Schäffner D, Preuschoff T, Ristok S, Brozio L, Schlosser M, Giessen H, and Birkl G
Optics express [Opt Express] 2020 Mar 16; Vol. 28 (6), pp. 8640-8645.
We present a novel platform of optical tweezers which combines rapid prototyping of user-definable microlens arrays with spatial light modulation (SLM) for dynamical control of each associated tweezer spot. Applying femtosecond direct laser writing, we manufacture a microlens array of 97 lenslets exhibiting quadratic and hexagonal packing and a transition region between the two. We use a digital micromirror device (DMD) to adapt the light field illuminating the individual lenslets and present a detailed characterization of the full optical system. In an unprecedented fashion, this novel platform combines the stability given by prefabricated solid optical elements, fast reengineering by rapid optical prototyping, DMD-based real-time control of each focal spot, and extensive scalability of the tweezer pattern. The accessible tweezer properties are adaptable within a wide range of parameters in a straightforward way.
Zhang Y, Luo J, Xiong Z, Liu H, Wang L, Gu Y, Lu Z, Li J, and Huang J
Optics express [Opt Express] 2019 Oct 28; Vol. 27 (22), pp. 31956-31966.
A flexible and efficient strategy, digital micromirror devices (DMD) based multistep lithography (DMSL), is proposed to fabricate arrays of user-defined microstructures. Through the combination of dose modulation, flexible pattern generation of DMD, and high-resolution step movement of piezoelectrical stage (PZS), this method enables prototyping a board range of 2D lattices with periodic/nonperiodic spatial distribution and arbitrary shapes and the critical feature size is down to 600 nm. We further explore the use of DMSL to fabricate microlens array by combining with the thermal reflowing process. The square shape and hexagonal shape microlens with customized distribution are realized and characterized. The results indicate that the proposed DMSL can be a significant role in the microfabrication techniques for manufacturing functional microstructures array.
Optics letters [Opt Lett] 2019 Oct 15; Vol. 44 (20), pp. 4961-4964.
Successful implementation of a catheter-based imaging system relies on the integration of high-performance miniaturized distal end optics. Typically, compensation of chromatic dispersion, as well as astigmatism introduced by the device's sheath, can be addressed only by combining multiple optical elements, adversely impacting size and manufacturability. Here, we present a 300×300×800 μm 3 monolithic optic that provides high optical performances over an extended wavelength range (near UV-visible-IR) with minimal chromatic aberrations. The design of the optic, fully optimized using standard optical simulation tools, provides the ability to freely determine aperture and working distance. Manufacturing is cost effective and suited for prototyping and production alike. The experimental characterization of the optic demonstrates a good match with simulation results and performances well suited to both optical coherence tomography and fluorescence imaging, thus paving the way for high-performance multimodal endoscopy systems.
We present a new refraction-based approach to embed multiple images into a single volume structure rendered on a glass solid (3D crystal). Each of the images can only be revealed when looked at from the certain viewpoint. While configurations of viewing directions in conventional methods are limited, our method can compensate for refractive effects at glass surfaces regardless of the viewing directions and enable the viewing directions to be set more flexibly, even allowing for 180 ∘ opposite projection by leveraging refraction. These unique features are verified with prototyping of 3D crystals projecting multiple grey-scale images and numerical assessments. In addition, we present a color dynamic representation of our method with computer graphics to demonstrate the potential use of our method as a novel information service system.
Shanblatt ER, Sung Y, Gupta R, Nelson BJ, Leng S, Graves WS, and McCollough CH
Optics express [Opt Express] 2019 Feb 18; Vol. 27 (4), pp. 4504-4521.
We demonstrate a fast, flexible, and accurate paraxial wave propagation model to serve as a forward model for propagation-based X-ray phase contrast imaging (XPCI) in parallel-beam or cone-beam geometry. This model incorporates geometric cone-beam effects into the multi-slice beam propagation method. It enables rapid prototyping and is well suited to serve as a forward model for propagation-based X-ray phase contrast tomographic reconstructions. Furthermore, it is capable of modeling arbitrary objects, including those that are strongly or multi-scattering. Simulation studies were conducted to compare our model to other forward models in the X-ray regime, such as the Mie and full-wave Rytov solutions.
