeta potential measurements show that the layer charge inversion is reduced at each build‐up step due to layer interpenetration. Thus, the positive charge of LbL assemblies with SMAMPs as the top layer is low; a significant part is consumed to maintain layer stability. This leads to reduced antimicrobial activity. Fine‐tuning of the assembly and post‐treatment conditions leads to SMAMP‐PAA LbL systems with optimized antimicrobial activity and stability.

This work presents the influence of dopants on viscosity in an uncured liquid state as well as on refractive index, Abbe number, optical loss, and glass transition temperature of different polymer compositions. The base material consists of Genomer 2263, a bisphenol, an epoxy diacrylate as matrix polymer, and benzyl methacrylate as comonomer. As dopants, the soluble aromatic guest‐molecules 9‐bromophenantrene and 9‐vinylcarbazole are investigated. The viscosity can be adjusted by different mixtures of the matrix polymer and comonomer from 3000 down to 4 mPa sec. Depending on the type and content of the dopants, the refractive index, Abbe number, and the glass transition temperature can be adjusted. The refractive indices increase linear at 589 nm and 20°C from 1.572 to 1.638 by doping, with Abbe numbers between 20 and 30. At this wavelength, the optical losses were determined to be around 2 dB · cm−1. The glass transition temperature can be tailored between 50 and 98°C. A way to use high amounts of optical dopants is presented, which opens up the way for different shaping technologies like inkjet printing of optical components. Copyright © 2016 John Wiley & Sons, Ltd.

The article from this special issue was previously published in Polymers for Advanced Technologies, Volume 28, Issue 4, 2017. For completeness we are including the title page of the article below. The full text of the article can be read in Issue 28:4 on Wiley Online Library: http://onlinelibrary.wiley.com/doi/10.1002/pat.3920/full

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