Efficient High-Refractive-Index Azobenzene Dendrimers Based on a Hierarchical Supramolecular Approach

Author(s):

Fusco, Sandra; Oscurato, Stefano Luigi; Salvatore, Marcella; Reda, Francesco; Moujdi, Sara; Oliveira, Michael De; Ambrosio, Antonio; Centore, Roberto & Borbone, Fabio

Abstract:

“Real-time manipulation of light in a diffractive optical element made with an azomaterial, through the light-induced reconfiguration of its surface based on mass transport, is an ambitious goal that may enable new applications and technologies. The speed and the control over photopatterning/reconfiguration of such devices are critically dependent on the photoresponsiveness of the material to the structuring light pattern and on the required extent of mass transport. In this regard, the higher the refractive index (RI) of the optical medium, the lower the total thickness and inscription time can be. In this work, we explore a flexible design of photopatternable azomaterials based on hierarchically ordered supramolecular interactions, used to construct dendrimer-like structures by mixing specially designed sulfur-rich, high-refractive-index photoactive and photopassive components in solution. We demonstrate that thioglycolic-type carboxylic acid groups can be selectively used as part of a supramolecular synthon based on hydrogen bonding or readily converted to carboxylate and participate in a Zn(II)–carboxylate interaction to modify the structure of the material and fine-tune the quality and efficiency of photoinduced mass transport. Compared with a conventional azopolymer, we demonstrate that it is possible to fabricate high-quality, thinner flat diffractive optical elements to reach the desired diffraction efficiency by increasing the RI of the material, achieved by maximizing the content of high molar refraction groups in the chemical structure of the monomers.”

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Publication: Chemistry of Materials
Issue/Year: Chemistry of Materials, 2023
DOI: 10.1021/acs.chemmater.3c00550

Multi-Bessel Beams Generated by an Axicon and a Spatial Light Modulator for Drilling Applications

Author(s):

Lutz, Christian; Schwarz, Simon; Marx, Jan; Esen, Cemal & Hellmann, Ralf

Abstract:

“We report on an optical setup to generate multi-Bessel beam profiles combining a refractive axicon and a spatial light modulator. Based on their particular beam profile, Bessel beams offer advantageous properties for micro drilling processes and internal volume processing, especially for transparent materials. In addition, the laser power of industrial, ultrashort pulsed lasers has increased significantly over the last few years, offering the possibility for highly efficient processes
using multi-spot profiles. Our optical concept combines the dynamic possibilities of beam splitting using a spatial light modulator with the benefits of Bessel beams, which facilitates multi-Bessel beam processing. Beside the simulation and experimental evaluation of the generated multi-Bessel beams, we exemplify the applicability of the developed module for the perforation of thin metal foils by micro drilling.”

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Publication: Photonics
Issue/Year: Photonics, Volume 10; Number 4; Pages 413; 2023
DOI: 10.3390/photonics10040413

Multi-Focal Laser Direct Writing through Spatial Light Modulation Guided by Scalable Vector Graphics

Author(s):

Duan, Linhan; Zhu, Yueqiang; Bai, Haoxin; Zhang, Chen; Wang, Kaige; Bai, Jintao & Zhao, Wei

Abstract:

“Multi-focal laser direct writing (LDW) based on phase-only spatial light modulation (SLM) can realize flexible and parallel nanofabrication with high-throughput potential. In this investigation, a novel approach of combining two-photon absorption, SLM, and vector path-guided by scalable vector graphics (SVGs), termed SVG-guided SLM LDW, was developed and preliminarily tested for fast, flexible, and parallel nanofabrication. Three laser focuses were independently controlled with different paths, which were optimized according to the SVG to improve fabrication and promote time efficiency. The minimum structure width could be as low as 81 nm. Accompanied by a translation stage, a carp structure of 18.10 μm × 24.56 μm was fabricated. This method shows the possibility of developing LDW techniques toward fully electrical systems, and provides a potential way to efficiently engrave complex structures on nanoscales.”

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Publication: Micromachines
Issue/Year: Micromachines, Volume 14; Number 4; Pages 824; 2023
DOI: 10.3390/mi14040824

Modeling of laser beam shaping by volume holographic phase masks

Author(s):

Vashchenko, Elena Shirshneva; Mohammadian, Nafiseh; Divliansky, Ivan & Glebov, Leonid

Abstract:

“Laser material processing applications often require the flat-top beam profile within focal spots ranged below 100 μm. For high power applications, volume phase masks recorded in photo- thermo-refractive glass (PTR) are promising. The problem is how to achieve simultaneously a high-quality shape and a small size of the beam. The commercial phase masks usually show large power losses in the beam wings, only about 40% of the energy was concentrated under the 95% level. By applying a gray phase mask instead of binary mask, one can reduce losses in the wings of the beam. In this work, a spatial light modulator (SLM) with designed computer generated holograms (CGHs) was used as a beam converter. Using the SLM with programmed gray mask allows obtaining flexible laser beam shaping, but beam quality is limited by imposed parameters of the SLM. The requirements for obtaining a square flat-top beam with energy lost in wings less than 10% is described. It was found that for sharp edges of the square flat-top beam, it is necessary that the size of the output beam contains at least 16 pixels of SLM. This fact is a consequence of the Fourier transform, where high spatial frequencies are responsible for the shape. The concept design of the scanning progressive mechanism of the master volume phase mask recording to exclude the influence of SLM work area dimensions is discussed.”

