Publications

DOI:

10.1063/5.0315204External link

University Bibliography Jena:

fsu_mods_00035092External link

Due to its properties and high purity, fused silica is an omnipresent material used in applications across nearly all fields of photonics and optics. However, the complex process chains involved in the manufacturing of precision optical components and systems made of Fused Silica are costly and time consuming. Laser-Assisted-Diamond-Turning (LADT) offers a flexible approach to machine hard and brittle materials like infrared crystals (e.g. silicon) as well as ceramics (e.g. silicon carbide) by combining ultra-precision turning (UP-turning) with laser radiation but isn’t fully developed for glasses. Understanding how temperature distributions evolve both over time and space is crucial, since the deposited energy is necessary to modify the mechanical properties on one side but also results in form deviations on the other. In this Paper, a test rig is presented for the in-situ evaluation of the process temperature. By utilizing microscopic thermal imaging, the peak temperature development can be visualized and contextualized with respect to relevant machining parameters like the cutting or feed speed. For validation purposes, the overheating effect in laser-assisted-turning processes has been investigated experimentally by irradiating fused silica with a CO2-Laser including realistic kinematic conditions. The findings demonstrate that implementing energy regulation mechanisms is essential during LADT of fused silica in order to avoid overheating in the central region of the component.

DOI:

10.1016/j.procir.2026.07.111External link

University Bibliography Jena:

fsu_mods_00039193External link

Processing transparent materials with ultrashort laser pulses (USP) provides significant advantages over conventional methods in various industrial applications, enabling precise energy deposition and controlled modification of the laser irradiated material. The present study investigates ablation-free surface structuring (microforming) of borosilicate glass (Borofloat 33, SCHOTT) using USP-laser (350 fs at a wavelength of 515 nm) in a scanning-based laser process. Irradiated areas ranged from 1 to 12 mm ² , with microformed structures produced on both top and bottom sample surfaces, reaching profile heights (peak-to-valley) of up to 20 µm. The analysis focuses on the relationship between temporal and spatial energy distribution and the ultra-fast cooling rate during USP laser treatment. It was found that ablation-free microforming is determined by the scanning strategy, the amount of energy absorbed, and the interaction volume, with the critical energy threshold for glass softening identified as crucial for controlled structuring. Characterization by white light interferometry, polarimetry, wavefront analysis, Raman spectroscopy, and thermography revealed structural changes in the glass network, including inhomogeneous density changes, measurable volume expansion within the irradiated areas and non-homogeneous residual stress distributions. These effects are found to be responsible for the formation of the modified surface topography.

DOI:

10.1002/adom.202503530External link

University Bibliography Jena:

fsu_mods_00035443External link

Sky-high optical nonlinearities make semiconductors ideal platforms for multifunctional photonic devices. The fabrication of such complex devices could greatly benefit from in-volume ultrafast laser writing for monolithic and contactless integration. Ironically, as exemplified for Si, nonlinearities act as an efficient immune system that self-protects the material from internal permanent modifications. Predicting high-intensity ultrashort-pulse propagation beyond Si is further limited by incomplete descriptions of carrier dynamics in narrow-gap materials. Here, we demonstrate that filamentation universally dictates ultrashort laser pulse propagation in various semiconductors. The effective key nonlinear parameters extracted differ markedly from past measurements with low-intensity pulses, while temporal scaling laws for these parameters are also derived. Based on these findings, appropriate temporal-spectral shaping is proposed for tailored energy deposition inside semiconductors. The effective parameters also provide predictive inputs for semiconductor backside processing, microelectronics security, and high-harmonic, supercontinuum and terahertz wave generation.

DOI:

10.1038/s41467-026-69530-wExternal link

University Bibliography Jena:

fsu_mods_00034334External link

Through-bulk columnar structures perpendicular to the surface of a 1 mm thick monocrystalline silicon sample are achieved using ultrashort pulsed laser radiation at a wavelength of around 1.6 μm. A range of pulse parameters is systematically investigated to evaluate the probability of column formation and to optimize column growth throughout the bulk of silicon. Fabrication is performed with a glass substrate as support below the sample and in air in order to assess the influence of substrate support on the modification probability. The results indicate that the absence of a support substrate promotes columnar growth over a wider range of parameter combinations compared to substrate-supported configurations, and that the transition from column formation to no column formation is transient with a probabilistic behavior of the modifications in the transition region. Furthermore, pulse duration is found to play a critical role for the modification probability such that the lack of permanent modification observed at 550 fs pulse duration can be mitigated by employing longer pulses of 2.5 ps. Under optimized writing conditions, continuous cylindrical columns with lengths of up to 1 mm can be produced at writing speeds up to 20 μm/s.

