Publications

DOI:

10.1002/lpor.202502341External link

University Bibliography Jena:

fsu_mods_00029702External link

Spectrally engineered multifrequency nanolasers are highly desirable for on-chip photonics, multiplexed biosensing, and display technologies, yet achieving them within a compact platform remains challenging. Here, we demonstrate multimode lasing from symmetry-broken TiO2 metasurfaces integrated with an SU8 slab waveguide containing rhodamine 6G. By coengineering guided-mode resonances, surface lattice resonances near Rayleigh anomalies, and quasi-bound states in the continuum, we realize complementary high-Q feedback pathways that overlap with the gain spectrum. The lasing emission direction is tailored through outcoupling via second-order Bragg diffraction and Rayleigh anomaly conditions, supporting both normal and oblique emission. Experiments reveal discrete lasing outputs across ≈100 nm bandwidth (548-648 nm), spanning the full rhodamine 6G emission band, with thresholds as low as ∼7 nJ (35.7 μJ/cm2) and up to four concurrent lasing peaks from a single device. These results establish a metasurface-dye platform for multifrequency and angle-selective lasing, opening new opportunities for compact, multifunctional nanophotonic sources.

DOI:

10.1021/acs.nanolett.5c06344External link

University Bibliography Jena:

fsu_mods_00035540External link

Photonic bound states in the continuum (BICs) have emerged as a versatile tool for enhancing light-matter interactions by strongly confining light fields. Chiral BICs are photonic resonances with a high degree of circular polarisation, which hold great promise for spin-selective applications in quantum optics and nanophotonics. Here, we demonstrate a novel application of a chiral BIC for inducing strong coupling between the circularly polarised photons and spin-polarised (valley) excitons (bound electron-hole pairs) in atomically-thin transition metal dichalcogenide crystals (TMDCs). By placing monolayer WS ₂ onto the BIC-hosting metasurface, we observe the formation of intrinsically chiral, valley-selective exciton polaritons, evidenced by circularly polarised photoluminescence (PL) at two distinct energy levels. The PL intensity and degree of circular polarisation of polaritons exceed those of uncoupled excitons in our structure by an order of magnitude. Our microscopic model shows that this enhancement is due to folding of the Brillouin zone creating a direct emission path for high-momenta polaritonic states far outside the light cone, thereby providing a shortcut to thermalisation (energy relaxation) and suppressing depolarisation. Moreover, while the polarisation of the upper polariton is determined by the valley excitons, the lower polariton behaves like an intrinsic chiral emitter with its polarisation fixed by the BIC. Therefore, the spin alignment of the upper and lower polaritons (↑↓ and ↑↑) can be controlled by σ ⁺ and σ − circularly polarised optical excitation, respectively. Our work introduces a new type of chiral light-matter quasi-particles in atomically-thin semiconductors and provides an insight into their energy relaxation dynamics.

DOI:

10.1038/s41467-026-70875-5External link

University Bibliography Jena:

fsu_mods_00035339External link

Selective control of the emission pattern of valley-polarized excitons in monolayer transition metal dichalcogenides is essential for advancing valleytronic, quantum information, and optoelectronic devices. Although substantial progress has been made in directionally routing photoluminescence from these materials, key challenges persist: specifically, establishing how observed routing effects relate to the degree of valley polarization and distinguishing genuine valley-dependent routing from spin-momentum coupling, an optical scattering effect unrelated to the emitter. In this work, we address these challenges by experimentally and numerically demonstrating a direct link between excitonic valley polarization and the resulting farfield emission pattern, enabling quantitative evaluation of valley-selective emission routing. We report valley-dependent manipulation of the angular emission pattern of monolayer tungsten diselenide using gold nanobar dimer antennas at cryogenic temperatures. By probing the emission under opposite circularly polarized excitation, we observe a valley-selective asymmetry in the photoluminescence circular dichroism of 2%. These measurements are supported by a reciprocity-based numerical framework that enables modeling of valley-selective emission in periodic systems. Our calculations further reveal that the observed valley-dependent directionality is a symmetry-protected property of the nanoantenna array arising from its extrinsic chirality at oblique emission angles, and that it can be substantially enhanced by tailoring the emitter distribution. Together, these results establish our nanoantenna platform as a robust route toward valleytronic signal processing.

DOI:

10.1021/acsnano.5c11672External link

University Bibliography Jena:

fsu_mods_00035715External link

Polarimetry with quantum light promises improved measurements for various scenarios. However, fundamental understanding of quantum photonic state transport in complex, real media, and tools to interpret the state after interaction with the sample are still lacking. Here, we theoretically and experimentally explore the evolution of polarization-entangled states in a turbid medium on example of tissue phantoms. By elaborating mathematical relationship between Wolf's coherency matrix and density matrix, we introduce a versatile framework describing the transfer of entangled photons in turbid environments with polarization tracking and resulting quantum state representation with the density operator. Experimentally, we reveal a robust trend in the state evolution depending on the reduced scattering coefficient of the medium. Our theoretical predictions correlate with experimental findings, while the model extends the study by photonic states with different degrees of entanglement. The presented results pave the way for quantitative quantum photonic sensing enabling applications ranging from biomedical diagnostics to remote sensing.

