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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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[IEEE 2019 XXIX International Scientific Symposium "Metrology and Metrology Assurance" (MMA) - Sozopol, Bulgaria (2019.9.6-2019.9.9)] 2019 XXIX International Scientific Symposium "Metrology and Metrology Assurance" (MMA) - The metod of reducing measurement error of the propagation delays in optical elements and optical fibers
摘要： The paper presents a method of reducing the measurement error propagation delays of signals in optical elements and optical fibers, based on the approximation of the recorded form of optical pulses and determining the time intervals between pulses, using the values of the parameters of the approximating functions. The scheme of the installation implementing the proposed method is presented, as well as the results of experimental approbation of the method.
关键词： optical element,optical fiber,signal propagation delay,approximation
更新于2025-09-23 15:21:01
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Luminous Intensity Field Optimization for Antiglare LED Desk Lamp without Second Optical Element
摘要： This study proposes a model of a light module with an optimized luminous intensity ?eld for realizing an antiglare light-emitting diode (LED) desk lamp without a second optical element. We simulated di?erent luminous intensity ?eld pro?les to analyze the uni?ed glare rating (UGR) and illumination uniformity performance of a desk lamp. The spatial e?ect of UGR and the illumination uniformity a?ect eye comfort. The light module was set to di?erent beam angles without a second optical element, louver structure, and re?ective element on the luminaire to compare di?erent UGRs and uniformity values for evaluating human eye comfort. The simulation and experimental results indicated that the luminous intensity curve for a beam angle of 90? achieved an illumination uniformity of 80% and a UGR of 18.1 at a height of 45 cm, thus realizing a human-friendly antiglare desk lamp.
关键词： light-emitting diode,second optical element,uni?ed glare rating,desk lamp,antiglare
更新于2025-09-23 15:19:57
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Fiber coupling characteristics of holographic optical element for free-space optical communications
摘要： The use of a holographic optical element (HOE) is proposed as a substitute for the fine-pointing mechanism (FPM) in free-space optical communications. A HOE possessing a function to transform the propagation angle of the received beam to a designed direction is fabricated. The coupling characteristics of the received beam to a single-mode fiber are experimentally evaluated. The results confirm the potential of the proposed method and show the advantages over the FPM.
关键词： holographic optical element,free-space optical communications,fine-pointing mechanism,fiber coupling
更新于2025-09-19 17:13:59
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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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Fabrication of curved diffractive optical elements by means of laser direct writing, electroplating, and injection compression molding
摘要： In this work, a new process chain for the fabrication of curved micro-structured optical elements by injection compression molding is investigated. The fabrication is demonstrated for the example of a curved di?ractive optical element (DOE). In a ?rst process step a master substrate is fabricated using laser direct writing on a curved glass substrate. Blazed di?ractive micro-structures with lateral feature sizes down to 5 μm and height of 1.6 μm are created. A subsequent electroplating process is applied to create a nickel stamper to be used as a tool insert for the molding process. During electroplating, a 3 mm nickel layer is formed, transferring the di?ractive structures from the master substrate into a solid mold insert. The nickel stamper shows an accurate reproduction of the micro-structures. The mold insert is integrated into an injection compression molding tool to replicate the optical elements. Results show that the blazed di?ractive structures are replicated with a high quality. Tests of the components within a chromatic-confocal measurement setup con?rm that they can potentially replace expensive conventional elements.
关键词： Polymer optics,Injection compression molding,Laser direct writing,Di?ractive optical element
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
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Design of Curved Fresnel Lens with High Performance Creating Competitive Price Concentrator Photovoltaic
摘要： In this paper, the design of a curved Fresnel lens applying to the concentrator photovoltaic system is proposed by using the edge ray theorem, the Snell’s law, and the conservation of optical path length. The new structure of the curved Fresnel lens can improve significantly the uniformity of sunlight distribution over the solar cell while the concentration ratio can reach a high value of 900 times. The good uniform distribution can be obtained by using the novel idea. The novel idea is based on the uniform sunlight distribution of every groove of the lens so that the whole lens also distributes uniformly the sunlight beam over the receiver. The structure of the lens is built by two surfaces: input surface (or upper surface) as a part of spherical surface and output surface (or lower surface) that consists all grooves of the lens. Matlab program is used to design the input and the output surfaces of the lens. The input surface and the output surface are independent to each other in construction in Matlab. LighttoolsTM software is used to optimize the structure of the novel lens. Furthermore, LighttoolsTM is also used to perform a simulation to examine the efficiency of the lens in concentrator photovoltaic (CPV) system by using the light source with a wide spectrum of 380 – 1600 nm. The results show that the lens has an acceptance angle of 0.80 and good optical efficiency (>85%).
关键词： concentrator photovoltaic (CPV),Fresnel lens,solar energy,high concentration ratio,multi-junction solar cells,uniform irradiance distribution,CPV without secondary optical element (SOE)
更新于2025-09-12 10:27:22