Heterodyne standing-wave interferometer with improved phase stability. - In: Nanomanufacturing and metrology, ISSN 2520-8128, Bd. 4 (2021), 3, S. 190-199
This paper describes a standing-wave interferometer with two laser sources of different wavelengths, diametrically opposed and emitting towards each other. The resulting standing wave has an intensity profile which is moving with a constant velocity, and is directly detected inside the laser beam by two thin and transparent photo sensors. The first sensor is at a fixed position, serving as a phase reference for the second one which is moved along the optical axis, resulting in a frequency shift, proportional to the velocity. The phase difference between both sensors is evaluated for the purpose of interferometric length measurements.
https://doi.org/10.1007/s41871-021-00098-3
Matched coordinates for the analysis of 1D gratings. - In: Journal of the Optical Society of America, ISSN 1520-8532, Bd. 38 (2021), 6, S. 790-798
The Fourier modal method (FMM) is certainly one of the most popular and general methods for the modeling of diffraction gratings. However, for non-lamellar gratings it is associated with a staircase approximation of the profile, leading to poor convergence rate for metallic gratings in TM polarization. One way to overcome this weakness of the FMM is the use of the fast Fourier factorization (FFF) first derived for the differential method. That approach relies on the definition of normal and tangential vectors to the profile. Instead, we introduce a coordinate system that matches laterally the profile and solve the covariant Maxwells equations in the new coordinate system, hence the name matched coordinate method (MCM). Comparison of efficiencies computed with MCM with other data from the literature validates the method.
https://doi.org/10.1364/JOSAA.422374
Untersuchungen zur Positioniergenauigkeit der NanoFabrikationsmaschine (NFM-100) :
Investigations on the positioning accuracy of the Nano Fabrication Machine (NFM-100). - In: Technisches Messen, ISSN 2196-7113, Bd. 88 (2021), 9, S. 581-589
This contribution deals with the analysis of the positioning accuracy of a new Nano Fabrication Machine. This machine uses a planar direct drive system and has a positioning range up to 100 mm in diameter. The positioning accuracy was investigated in different movement scenarios, including phases of acceleration and deceleration. Also, the target position error of certain movements at different positions of the machine slider is considered. Currently, the NFM-100 is equipped with a tip-based measuring system. This Atomic Force Microscope (AFM) uses self-actuating and self-sensing microcantilevers, which can be used also for Field-Emission-Scanning-Probe-Lithography (FESPL). This process is capable of fabricating structures in the range of nanometres. In combination with the NFM-100 and its positioning range, nanostructures can be analysed and written in a macroscopic range without any tool change. However, the focus in this article is on the measurement and positioning accuracy of the tip-based measuring system in combination with the NFM-100 and is verified by repeated measurements. Finally, a linescan, realised using both systems, is shown over a long range of motion of 30 mm.
https://doi.org/10.1515/teme-2021-0079
Two-photon direct laser writing beyond the diffraction limit using the nanopositioning and nanomeasuring machine. - In: Nanomanufacturing and metrology, ISSN 2520-8128, Bd. 4 (2021), 3, S. 149-155
Since the first realization of two-photon direct laser writing (DLW) in Maruo et al. (Opt Lett 22:132-134, 1997), the manufacturing using direct laser writing techniques spread out in many laboratories all over the world. Photosensitive materials with different material properties open a new field for micro- and nanofabrication. The achievable structuring resolution using this technique is reported to be sub-100 nm (Paz et al. in J. Laser Appl. 24:042004, 2012), while a smallest linewidth of 25 nm could be shown in Tan et al. (Appl Phys Lett 90:071106, 2007). In our approach, the combination of DLW with the nanopositioning and nanomeasuring machine NMM-1 offers an improvement of the technique from the engineering side regarding the ultra-precise positioning (Weidenfeller et al. in Adv Fabr Technol Micro/Nano Opt Photon XI 10544:105440E, 2018). One big benefit besides the high positioning resolution of 0.1 nm is offered by the positioning range of 25 mm × 25 mm × 5 mm (Jäger et al. in Technisches Messen 67:319-323, 2000; Manske et al. in Meas Sci Technol 18:520-527, 2007). Thus, a trans-scale fabrication without any stitching or combination of different positioning systems is necessary. The immense synergy between the highly precise positioning and the DLW is demonstrated by the realization of resist lines and trenches whose center-to-center distance undergoes the modified diffraction limit for two-photon processes. The precise positioning accuracy enables a defined distance between illuminated lines. Hence, with a comparable huge width of the trenches of 1.655 [my]m due to a low effective numerical aperture of 0.16, a resist line of 30 nm between two written trenches could be achieved. Although the interrelationships for achieving such narrow trenches have not yet been clarified, much smaller resist lines and trench widths are possible with this approach in the near future.
https://doi.org/10.1007/s41871-021-00100-y
Self-heating of resistance thermometers for air temperature measurements with pulsed current supply :
Eigenerwärmung von Widerstandsthermometern für Lufttemperaturmessungen bei Impulstromspeisung. - In: Technisches Messen, ISSN 2196-7113, Bd. 88 (2021), 9, S. 556-561
Sehr präzise Lufttemperaturmessung in der Meteorologie oder in klimatisierten Innenräumen sind herausfordernd, weil Strahlungseinflüsse und die Eigenerwärmung der Widerstandsthermometer teilweise erhebliche Störeinflüsse sind. In unserem Artikel betrachten wir eine spezielle Stromspeisung und weisen nach, dass diese die Eigenerwärmung auf unter ein Millikelvin reduzieren kann. Für einen typischen, für den Außeneinsatz in meteorologischen Wetterstationen geeigneten und üblichen Fühleraufbau erfolgen Simulationen der durch den gepulsten elektrischen Messstrom auftretenden statischen und dynamischen Eigenerwärmung. Der transiente Verlauf der Eigenerwärmung hängt stärker vom inneren Aufbau des Fühlers als vom Wärmeübergangskoeffizienten zur umgebenden ruhenden Luft ab. Die mittlere statische Eigenerwärmung aus einem stark vereinfachten Modell passt gut zum simulierten transienten Verlauf. Die Methode der Impulsstromspeisung hat sich durch die beschriebenen Simulationen als sehr effektiv zur Verringerung der Eigenerwärmung von Widerstandsthermometern erwiesen.