DOI:

10.1016/j.procir.2026.07.160External link

University Bibliography Jena:

fsu_mods_00039199External link

DOI:

10.1117/12.3080976External link

University Bibliography Jena:

fsu_mods_00036539External link

DOI:

10.1117/12.3089076External link

University Bibliography Jena:

fsu_mods_00035604External link

Coherent Raman scattering (CRS) techniques such as coherent anti-Stokes Raman scattering (CARS) provide chemically specific vibrational contrast with signal levels far exceeding spontaneous Raman scattering (SpRS). Extending these to broadband excitation enables multiplex detection across wide spectral regions, including the fingerprint region, CH-stretch bands and high-frequency vibrational modes. This review provides a structured overview of excitation architecture for broadband CRS, ranging from low-energy oscillator schemes to energy-scalable platforms. The discussion is organized along key design parameters, including spectral bandwidth, excitation intensity, and probe delay, which jointly determine the accessible operating regimes. Rather than representing competing methods, the reviewed architectures are presented as a complementary toolbox for application-driven spectroscopy in chemically reactive environments and complex biological systems. In addition, a representative OPCPA-based implementation is presented as a platform demonstration to illustrate accessible operating regimes, single-shot stability, and multiplex detection capability under realistic experimental conditions.

DOI:

10.3390/molecules31071207External link

University Bibliography Jena:

fsu_mods_00035658External link

DOI:

10.1117/12.3101256External link

University Bibliography Jena:

fsu_mods_00035603External link

A systematic exploration of amorphous ABC heterostructures revealed that nanoscale morphological modifications markedly improved their artificial bulk second-order susceptibility. These amorphous birefringent heterostructures were fabricated using plasma-enhanced atomic layer deposition of three oxides, thereby breaking centrosymmetry at the nanoscale. We observe that the optical nonlinearity depends on the thickness variation of the three constituent materials, SiO ₂ , TiO ₂ , and Al ₂ O ₃ , ranging from tens of nanometers to the atomic scale, and where the thin films exhibit second-order susceptibility at their interfaces. Our findings reveal that the enhancement of nonlinear optical properties is strongly correlated with a high interface density and superior interface quality, where the interface second-order nonlinearity transitions to bulk-like second-harmonic generation. An effective bulk second-order susceptibility of χ zzz = 2.0 ± 0.2 pm/V at 1032 nm is achieved, comparable to some conventional monocrystalline nonlinear materials.

DOI:

10.1364/OME.590548External link

University Bibliography Jena:

fsu_mods_00036144External link

Second harmonic (SH) radiation can only be generated in non-centrosymmetric bulk crystals under electric dipole approximation. Nonlinear thin films made from bulk crystals are technologically challenging because of complex and high-temperature fabrication processes. In this work, heterostructures made of two distinct amorphous materials, namely SiO ₂ and TiO ₂ , were prepared through plasma-enhanced atomic layer deposition (PEALD) with deposition temperature of 100 °C. By using the uniaxial dispersion model, we characterized the form birefringence of the deposited films, which can play a crucial role for the phase-matching condition in nonlinear waveguides or other nonlinear optical applications. By applying a fringe-based technique, we determined the largest diagonal component of the effective bulk second-order susceptibility, (Formula presented.) = 1.30 ± 0.13 pm/V, at a wavelength of 1032 nm. Noteworthy, we observed strong SHG signals from two-component nanolaminates, which are several orders of magnitude larger than those from single layers. The SHG signals from our samples only require the broken inversion symmetry at the interface. Here, optical properties of nanocomposites can be precisely engineered using the promising PEALD technology.

DOI:

10.3390/coatings16040424External link

University Bibliography Jena:

fsu_mods_00035974External link

Designing descriptors for multiple defects in two-dimensional materials is challenging due to the diverse local atomic environments created by different defect types and arrangements. Existing physics-informed descriptors struggle to distinguish distinct defect configurations with identical composition, while deep learning models, though powerful, require large data sets and are less interpretable. In this work, we address this limitation by engineering chemical descriptors and constructing structural features from nearest-neighbor distributions provided by the classical force-field-inspired descriptors (CFID). We show that our engineering method, combined with defect-aware structural features derived from the Hellinger distance, even excluding the full distribution features, improves data point discrimination in high-dimensional feature space while reducing the number of features by 50%. In predicting formation energy per defect site, this extended feature set balances reliance on a few dominant features, enhancing model interpretation and generalization at the cost of a marginal 10% increase in prediction error compared to baseline descriptors. This generalization capability is empirically validated on an external out-of-distribution data set of bulk hBN defects, where our model exhibits lower uncertainty and superior stability within the applicable physical domain (− 1 < E f < 5 eV). However, predicting a highly complex and nonlinear target, such as the HOMO–LUMO gap, remains challenging, as none of our extensions outperform the baseline. This physics-informed approach offers an interpretable and computationally efficient alternative to deep learning models, providing new insights into defect representations in 2D materials and serving as a tool for the high-throughput prescreening of stable defect candidates prior to expensive first-principles calculations.

DOI:

10.1021/acs.jcim.5c02100External link

University Bibliography Jena:

fsu_mods_00034454External link