DOI:

10.1002/lpor.202501172External link

University Bibliography Jena:

fsu_mods_00029724External link

The mid-infrared (MIR) spectral region, spanning from 2- to 25- (Formula presented.), provides access to rich chemical information through the vibrational modes of functional groups, lipids, and other complex molecules. However, conventional imaging in this range remains limited by challenges in generating MIR light and by the lack of mature detection technologies. Quantum imaging with undetected light (QIUL) offers an alternative approach by using photon-pair sources in which the sample is illuminated with MIR light while detection and image reconstruction are carried out at visible wavelengths. We report the first QIUL technique that achieves diffraction-limited resolution without relying on spatial correlations of the photon-pair, thereby overcoming a fundamental limitation of all previous implementations. This work establishes induced coherence without induced emission as the essential physical resource underlying QIUL and redefines its operational boundary, extending its applicability to regimes where spatial correlations are weak or absent. Our results represent a conceptual advance in quantum imaging and open the way toward practical and cost-effective MIR microscopy based on visible detection.

DOI:

10.1002/lpor.202502356External link

University Bibliography Jena:

fsu_mods_00029626External link

Quasi-2D halide perovskites are chemically synthesized realizations of quantum well stacks with giant exciton oscillator strengths, tunable emission spectra, and very large exciton binding energies. While these features render quasi-2D halide perovskites a promising platform for room-temperature polaritonics, bosonic condensation and polariton lasing in quasi-2D perovskites have so far remained elusive at ambient conditions. Here, we demonstrate room-temperature cavity exciton-polariton condensation in mechanically exfoliated crystals of the quasi-2D Ruddlesden-Popper iodide perovskite (BA) ₂ (MA) ₂ Pb ₃ I ₁₀ in an open optical microcavity. We observe a polariton condensation threshold of 0.41 µJ cm −² per pulse and detect a strong non-linear response. Interferometric measurements confirm the spontaneous emergence of spatial coherence across the condensate with an associated first-order autocorrelation reaching 0.6 with 1 ps coherence time and an effective de Broglie wavelength of 13 µm. Our results lay the foundation for a new class of room-temperature polariton lasers based on quasi-2D halide perovskites with great potential for hetero-integration with other van-der-Waals materials and combination with photonic crystals or waveguides.

DOI:

10.1038/s41467-026-68723-7External link

University Bibliography Jena:

fsu_mods_00030276External link

The linear and third-order nonlinear optical response of thin-films of the transition metal dichalcogenide hafnium disulfide (HfS2) is investigated. Varying angle spectroscopic ellipsometry measurements are performed to obtain the material's in-plane and out-of-plane refractive indices in the – wavelength range. HfS2 is found to exhibit a strong, highly anisotropic linear optical response. In particular, it is shown that the material's in-plane refractive index exceeds a value of 3 throughout the visible wavelength range, while simultaneously offering a remarkably wide transparency window with for . The absolute value of the in-plane third-order nonlinear susceptibility is derived from third-harmonic generation (THG) measurements for fundamental wavelengths of to and is found to range from to, respectively. The obtained values significantly exceed those of conventional high-index materials, such as silicon or gallium phosphide. Furthermore, the efficiency of the THG process is found to be controllable by varying both the film thickness and the dielectric environment. These findings establish HfS2 as a highly promising candidate for nonlinear optical applications, surpassing the performance of conventional high-index materials.

DOI:

10.1002/adom.71164External link

University Bibliography Jena:

fsu_mods_00035724External link

3R-MoS ₂ , a MoS ₂ polytype with broken inversion symmetry, enables unique light-matter interactions and is promising for linear and nonlinear integrated photonics beyond the monolayer limit. Yet, systematic studies of its thickness-dependent reflectivity and its impact on harmonic generation are still lacking. While AFM can offer atomic-scale resolution, measuring 3R-MoS ₂ on non-solid substrates like PDMS remains challenging. To address this, a fast, non-destructive optical method is introduced to determine the thickness of 3R-MoS ₂ flakes from reflectivity measurements with a mean bias of less than 2 nm in the 3–200 nm range. Nonlinear characterization further reveals distinct thickness-dependent maxima in second- and third-harmonic generation (SHG/THG), with the first clear peak at ≈200 nm. These maxima arise from Fabry–Pérot-type phase matching conditions mediated by the film thickness and can further be shaped by absorption. This work thus provides both a practical thickness metrology and new insights for exploiting thickness-dependent 3R-MoS ₂ nonlinearities in scalable photonic technologies.

DOI:

10.1002/adom.202503498External link

University Bibliography Jena:

fsu_mods_00030234External link

DOI:

10.1109/CLEO/EUROPE-EQEC65582.2025.11109314External link

University Bibliography Jena:

fsu_mods_00027684External link

DOI:

10.1117/12.3058279External link

University Bibliography Jena:

fsu_mods_00026232External link

DOI:

10.1364/BODA.2025.JM4A.5External link

University Bibliography Jena:

fsu_mods_00026383External link