Publications

DOI:

10.1063/5.0315204External link

University Bibliography Jena:

fsu_mods_00035092External 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

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

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

Point defects in solid-state quantum systems are vital for enabling single-photon emission at specific wavelengths, making their precise identification essential for advancing applications in quantum technologies. However, pinpointing the microscopic origins of these defects remains a challenge. In this work, we propose Raman spectroscopy as a robust strategy for defect identification. Using density functional theory, we characterize the Raman signatures of 100 defects in hexagonal boron nitride (hBN) spanning periodic groups III to VI, encompassing around 30,000 phonon modes. Our findings reveal that the local atomic environment plays a pivotal role in shaping the Raman lineshape. Furthermore, we demonstrate that Raman spectroscopy can differentiate defects based on their spin and charge states as well as strain-induced variations. The ability to resolve spin configurations offers a pathway to identifying defects with spins suitable for quantum sensing. Finally, an experimental concept using tip-enhanced Raman spectroscopy has been proposed in this work. Therefore, this study not only provides a comprehensive theoretical database of Raman spectra for hBN defects but also establishes a novel experimental framework to identify point defects. More broadly, our approach offers a universal method for defect identification in any quantum materials with spin configurations specific to any quantum application.

DOI:

10.1038/s41524-025-01921-xExternal link

University Bibliography Jena:

fsu_mods_00029842External link

DOI:

10.1007/978-3-032-13852-1_12External link

University Bibliography Jena:

fsu_mods_00034732External link

The potential of color centers in hexagonal boron nitride (hBN) for quantum technology applications has driven research to create emitters across a broad spectral range by using diverse techniques. Electron beam irradiation is one such approach that creates yellow emitters at room temperature; however, their behavior at low temperatures remains unexplored. Here, we present a comprehensive photophysical characterization of these yellow emitters in hBN under cryogenic conditions. We identify a bright and photostable defect with a zero-phonon line (ZPL) at 547.5 nm and a phonon sideband (PSB) approximately 90 meV from the ZPL. Excitation through this PSB enhances the emission intensity by nearly 5-fold at 4.5 K. Temperature-dependent photoluminescence (PL) from 4.5 to 220 K shows a decreasing Debye–Waller (DW) factor with elevated temperature, reflecting enhanced phonon-assisted emission. Further analysis reveals the presence of an additional low-energy phonon mode, leading to a T ³ dependence of the ZPL line width and a T ² dependence of the ZPL peak shift. These observations deepen our understanding of the nature of the emitters, opening new avenues for the precise tuning of quantum light sources.

DOI:

10.1021/acsphotonics.5c02858External link

University Bibliography Jena:

fsu_mods_00034416External link

Shaped laser pulses have been remarkably effective in investigating various aspects of light–matter interactions spanning a broad range of research. Chirped laser pulses exhibiting a time-varying frequency, or quadratic spectral phase, form a crucial category in the group of shaped laser pulses. This type of pulses have made a ubiquitous presence from spectroscopic applications to developments in high-power laser technology, and from nanophotonics to quantum optical communication, ever since their introduction. In the case of quantum technologies recently, substantial efforts are being invested toward achieving a truly scalable architecture. Concurrently, it is important to develop methods to produce robust photon sources. In this context, semiconductor quantum dots hold great potential, due to their exceptional photophysical properties and on-demand operating nature. Concerning the scalability aspect of semiconductor quantum dots, it is advantageous to develop a simple, yet robust method to generate photon states from it. Chirped pulse excitation has been widely demonstrated as a robust and efficient state preparation scheme in quantum dots, thereby boosting its applicability as a stable photon source in a real-world scenario. Despite the rapid growth and advancements in laser technologies, the generation and control of chirped laser pulses can be demanding. Here, an overview of a selected few approaches is presented to tailor and characterize chirped pulses for the efficient excitation of a quantum dot source. By taking the chirped-pulse-induced adiabatic rapid passage process in quantum dot as an example, numerical design examples are presented along with experimental advantages and challenges in each method and conclude with an outlook on future perspectives.

DOI:

10.1002/qute.202300352External link

University Bibliography Jena:

fsu_mods_00009894External link

DOI:

10.1002/adem.202402930External link

University Bibliography Jena:

fsu_mods_00025547External link