arXiv subjects

Lina Jäckering

Publications and source records attributed to Lina Jäckering.

4 recordsLinked to original sources

arXiv2026

Understanding inhomogeneous crystallization dynamics of phase-change materials in the vicinity of metallic nanoantennas

Optical metasurfaces composed of metallic or dielectric scatterers (meta-atoms) promise a powerful way of tailoring light-matter interactions. Phase-change materials (PCMs) are prime candidates for non-volatile resonance tuning of metasurfaces based on a refractive index change. Precise resonance control can be achieved by locally applying laser pulses to crystallize a PCM, modifying the dielectric surrounding of meta-atoms. However, the complex crystallization kinetics of PCMs in the vicinity of metallic meta-atoms have not been studied yet. Here, we experimentally investigate metallic dimer antennas on top of the PCM Ge3Sb2Te6 and address these nanoantennas with laser pulses. Our study reveals inhomogeneous crystallization caused by the absorption and heat conduction of the metallic nanoantennas. A self-consistent multiphysics model, including electromagnetic, thermal, and phase-transition processes, is employed to simulate the crystallization and understand the resulting resonance shift of the antennas. This model enables the optimization of the laser parameters and the geometry of the meta-atoms to achieve an optimal crystallization pattern and resonance shift. Our work paves the way towards complex antenna geometries optimized for local addressing of PCMs to achieve sophisticated crystallization patterns, enabling on-demand programming of individual nanoantennas within metasurfaces.

physics.optics↗

arXiv2026

Fast Programming of In-Plane Hyperbolic Phonon Polariton Optics Through van der Waals Crystals using the Phase-Change Material In3SbTe2

The high directionality of hyperbolic phonon polaritons (HPhPs) has opened radically new ways to route and steer the flow of energy at the nanoscale. However, launching HPhPs requires fabricating efficient and precisely aligned polariton launching structures, which remains time-consuming and expensive with conventional nanofabrication approaches. Recently, using optical laser pulses, polariton launching structures have been programmed into the plasmonic phase-change material In3SbTe2. Here, we leverage this approach to reconfigure HPhPs by programming a variety of launching and confining nanostructures through α-MoO3 flakes deposited onto In3SbTe2. Importantly, optical programming after flake deposition enables alignment of launching stripes to the [001]-axis of the flake, essential to control the directional polariton propagation. We showcase these capabilities in a variety of structures: i) an optically programmed disk, showing similar tuning ranges and confinement as focusing by gold disks; and ii) a cavity for in-plane HPhPs created by reconfiguring the single disk to a double disk structure, tailoring the confinement by simply reprogramming the disk distance. Our fabrication scheme offers fast turn-around times, flexible alignment and the opportunity to reconfigure the structures. Thus, it is a fast, efficient and versatile way to tailor propagation and confinement of highly directional polaritons on demand.

physics.optics↗

arXiv2025

Tailoring hBN's Phonon Polaritons with the Plasmonic Phase-Change Material In3SbTe2

Polaritons in van-der-Waals materials (vdWM) promise high confinement and multiple tailoring options by optical structures, e.g., resonators, launching structures and lenses. These optical structures are conventionally fabricated using cumbersome multi-process lithography techniques. In contrast, phase-change materials (PCMs) offer fast and reconfigurable programming of optical structures. PCMs can reversibly be switched between two stable phases with distinct permittivities by local heating, e.g., by optical laser pulses. While the well-known dielectric PCM GeSbTe-alloys feature only a permittivity change, the PCM In3SbTe2 can be switched between a dielectric and metallic phase. This makes In3SbTe2 promising for programming metallic launching structures. Here, we demonstrate direct optical programming and thereby rapid prototyping of optical launching structures in In3SbTe2 to tailor and confine polaritons in vdWM. We combine the vdWM hexagonal boron nitride (hBN) with In3SbTe2 and optically program circular resonators for hBN's phonon polaritons through hBN into In3SbTe2. We investigate the polariton resonators with near-field optical microscopy. Demonstrating the reconfigurability, we decrease the resonator diameter to increase the polariton confinement. Finally, we fabricate focusing structures for hBN's phonon polaritons whose focal point is changed in a second post-processing step. We promote In3SbTe2 as a versatile platform for rapid prototyping of polariton optics in vdWM.

physics.optics↗

arXiv2024

Super-resolution imaging of nanoscale inhomogeneities in hBN-covered and encapsulated few-layer graphene

Encapsulating few-layer graphene (FLG) in hexagonal boron nitride (hBN) can cause nanoscale inhomogeneities in the FLG, including changes in stacking domains and topographic defects. Due to the diffraction limit, characterizing these inhomogeneities is challenging. Recently, the visualization of stacking domains in encapsulated four-layer graphene (4LG) has been demonstrated with phonon polariton (PhP)-assisted near-field imaging. However, the underlying coupling mechanism and ability to image subdiffractional-sized inhomogeneities remain unknown. Here, we retrieve direct replicas and magnified images of subdiffractional-sized inhomogeneities in hBN-covered trilayer graphene (TLG) and encapsulated 4LG, enabled by the hyperlensing effect. This hyperlensing effect is mediated by hBN's hyperbolic PhP that couple to the FLG's plasmon polaritons. Using near-field microscopy, we identify the coupling by determining the polariton dispersion in hBN-covered TLG to be stacking-dependent. Our work demonstrates super-resolution and magnified imaging of inhomogeneities, paving the way for the realization of homogeneous encapsulated FLG transport samples to study correlated physics.

physics.optics↗