https://doi.org/10.1515/teme-2021-0032
Measurement uncertainty 2020 :
Messunsicherheit 2020. - In: Technisches Messen, ISSN 2196-7113, Bd. 88 (2021), 2, S. 59-60
https://doi.org/10.1515/teme-2021-0003
Fundamental investigations in the design of five-axis nanopositioning machines for measurement and fabrication purposes. - In: Nanomanufacturing and metrology, ISSN 2520-8128, Bd. 4 (2021), 3, S. 156-164
The majority of nanopositioning and nanomeasuring machines (NPMMs) are based on three independent linear movements in a Cartesian coordinate system. This in combination with the specific nature of sensors and tools limits the addressable part geometries. An enhancement of an NPMM is introduced by the implementation of rotational movements while keeping the precision in the nanometer range. For this purpose, a parameter-based dynamic evaluation system with quantifiable technological parameters has been set up and employed to identify and assess general solution concepts and adequate substructures. Evaluations taken show high potential for three linear movements of the object in combination with two angular movements of the tool. The influence of the additional rotation systems on the existing structure of NPMMs has been investigated further on. Test series on the repeatability of an NPMM enhanced by a chosen combination of a rotary stage and a goniometer setup are realized. As a result of these test series, the necessity of in situ position determination of the tool became very clear. The tool position is measured in situ in relation to a hemispherical reference mirror by three Fabry-Pérot interferometers. FEA optimization has been used to enhance the overall system structure with regard to reproducibility and long-term stability. Results have been experimentally investigated by use of a retroreflector as a tool and the various laser interferometers of the NPMM. The knowledge gained has been formed into general rules for the verification and optimization of design solutions for multiaxial nanopositioning machines.
https://doi.org/10.1007/s41871-021-00102-w
Picometer-scale positioning of a linear drive system via feedforward-feedback control. - In: 2021 IEEE International Conference on Mechatronics (ICM), (2021), insges. 6 S.
This paper deals with the controller design of a linear drive system with potential applications in picometer-scale positioning. The displacement is measured using a high-precision differential plane-mirror laser interferometer. However, this measured signal must be filtered for control purposes and performance validation. For tracing picometers, we adopt a model-based 2-DOF control architecture with a feedforward stage for model-following and a feedback stage for stabilization and compensation of constant disturbances. A straightforward way to deal with noise is to use a feedback controller based on estimated (and filtered) states, which can be generated by a Kalman-Bucy filter. The effectiveness of the presented control strategy is verified via real-time experimentation, where the overall control scheme allows positioning in the picometer level. Moreover, comparative tests in the frequency domain were conducted using the so-called PI-LQR feedback controller based on estimated states.
https://doi.org/10.1109/ICM46511.2021.9385699
Phase-modulated standing wave interferometer. - In: Micromachines, ISSN 2072-666X, Bd. 12 (2021), 4, 357, insges. 15 S.
The actual technical implementation of conventional interferometers is quite complex and requires manual manufacturing. In combination with the required construction space defined by the optical setup, their applications are limited to selected measuring tasks. In contrast, Standing Wave Interferometers (SWIs) offer an enormous potential for miniaturisation because of their simple linear optical setup, consisting only of a laser source, a measuring mirror and two transparent standing wave sensors for obtaining quadrature signals. The two sensors are located inside the measuring beam and therefore directly influence the length measurement. To reduce optical influences on the standing wave and avoid the need for an exact and long-term stable sensor-to-sensor-distance, a single sensor configuration was developed. There, a phase modulation is superimposed to the sensor signal by a forced oscillation of the measuring mirror. When the correct modulation stroke is applied, the resulting harmonics in the sensor signal are 90˚ phase-shifted to each other and can hence be used for obtaining quadrature signals for phase demodulation and direction discrimination by an arctan-algorithm.
https://doi.org/10.3390/mi12040357
Magnetic behavior in commercial iron-silicon alloys controlled by the dislocation dynamics at temperatures below 420 K. - In: Journal of alloys and compounds, ISSN 1873-4669, Bd. 856 (2021), 157934
A decrease of the temperature dependent coercive forces up to around 370 K is discovered in iron silicon alloys, both in quenched samples and in samples which were previously thermally treated to achieve the highest magnetic quality. Alloys of composition Fe-6 wt.% Si and Fe-3 wt.% Si are studied. This reduction in the coercive force is controlled by an increase in the mobility of the domain walls due to the increase in the dislocation's mobility enhanced by the movement of vacancies. It is worthwhile to mention that this reduction in coercive force is only present at these slightly elevated temperatures which are markedly smaller than the usual annealing temperatures for heat treatment of iron silicon alloys while it disappears again at room temperature. Neutron thermodiffraction, magnetic hysteresis loops tracer and mechanical spectroscopy are used as experimental techniques.
https://doi.org/10.1016/j.jallcom.2020.157934