Publications (29)
Low-noise, 2-W average power, 112-fs Kerr-lens mode-locked Ho:CALGO laser at 2.1 um
Weichao Yao, Yicheng Wang, Shahwar Ahmed +4
We report on an in-band pumped soft-aperture Kerr-lens mode-locked Ho:CALGO bulk laser at 2.1 um, generating 2 W of average power with 112 fs pulses at 91-MHz repetition rate. To t…
Variation of magnetic properties of SrFeMoO due to oxygen vacancies
Martin Hoffmann, Victor N. Antonov, Lev V. Bekenov +3
Oxygen vacancies can be of utmost importance for improving or deteriorating physical properties of oxide materials. Here, we studied from first-principles the electronic and magnet…
Olivine-rich exposures at Bellicia and Arruntia craters on (4) Vesta from Dawn FC
Guneshwar Thangjam, Andreas Nathues, Kurt Mengel +9
We present an analysis of the olivine-rich exposures at Bellicia and Arruntia craters using Dawn Framing Camera (FC) color data. Our results confirm the existence of olivine-rich m…
SwarmRob: A Toolkit for Reproducibility and Sharing of Experimental Artifacts in Robotics Research
Aljoscha Pörtner, Martin Hoffmann, Matthias König
Due to the complexity of robotics, the reproducibility of results and experiments is one of the fundamental problems in robotics research. While the problem has been identified by…
Spectral broadening of 2 mJ femtosecond pulses in a compact air-filled convex-concave multi-pass cell
Alan Omar, Tim Vogel, Martin Hoffmann +1
Multi-pass cell (MPC) based temporal pulse compressors have emerged in the last years as a powerful and versatile solution to the intrinsic issue of long pulses from Yb-based high-…
Unique thickness-dependent properties of the van der Waals interlayer antiferromagnet films
Mikhail M. Otrokov, Igor P. Rusinov, MarÃa Blanco-Rey +7
Using density functional theory and Monte Carlo calculations, we study the thickness dependence of the magnetic and electronic properties of a van der Waals interlayer antiferromag…
Prediction and observation of the first antiferromagnetic topological insulator
Mikhail M. Otrokov, Ilya I. Klimovskikh, Hendrik Bentmann +41
Magnetic topological insulators (MTIs) are narrow gap semiconductor materials that combine non-trivial band topology and magnetic order. Unlike their nonmagnetic counterparts, MTIs…
Energy scaling of Kerr-lens modelocked Ho:YAG thin-disk oscillators to the microjoule level
Sergei Tomilov, Mykyta Redkin, Yicheng Wang +3
We demonstrate peak power and pulse energy scaling of Kerr-lens modelocking (KLM) Ho:YAG thin-disk lasers (TDLs) emitting at 2.1-μm wavelength. We compare different laser configur…
50-W average power Ho:YAG SESAM-modelocked thin-disk oscillator at 2.1 um
Sergei Tomilov, Yicheng Wang, Martin Hoffmann +4
Ultrafast laser systems operating with high-average power in the wavelength range from 1.9 um to 3 um are of interest for a wide range of applications for example in spectroscopy,…
Magnetic properties of defect-free and oxygen-deficient cubic SrCoO
Martin Hoffmann, Vladislav S. Borisov, Sergey Ostanin +3
We investigated theoretically electronic and magnetic properties of the perovskite material SrCoO with using a projector-augmented plane-wave method and a Gr…
Surface Albedo and Spectral Variability of Ceres
Jian-Yang Li, Vishnu Reddy, Andreas Nathues +21
Previous observations suggested that Ceres has active but possibly sporadic water outgassing, and possibly varying spectral characteristics in a time scale of months. We used all a…
First-principles investigations of the magnetic phase diagram of GdCaMnO
Hichem Ben Hamed, Martin Hoffmann, Waheed A. Adeagbo +5
We studied for the first time the magnetic phase diagram of the rare-earth manganites series GdCaMnO (GCMO) over the full concentration range based on density f…
Quantitative description of short-range order and its influence on the electronic structure in Ag-Pd alloys
Martin Hoffmann, Alberto Marmodoro, Arthur Ernst +6
We investigate the effect of short-range order (SRO) on the electronic structure in alloys from the theoretical point of view using density of states (DOS) data. In particular, the…
Thermoresponsive Colloidal Molecules
Martin Hoffmann, Miriam Siebenbuerger, Ludger Harnau +6
We fabricated thermoresponsive colloidal molecules of ca. 250 nm size. Electron- and scanning force microscopy reveal the dumbbell-shaped morphology. The temperature dependence of…
GHz repetition rate, sub-100-fs Ho:CALGO laser at 2.1 um with watt-level average power
Weichao Yao, Mohsen Khalili, Yicheng Wang +4