Optics letters [Opt Lett] 2018 Nov 01; Vol. 43 (21), pp. 5347-5350.
This Letter describes the design, production, and characterization of a 1×2 arrayed waveguide grating (AWG) for fiber Bragg grating (FBG) readout, centered at 850 nm, with a channel spacing of 1 nm. The employed manufacturing process is laser direct lithography, a low-cost, rapid-prototyping capable, maskless method that allows for short iteration cycles and simple migration of a successful design to mask-based high throughput methods. We also consider the achievable AWG performance if used for strain or temperature measurements with FBG sensors.
Rapid prototyping (RP) techniques allow the construction of complex and sophisticated physical models based on personal needs, and the applications of the produced objects can be greatly extended by functionalizing the raw materials (e.g., resins) with components showing electrical, optical and magnetic properties. Here, we demonstrate a simple method for the realization of a three-dimensional architecture through 3D printing of organic resin doped with inorganic upconversion (UC) nanoparticles by using stereolithography technique. In our process, the wet-chemistry derived NaYF 4 : RE (RE: rare earth) nanoparticles with red, green and blue UC emission were incorporated into a resin matrix. We printed out pre-designed 3D structures with high precision and examined the UC emission properties. In a proof-of-concept experiment, we demonstrate that the 3D printed objects have reliable optical anti-counterfeiting based on high concealment in daylight and multi-color UC emission excited by a near-infrared laser at 980 nm. We also show that the 3D part with UC emission can be used for ratiometric temperature sensing from 303.15 K to 463.15 K, making it possible to map the temperature distribution for studying the thermal diffusion process in complex objects.
Prototyping of fiber-coupled integrated photonic devices requires robust and reliable way of docking optical fibers to other structures, often with sub-micron accuracy. We have developed an optical fiber micro-connector 3D-printed with Direct Laser Writing on a planar substrate. The connector provides fiber core precision positioning better than 120 nm and sustains cryogenic cycling without any signs of degradation. It can be fabricated and used on glass and non-transparent substrates, including photonic integrated circuits, semiconductor samples, and microfluidic systems.
We propose a new type of lensless camera enabling light-field imaging for focusing after image capture and show its feasibilities with some prototyping. The camera basically consists only of an image sensor and Fresnel zone aperture (FZA). Point sources making up the subjects to be captured cast overlapping shadows of the FZA on the sensor, which result in overlapping straight moiré fringes due to multiplication of another virtual FZA in the computer. The fringes generate a captured image by two-dimensional fast Fourier transform. Refocusing is possible by adjusting the size of the virtual FZA. We found this imaging principle is quite analogous to a coherent hologram. Not only the functions of still cameras but also of video cameras are confirmed experimentally by using the prototyped cameras.
Optics express [Opt Express] 2018 Jan 22; Vol. 26 (2), pp. 1497-1505.
We demonstrate for the first time functional arrayed waveguide gratings (AWGs) fabricated using the femtosecond laser direct-write technique. This fabrication technique is a mask-less alternative to lithography enabling design flexibility and rapid prototyping. It is ideal for customized small scale production for new applications. The devices were demonstrated in the visible region at 632.8 nm with a measured free spectral range (FSR) of 22.2 nm, and 1.35 nm resolution. To highlight the advantages of using a 3-dimensional fabrication technique, a 3-port photonic lantern was integrated with an AWG in a single monolithic chip. Integration of this type is not feasible with lithography-based AWG fabrication and can increase the functionality of AWGs for sensing applications.
We report a facile and direct fabrication method for integrating functional optical microstructures on the top surface of an optical fiber. A programmable maskless fabrication system was developed by using digital micromirror device (DMD), which allows rapid prototyping and low-cost fabrication without physical photomask. This maskless UV exposure system has the spatial resolution of 2.2 μm for an exposed area of 245 μm x 185 μm. Diverse optical microstructures were photolithographically defined on multimode fibers and a single mode optical fiber serially spliced with a coreless silica fiber segment. This method provides a new route for developing compact functional fiber-optic applications such as laser scanning, biosensing, or laser endomicroscopy.
