News

Paper Published in Applied Optics

On the 6th, Applied Optics published our manuscript entitled, Optimized single-shot laser ablation of concave mirror templates on optical fibers. The manuscript describes a process for realizing mirror templates on the tips of optical fibers by single-shot CO₂ laser ablation. It also presents a systematic study of the influence of the pulse power, pulse duration, and laser spot size on their geometry. The investigation provides new insights into CO₂ laser ablation of optical fibers and should help improve current models. Notably, the study finds that the radius of curvature, depth, and diameter of the templates exhibit extrema as a function of the power and duration of the ablation pulse, and shows that compound convex–concave shapes can be obtained. In the paper, we also identify regimes of ablation parameters that lead to mirror templates with favorable geometries for use in cavity quantum electrodynamics and optomechanics.

Ph.D. student Thibaud Ruelle was the driving force behind this work, carrying out the experiments and modelling the results. Dr. Floris Braakman led and supervised the work as part of his 2015 Ambizione grant from the Swiss National Science Foundation.

Basel-Zürich 3-1

On the 25th, post-doc Dr. Marcus Wyss and Ph.D. student Giulio Romagnoli traveled to the Letzigrund stadium to represent the group in support of the local football club at the semi-final of the 2019 Swiss Cup. They enjoyed watching FC Basel thrash a team from a neighboring city in a 3-1 victory worth a spot in the Swiss Cup final. A good time was had both at the match and on the ride to and from the game on a ‘special’ train for FC Basel fans.

Zurich Instruments User Meeting

On the 25th and 26th, Ph.D students Thibaud Ruelle, Hinrich Mattiat, Simon Philipp, and Nicola Rossi; post-doc Dr. Boris Groß; and Prof. Poggio attended the 3rd Zurich Instruments User Meeting on SPM & Magnetism held at ETH Zürich. The meeting was hosted by Prof. Christian Degen and included talks, practical tutorials, and tours of labs and of Zurich Instruments headquarters. Prof. Poggio gave a talk on the morning of the 25th entitled, “New scanning probes for nanomagnetic imaging”.

Review on Nanowire Force Sensing Published

On the 16th, Nanotechnology published a topical review written by Dr. Floris Braakman and Prof. Poggio entitled, Force sensing with nanowire cantilevers. The paper discusses the motivation behind using nanowires as force transducers, explain the methods of force sensing with nanowire cantilevers, and gives an overview of the experimental progress so far and future prospects of the field.

Prof. Poggio at DPG Spring Meeting

On the 2nd, Prof. Poggio gave an invited talk at the annual Spring Meeting of the Deutsche Physikalische Gessellschaft (DPG) in Regensburg, Germany. On the invitation of session organizer, Dr. Denys Makarov, Prof. Poggio gave a talk entitled, “Magnetization configurations and reversal of individual ferromagnetic nanotubes“. This talk was part of a special symposium on “Geometry, Topology, and Condensed Matter“.

Seminar at Walter Schottky Institute

On the 1st, Prof. Poggio visited Prof. Gregor Kolbmueller and Prof. Jonathan Finley at the Walter Schottky Institute (WSI) of the Technical Univeristy of Munich (TUM). He discussed an ongoing collaboration and visited research groups at TUM. In the afternoon, he gave a ‘Schottky Seminar’ entitled, “New scanning probes for nanomagnetic imaging“.

Group at APS March Meeting

From the 4th to the 8th, members of the group attended the annual APS March Meeting, which was held in Boston this year. Ph.D. students Hinrich Mattiat, Nicola Rossi, and Lorenzo Ceccarelli; post-docs Dr. Floris Braakman and Dr. Marcus Wyss; and Prof. Poggio made the trip to attend the 11,000-person conference. Hinrich gave a talk entitled, “FEBID-grown iron and cobalt nanowires as magnetic force sensors“; Nicola a talk entitled, “Magnetic force sensing using a self-assembled GaAs nanowire with a MnAs tip“; Lorenzo a talk entitled, “Imaging individual superconducting vortices in amorphous Mo_0.8Si_0.2 by scanning SQUID-on-tip“; Marcus a talk entitled, “Imaging the stray field of chiral artificial spin ice with scanning nanoSQUID-on-tip“; and Floris a talk and a poster entitled, “Optimized single-shot laser ablation of concave mirror templates on optical fibers” and “Hole spins in Ge/Si nanowires“, respectively.

Physics II for Physicists Starts

On Thursday the 21st, the lecture “Introduction to Physics II for Physicists: Electrodynamics and Optics” began and will run until Friday, May 24th. The exam is scheduled for June 20st, 2019, 10:00 – 13:00. The lecture covers the basics of electrostatics, magnetostatics, electrodynamics, and optics. Prof. Philipp Treutlein and Prof. Poggio are sharing lecturing responsibilities.

Group Members at Arosa Meeting or Lorenzo Speaks and Thibaud Knows He’s #1

From the 4^th to the 8^th, members of the group attended the 8^th NCCR Winter School and 9^th NCCR QSIT General Meeting in Arosa, Switzerland. Ph.D. student Hinrich Mattiat attended both the school and the meeting, while Ph.D. students Lorenzo Ceccarelli, Giulio Romagnoli, Thibaud Ruelle, post-doc Boris Groß, and Prof. Poggio attended the meeting. Hinrich and Thibaud presented posters on their work and Lorenzo gave a talk on the 8^th entitled, “Imaging individual superconducting vortices in amorphous Mo Si by scanning SQUID-on-tip”. On the afternoon of the 7^th, Thibaud — after predicting victory — crushed the competition and won the annual QSIT ski race, becoming the first group member to do so. Congratulations! Also, a special thanks to Ilona Blatter for her long and crucial service to QSIT and to Klara Berg for organizing and excellent meeting.

Floris at Nano in the Snow

From the 23rd to the 25th, post-doc Dr. Floris Braakman attended the annual “Nanoscience in the Snow” Workshop organized by the Swiss Nanoscience Institute and held this year at the Hotel Crystal Braunwald. Floris gave a talk in the morning of Thursday the 24th.

Nanowire MFM Paper Published

On the 2nd, our manuscript entitled, Magnetic force sensing using a self-assembled nanowire, was published by Nano Letters. In the study, we present a scanning magnetic force sensor based on an individual magnet-tipped GaAs nanowire (NW) grown by molecular beam epitaxy. Its magnetic tip consists of a final segment of single-crystal MnAs formed by sequential crystallization of the liquid Ga catalyst droplet. We characterize the mechanical and magnetic properties of such NWs by measuring their flexural mechanical response in an applied magnetic field. Comparison with numerical simulations allows the identification of their equilibrium magnetization configurations, which in some cases include magnetic vortices. To determine a NW’s performance as a magnetic scanning probe, we measure its response to the field profile of a lithographically patterned current-carrying wire. The NWs’ tiny tips and their high force sensitivity make them promising for imaging weak magnetic field patterns on the nanometer-scale, as required for mapping mesoscopic transport and spin textures or in nanometer-scale magnetic resonance.

Ph.D. student Nicola Rossi led the research and carried out the experiments. Dr. Boris Groß developed and ran the micromagnetic simulations. Ph.D. student Florian Dirnberger and Prof. Dominique Bougeard from the Universität Regensburg grew the magnet-tipped NWs used in the experiments.