Publications

DOI:

10.1088/1681-7575/adbbf3External link

University Bibliography Jena:

fsu_mods_00022580External link

Gold gratings were measured by spectroscopic ellipsometry in reflection mode and modeled by the finite element method to investigate the capabilities of optical dimensional metrology for plasmonic diffractive structures. The gratings were prepared by electron beam lithography using parameters determined by finite element simulations for significant variations of the amplitude ratio and phase shift of the polarized reflection coefficients to achieve high sensitivity for both the measurement of the grating dimensions and the sensing capabilities. The sensitivity largely depends on the values in the five-dimensional parameter space including the grating parameters such as the critical dimension, the period, and the thickness of the grating, as well as the measurement parameters comprising the wavelength and the angle of incidence. The best limit of detection values are in the picometer range for the critical dimension and the thickness of the overlayer, and ≈10⁻⁵ for the refractive index.

DOI:

10.1021/acsomega.5c00951External link

University Bibliography Jena:

fsu_mods_00024130External link

To accurately achieve structure height differences in the range of single digit nanometres is of great importance for the fabrication of diffraction gratings for the extreme ultraviolet range (EUV). Here, structuring of silicon irradiated through a mask by a broad beam of helium ions with an energy of 30 keV was investigated as an alternative to conventional etching, which offers only limited controllability for shallow structures due to the higher rate of material removal. Utilising a broad ion beam allows for quick and cost effective fabrication. Ion fluence of the irradiations was varied in the range of 10¹⁶ ... 10¹⁷ ions · cm⁻². This enabled a fine tuning of structure height in the range of 1.00 ± 0.05 to 20 ± 1 nm, which is suitable for shallow gratings used in EUV applications. According to transmission electron microscopy investigations the observed structure shape is attributed to the formation of point defects and bubbles/cavities within the silicon. Diffraction capabilities of fabricated elements are experimentally shown at the SX700 beamline of BESSY II. Rigorous Maxwell solver simulation based on the finite-element method and rigorous coupled wave analysis are utilised to describe the experimental obtained diffraction pattern.

DOI:

10.1088/1361-6528/adc4ecExternal link

University Bibliography Jena:

fsu_mods_00023928External link

We report on the wafer scale fabrication of single-mode low-loss lithium niobate on insulator waveguides utilizing a chemically amplified resist and an optimized dry etching method. The fabricated single-mode waveguides are free of residuals and re-deposition, with measured losses for straight waveguides around 2 dB/m (0.02 dB/cm). We present a method offering advantages for large-scale production mainly due to its cost-effectiveness and faster writing time. This work holds promise for advancing integrated photonics and optical communication technologies.

DOI:

10.1364/OME.540146External link

University Bibliography Jena:

fsu_mods_00020928External link

DOI:

10.1088/1361-6528/add89aExternal link

University Bibliography Jena:

fsu_mods_00025176External link

We present the impact of line edge roughness (LER) on the optical critical dimension (OCD) metrology of nanostructures. The consideration of LER in OCD requires numerically expensive forward models and is therefore usually neglected. We present an analytical approach that allows estimation of the impact on the uncertainty. Systematic differences between CD measured by SEM and OCD were observed in different experiments. While SEM is basically sensitive to the local volume density, optical methods are sensitive to the permittivity of the material. We discuss an analytical upper bound on the contribution of the LER. For high index gratings, the contribution is as high as 3.7 nm for TM-polarized light and 1.2 nm for TE-polarized light, making this crucial for sub-nanometer metrology.

DOI:

10.1051/epjconf/202430902011External link

University Bibliography Jena:

fsu_mods_00018884External link

In the pursuit of closing the gap between nanometrology and nanofabrication, we investigate the use of advanced optical far field methods for sub-wavelength parameter reconstruction. With the goal of establishing a hybrid evaluation scheme connecting different methods and including different information channels, we performed comparison measurements on a silicon line grating sample with buried as well as not buried surface relief lines. To this end, the results of our measurement are in good agreements with each other, and the collected structure data is feasible to be used for hybrid evaluation.

DOI:

10.1051/epjconf/202430902005External link

University Bibliography Jena:

fsu_mods_00018883External link

Dielectric laser accelerators use near-infrared laser pulses to accelerate electrons at dielectric structures. Driving these devices with mid-infrared light should result in relaxed requirements on the electron beam, easier fabrication, higher damage threshold, and thus higher acceleration gradients. In this paper, we demonstrate dielectric laser acceleration of electrons driven with 10 µm light in a silicon dual pillar structure. We observe the acceleration of 27 keV electrons by 1.4 keV, corresponding to a 93 MeV/m acceleration gradient. The damage threshold of the structures of 3.3 ± 0.6 GV/m peak field is significantly higher than for near-infrared accelerators. The dual pillar acceleration structure itself even survived 5.2 ± 0.9 GV/m, the highest field strength we could achieve with the current system. This together with the larger structure acceptance bodes well for future dielectric laser accelerators driven with mid-infrared light.

DOI:

10.1364/OE.531071External link

University Bibliography Jena:

fsu_mods_00015789External link

DOI:

10.1117/12.3022706External link

University Bibliography Jena:

fsu_mods_00016232External link

Gold gratings were measured by spectroscopic ellipsometry and modeled by the finite element method to investigate the capabilities of optical dimensional metrology for plasmonic diffractive structures. The gratings were prepared by electron beam lithography using parameters determined by finite element simulations for significant variations of the amplitude ratio and phase shift of the polarized reflection coefficients to achieve high sensitivity for both the measurement of the grating dimensions and the sensing capabilities. Sub-nanometer sensitivity was shown to determine the grating dimensions and the thickness of an adsorbed layer to be detected in both traditional reflection and Kretschmann-Raether (KR) configurations. The sensitivity for the refractive index of the ambient was calculated to be 10−⁵ at best, which is not significantly better than the sensitivities for plane gold layers in KR configurations. However, in diffraction-based resonant setups, the high sensitivity dips can be shifted to a larger spectral range, which is highly significant in many applications. It was also revealed that 2D models assuming a perfect geometry fit the measured ellipsometry spectra only qualitatively, leaving room for model development in the future.

DOI:

10.1051/epjconf/202430902016External link

University Bibliography Jena:

fsu_mods_00018885External link

DOI:

10.1364/EUVXRAY.2024.JW4A.15External link

University Bibliography Jena:

fsu_mods_00017307External link

DOI:

10.1117/12.3018363External link

University Bibliography Jena:

fsu_mods_00017635External link