We report on a GHz fundamental repetition rate Kerr-lens mode-locked Ho:CALGO laser emitting at 2.1 um. The laser employs a ring-cavity to increase the fundamental repetition rate…
Laser-driven few-cycle Terahertz sources with high average power
Robin Löscher, Tim Vogel, Samira Mansourzadeh +5
Ultrafast laser-driven terahertz sources are gaining in popularity in an increasingly wide range of scientific and technological applications. However, many fields continue to be s…
Domain wall induced spin-polarized flat bands in antiferromagnetic topological insulators
Evgeniy K. Petrov, Vladimir N. Men'shov, Igor P. Rusinov +6
A flat band in fermionic system is a dispersionless single-particle state with a diverging effective mass and nearly zero group velocity. These flat bands are expected to support e…
Global Photometric Properties of Asteroid (4) Vesta Observed with Dawn Framing Camera
Jian-Yang Li, Lucille Le Corre, Stefan E. Schröder +9
Dawn spacecraft orbited Vesta for more than one year and collected a huge volume of multispectral, high-resolution data in the visible wavelengths with the Framing Camera. We prese…
8.7-W average power, in-band pumped femtosecond Ho:CALGO laser at 2.1 um
Weichao Yao, Yicheng Wang, Sergei Tomilov +7
We report on an in-band pumped SESAM mode-locked Ho:CALGO bulk laser with a record-high average power of 8.7 W and an optical-to-optical efficiency of 38.2% at a central wavelength…
The Power of Color: A Study on the Effective Use of Colored Light in Human-Robot Interaction
Aljoscha Pörtner, Lilian Schröder, Robin Rasch +3
In times of more and more complex interaction techniques, we point out the powerfulness of colored light as a simple and cheap feedback mechanism. Since it is visible over a distan…
Ho3+-doped CALGO crystals for high-power ultrafast 2.1-μm lasers
Anna Suzuki, Pavel Loiko, Weichao Yao +8
Ho3+-doped disordered CaAlGdO4 (CALGO) crystals have recently emerged as a promising gain material platform for next-generation high-power ultrafast 2.1-μm laser systems. This las…
3D Brownian Diffusion of Submicron-Sized Particle Clusters
Martin Hoffmann, Claudia S. Wagner, Ludger Harnau +1
We report on the translation and rotation of particle clusters made through the combination of spherical building blocks. These clusters present ideal model systems to study the mo…
Increased magnetocrystalline anisotropy in epitaxial Fe-Co-C thin films with spontaneous strain
Ludwig Reichel, George Giannopoulos, Sandra Kauffmann-Weiss +8
Rare earth free alloys are in focus of permanent magnet research since the accessibility of the elements needed for nowadays conventional magnets is limited. Tetragonally strained…
High peak-power 2.1-μm femtosecond Holmium amplifier at 100 kHz
Anna Suzuki, Boldizsar Kassai, Yicheng Wang +5
High-power ultrafast laser sources in the short-wave infrared region are of great interest for numerous applications, including secondary sources of radiation and processing of mat…
Tuning the probability of defect formation via substrate strains in SrFeMoO films
Waheed A. Adeagbo, Martin Hoffmann, Arthur Ernst +4
Since oxide materials like SrFeMoO are usually applied as thin films, we studied the effect of biaxial strain, resulting from the substrate, on the electronic and magnetic…
Three-dimensional spectral analysis of compositional heterogeneity at Arruntia crater on (4) Vesta using Dawn FC
Guneshwar Thangjam, Andreas Nathues, Kurt Mengel +7
We introduce an innovative three-dimensional spectral approach (three band parameter space with polyhedrons) that can be used for both qualitative and quantitative analyses improvi…
Moving towards high-power thin-disk lasers in the 2-μm wavelength range
Sergei Tomilov, Martin Hoffmann, Yicheng Wang +1
Thin-disk lasers (TDLs) have made spectacular progress in the last decades both in continuous-wave and ultrafast operation. Nowadays, single thin-disk oscillators with > 16 kW of c…
Photometric Properties of Ceres from Telescopic Observations using Dawn Framing Camera Color Filters
Vishnu Reddy, Jian-Yang Li, Bruce L. Gary +7
The dwarf planet Ceres is likely differentiated similar to the terrestrial planets but with a water/ice dominated mantle and an aqueously altered crust. Detailed modeling of Ceres'…
Hybrid air-bulk multi-pass cell compressor for high pulse energies with full spatio-temporal characterization
Alan Omar, Martin Hoffmann, Geoffrey Galle +2
Multi-pass cell (MPC) compressors have proven to be the method of choice for compression of high average power long-pulse Yb lasers. Yet, generating sub-30 fs pulses at high pulse…