Brenner P, Bar-On O, Siegle T, Leonhard T, Gvishi R, Eschenbaum C, Kalt H, Scheuer J, and Lemmer U
Applied optics [Appl Opt] 2017 May 01; Vol. 56 (13), pp. 3703-3708.
We demonstrate the realization of 3D whispering-gallery-mode (WGM) microlasers by direct laser writing (DLW) and their replication by nanoimprint lithography using a soft mold technique ("soft NIL"). The combination of DLW as a method for rapid prototyping and soft NIL offers a fast track towards large scale fabrication of 3D passive and active optical components applicable to a wide variety of materials. A performance analysis shows that surface-scattering-limited Q-factors of replicated resonators as high as 1×105 at 635 nm can be achieved with this process combination. Lasing in the replicated WGM resonators is demonstrated by the incorporation of laser dyes in the target material. Low lasing thresholds in the order of 15 kW/cm2 are obtained under ns-pulsed excitation.
Hosek J, Havran V, Nemcova S, Bittner J, and Cap J
Applied optics [Appl Opt] 2017 Feb 01; Vol. 56 (4), pp. 1183-1193.
Recent developments in optoelectronics and material processing techniques make it possible to design and produce a portable and compact measurement instrument for bidirectional texture function (BTF). Parallelized optics, on-board data processing, rapid prototyping, and other nonconventional production techniques and materials were the key to building an instrument capable of in situ measurements with fast data acquisition. We designed, built, and tested a prototype of a unique portable and compact multi-camera system for BTF measurement which is capable of in situ measurement of temporally unstable samples. In this paper, we present its optomechanical design.
Optics express [Opt Express] 2016 Nov 28; Vol. 24 (24), pp. 27077-27086.
Two photon polymerization (TPP) is a precise, reliable, and increasingly popular technique for rapid prototyping of micro-scale parts with sub-micron resolution. The materials of choice underlying this process are predominately acrylic resins cross-linked via free-radical polymerization. Due to the nature of the printing process, the derived parts are only partially cured and the corresponding mechanical properties, i.e. modulus and ultimate strength, are lower than if the material were cross-linked to the maximum extent. Herein, post-print curing via UV-driven radical generation, is demonstrated to increase the overall degree of cross-linking of low density, TPP-derived structures.
Recent developments in computational photography enabled variation of the optical focus of a plenoptic camera after image exposure, also known as refocusing. Existing ray models in the field simplify the camera's complexity for the purpose of image and depth map enhancement, but fail to satisfyingly predict the distance to which a photograph is refocused. By treating a pair of light rays as a system of linear functions, it will be shown in this paper that its solution yields an intersection indicating the distance to a refocused object plane. Experimental work is conducted with different lenses and focus settings while comparing distance estimates with a stack of refocused photographs for which a blur metric has been devised. Quantitative assessments over a 24 m distance range suggest that predictions deviate by less than 0.35 % in comparison to an optical design software. The proposed refocusing estimator assists in predicting object distances just as in the prototyping stage of plenoptic cameras and will be an essential feature in applications demanding high precision in synthetic focus or where depth map recovery is done by analyzing a stack of refocused photographs.
A new laser galvanometric scanning optical system incorporating a dynamic-tilt focusing lens is proposed to improve the laser spot performance in adaptive manufacturing applications. The simulations focus specifically on the laser spot size, the spot profile, the spot position, the spot energy distribution, and the size of the scanning working field. It is shown that for a designed spot size of 50 μm, the proposed system achieves an average spot size of 50.5 μm. Moreover, the maximum position deviation of the laser beam is reduced from (x=-3.02%, y=1.30%) in a traditional scanning system to (x=-0.055%, y=0.162%) in the proposed system. Finally, the maximum working field area is increased by around 240% compared to that of a traditional system. Overall, the results show that the proposed laser galvanometric scanning system achieves a small spot size, a symmetrical and round spot profile, a uniform spot energy distribution, and a large working area. As a result, it is ideally suited to rapid prototyping applications.
