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Scaling effects on the optical properties of patterned nano-layered shape memory films
摘要： Nano-layered films of PVAc/PU systems were fabricated by forced assembly coextrusion method. The bulk shape memory properties of PVAc/PU systems were utilized to program nanoscale patterns such as diffraction grating which exhibit iridescence after patterning. A hot embossing process has been utilized to imprint diffraction grating patterns as nano-scale information onto the surface of the thin multilayer films. Three levels of hierarchy i.e. layer thickness, spacing and heights of patterns, governs the functionality of the patterned multilayer film. The time and temperature dependent viscoelastic shape memory behavior determines the opto-mechanical tunability of the film. Mechanical switching of the patterns also leads to optical switching of the films which corresponds to their efficiency of information retrieval. The recovery of patterns as well as the diffractive property depends on the layer thickness (l) of films and heights of patterns (h0). The results illustrate that the higher ratio of h0/l better is the recovery of the grating patterns and the corresponding diffractive properties. This scaling effect enables versatile applications in information security by tuning the layer structure of the multilayer shape memory films.
关键词： scaling effect,shape memory film,pattern programming,hot embossing,multilayer film,information security,diffractive optical element,thermal responsive optics
更新于2025-10-22 19:40:53
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Testing of diffractive optical element as part of specific CO <sub/>2</sub> laser equipment for metallic materials modification
摘要： Testing of a reflective diffractive optical element (DOE) as part of specific CO2 laser equipment Oerlikon OPL 2000 for metallic materials modification was performed. The power density distribution in a plane located behind the DOE focal plane has been measured. It was found that DOEs make it possible to form a predetermined beam power density profile and to perform the transformation of laser energy, chosen by calculation previously. The use of these optical elements in the laser material treatment reveals new possibilities for controlling properties and operational characteristics of processed components. Additional redistribution of the beam power to edges of the laser spot is achieved by increasing the proportion of energy reflected by DOE peripheral zones, for example, by increasing the aperture of the focusable beam. It is proposed using a telescopic system of two lenses to change the aperture of the laser beam focusable by the DOE.
关键词： metallic materials modification,diffractive optical element,beam power density profile,CO2 laser
更新于2025-09-19 17:13:59
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[IEEE 2018 17th Workshop on Information Optics (WIO) - Québec, QC, Canada (2018.7.16-2018.7.19)] 2018 17th Workshop on Information Optics (WIO) - Grating-assisted spatial phase-shifting incoherent digital holography with compressive sensing for noise reduction
摘要： We have proposed grating-assisted spatial phase-shifting incoherent digital holography for capturing holograms of dynamically moving objects. With our method, four individual self-reference holograms of a spatially incoherent light are simultaneously created on an image sensor. Thus, it is possible to detect complex amplitude distribution from a single captured image by using a phase-shifting technique. In the present study, we aim to improve the quality of reconstructed images in our method by introducing compressive sensing. To validate the effectiveness of compressive sensing in our method, a 3D image was reconstructed from detected complex amplitude distribution by enforcing the sparsity constraint on the total variation of a signal. As a result, the introduction of compressive sensing can effectively reduce noise and out-of-focus artifacts in our method.
关键词： phase-shifting interferometer,3D imaging,diffractive optical element,compressive sensing,digital holography
更新于2025-09-16 10:30:52
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Ultra-fast laser micro processing by multiple laser spots
摘要： In the direct processing of three dimensional micro structures for surface functionalization, usp-lasers provide the necessary resolution and quality. The increasing resolution brings along a rising machining time which leads to the unavoidable demand of multiple spots. In this paper a newly developed high compact ps-laser with repetition rates of up to 8 MHz and an average power of 500 W was distributed by a diffractive element on a 16 channel acousto optical modulator that individually modulates each of the 16 spots. The typical laser based micro processing method was enhanced to reach a machining technology in which 16 different layers could be processed within one path. In a further step, 4 of these high compact beam deliveries could be integrated in one cylinder micro processing system to generate at least 64 individual acting laser spots. Different functional structures were processed and shown in this paper.
关键词： surface functionalization,Three dimensional micro strucutures,Mulit-Spot,Diffractive Optical Element DOE,usp-laser
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Increasing Two-Photon Polymerization Fabrication Speed of 3D Structures for Cell Interaction Studies
摘要： Expanding cell studies and tissue engineering from a 2D platform to a 3D mimic of their natural environment demands fabrication methods capable of creating scaffolds covering large volumes with feature sizes down to a few μm. Two-photon polymerization (TPP) is a direct writing method capable of fabricating free-form 3D structures with sub-wavelength features and is therefore well-suited for template fabrication for cell motility and tissue engineering. We demonstrate 9 times increased fabrication speed for 3D periodic structures using a diffractive optical element (DOE) that creates 9 beamlets from one femtosecond laser beam. The parallelized method maintains fabrication quality and each beamlet is used for the fabrication of the base structures that form the periodic pattern. Two 3D designs were fabricated from bio-compatible SZ2080 polymer, where the distance between structures are accurately matching the distance between beamlets. Both of the fabricated structure arrays consists of 3x3 patterns with 9 individual structures in each pattern and covers an area of 450x450 μm. The first design contains unsupported interconnections between individual structures and field-of-views (FOV’s). The second design contains additional supporting structures that stabilize those interconnections between individual structures and FOV’s. For the first design high similarity is observed between the individual base structures inside each FOV, while at the stitching positions between different FOV’s discrepancies are observed leading to gaps in the overall periodic pattern. The gaps arise from contraction of the polymer material during the development process and subsequently drying process. It is related to large leapfrog movement of the stage system (>150 μm) between FOV’s. In the second design, additional support was added between individual one voxel thin structures to overcome this problem. Using this strategy, no gaps are observed and any remaining mismatch is less than 100 nm for stitching of structures. Additional studies were performed where HeLa-cells were incubated for 24 hours on both scaffolds and cell affinity is studied. We observe in both cases that HeLa-cells attach to wall and corner segments of the periodic designs and furthermore HeLa-cells are seen stretching the full length of the individual wall segments. In summary, we show that parallelization of the fabrication process has the potential to make TPP a fast method for large volume periodic 3D structure.
关键词： Two-photon polymerization,cell interaction studies,fabrication speed,diffractive optical element,3D structures
更新于2025-09-12 10:27:22