Leonhard N, Berlich R, Minardi S, Barth A, Mauch S, Mocci J, Goy M, Appelfelder M, Beckert E, and Reinlein C
Optics express [Opt Express] 2016 Jun 13; Vol. 24 (12), pp. 13157-72.
We explore adaptive optics (AO) pre-compensation for optical communication between Earth and geostationary (GEO) satellites in a laboratory experiment. Thus, we built a rapid control prototyping breadboard with an adjustable point-ahead angle where downlink and uplink can operate both at 1064 nm and 1550 nm wavelength. With our real-time system, beam wander resulting from artificial turbulence was reduced such that the beam hits the satellite at least 66% of the time as compared to merely 3% without correction. A seven-fold increase of the average Strehl ratio to (28 ± 15)% at 18 μrad point-ahead angle leads to a considerable reduction of the calculated fading probability. These results make AO pre-compensation a viable technique to enhance Earth-to-GEO optical communication.
Aieta F, Morovič P, Morovič J, Fiorentino M, Santori C, and Fattal D
Journal of the Optical Society of America. A, Optics, image science, and vision [J Opt Soc Am A Opt Image Sci Vis] 2016 Jun 01; Vol. 33 (6), pp. 1133-40.
The ability to display a broad variety of colors has great benefits not only in the context of entertainment but also as a means to streamline design in prototyping and manufacturing processes. Displays that use RGB filters or backlights cannot span all colors that occur in nature. To improve the accuracy of color reproduction, there have been attempts to include additional color primaries in displays. Existing solutions, however, have an impact on cost, scalability, and spatial resolution and are predominantly applicable to projection systems. We propose an approach based on combining diffraction grating extractors and the HANS imaging pipeline initially developed for printing. This combination offers unprecedented potential to attain large color gamuts with the same backlights commercially used today.
Nelson G, Kirian RA, Weierstall U, Zatsepin NA, Faragó T, Baumbach T, Wilde F, Niesler FB, Zimmer B, Ishigami I, Hikita M, Bajt S, Yeh SR, Rousseau DL, Chapman HN, Spence JC, and Heymann M
Optics express [Opt Express] 2016 May 30; Vol. 24 (11), pp. 11515-30.
Reliable sample delivery is essential to biological imaging using X-ray Free Electron Lasers (XFELs). Continuous injection using the Gas Dynamic Virtual Nozzle (GDVN) has proven valuable, particularly for time-resolved studies. However, many important aspects of GDVN functionality have yet to be thoroughly understood and/or refined due to fabrication limitations. We report the application of 2-photon polymerization as a form of high-resolution 3D printing to fabricate high-fidelity GDVNs with submicron resolution. This technique allows rapid prototyping of a wide range of different types of nozzles from standard CAD drawings and optimization of crucial dimensions for optimal performance. Three nozzles were tested with pure water to determine general nozzle performance and reproducibility, with nearly reproducible off-axis jetting being the result. X-ray tomography and index matching were successfully used to evaluate the interior nozzle structures and identify the cause of off-axis jetting. Subsequent refinements to fabrication resulted in straight jetting. A performance test of printed nozzles at an XFEL provided high quality femtosecond diffraction patterns.
Perraud JB, Obaton AF, Bou-Sleiman J, Recur B, Balacey H, Darracq F, Guillet JP, and Mounaix P
Applied optics [Appl Opt] 2016 May 01; Vol. 55 (13), pp. 3462-7.
Additive manufacturing (AM) technology is not only used to make 3D objects but also for rapid prototyping. In industry and laboratories, quality controls for these objects are necessary though difficult to implement compared to classical methods of fabrication because the layer-by-layer printing allows for very complex object manufacturing that is unachievable with standard tools. Furthermore, AM can induce unknown or unexpected defects. Consequently, we demonstrate terahertz (THz) imaging as an innovative method for 2D inspection of polymer materials. Moreover, THz tomography may be considered as an alternative to x-ray tomography and cheaper 3D imaging for routine control. This paper proposes an experimental study of 3D polymer objects obtained by additive manufacturing techniques. This approach allows us to characterize defects and to control dimensions by volumetric measurements on 3D data reconstructed by tomography.