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Publication: Proc. SPIE 12402
Issue/Year: Proc. SPIE 12402, Components and Packaging for Laser Systems IX, 124020A, 2023
DOI: 10.1117/12.2651281

Color optimization of a full-color holographic stereogram printing system using a single SLM based on iterative exposure control

Author(s):

Khuderchuluun, Anar; Dashdavaa, Erkhembaatar; Rupali, Shindae; Kwon, Ki-Chul; Kang, Hoonjong; Lee, Kwon-Yeon & Kim, Nam

Abstract:

“In this paper, color optimization of a full-color holographic stereogram printing system using a single SLM based on iterative exposure is proposed. First, an array of sub-holograms (hogels) is generated effectively within fast computergenerated integral imaging, and fully analyzed phase-modulation for red, green, and blue (RGB) channels of hogel. Then, the generated hogels are recorded into holographic material sequentially where SLM displays the R, G, and B channels of a single hogel via effectual exposure under synchronized control with three electrical shutters for RGB laser illumination to obtain verified color optimization. Numerical simulation and optical reconstructions are implemented.”

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Publication: Proc. SPIE
Issue/Year: Proc. SPIE 12445, Practical Holography XXXVII: Displays, Materials, and Applications, 124450A (8 March 2023)
DOI: 10.1117/12.2651038

Highly transparent wave front printed volume holograms realized by amplitude-modulated incoherent pre-illumination

Author(s):

Wilm, Tobias; Wieland, Max; Fiess, Reinhold & Stork, Wilhelm

Abstract:

“We present highly transparent, wave front printed volume holographic optical elements (vHOEs), realized with a new recording method based on the pre-illumination of incoherent light patterns. The introduced amplitudemodulated pattern illuminates a distinct area on the unexposed, photopolymer-based holographic recording material prior to the hologram recording sequence. The incoherent pre-illumination scheme enables a precise tuning of the material’s local photosensitivity without the formation of a holographic volume diraction grating. As a consequence, the pre-illumination exposure signicantly suppresses the formation of transparency diminishing structures in the material that are formed concurrently with the volume diraction grating during the hologram recording sequence. The pre-illumination component is integrated in an extended immersion-based wave front printing setup, which realizes vHOEs by sequentially recording single holographic elements in an array-like structure. A wide range of dierent recording congurations is enabled by our recording setup due to independent modulation of both wave fronts and the possibility to realize large o-axis recording angles. We introduce two hologram characterization methods, based on a diraction eciency and a slanted-edge method analysis, which are used to evaluate the implemented pre-illumination method and demonstrate signicant improvements to the see-through quality of the presented wave front recorded vHOEs.”

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Publication: Proc. SPIE 12445
Issue/Year: Proc. SPIE 12445, Practical Holography XXXVII: Displays, Materials, and Applications, 124450S, 2023
DOI: 10.1117/12.2647361

Focal beam structuring by triple mixing of optical vortex lattices

Author(s):

Stoyanov, Lyubomir; Maleshkov, Georgi; Stefanov, Ivan; Paulus, Gerhard G. & Dreischuh, Alexander

Abstract:

“On-demand generation and reshaping of arrays of focused laser beams is highly desired in many areas of science and technology. In this work, we present a versatile approach for laser beam structuring in the focal plane of a lens by triple mixing of square and/or hexagonal optical vortex lattices (OVLs). In the artificial far field the input Gaussian beam is reshaped into ordered arrays of bright beams with flat phase profiles. This is remarkable, since the bright focal peaks are surrounded by hundreds of OVs with their dark cores and two-dimensional phase dislocations. Numerical simulations and experimental evidences for this are shown, including a broad discussion of some of the possible scenarios for such mixing: triple mixing of square-shaped OVLs, triple mixing of hexagonal OVLs, as well as the two combined cases of mixing square-hexagonal-hexagonal and square-square-hexagonal OVLs. The particular ordering of the input phase distributions of the OV lattices on the used spatial light modulators is found to affect the orientation of the structures ruled by the hexagonal OVL. Reliable control parameters for the creation of the desired focal beam structures are the respective lattice node spacings. The presented approach is flexible, easily realizable by using a single spatial light modulator, and thus accessible in many laboratories.”

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Publication: Optical and Quantum Electronics
Issue/Year: Optical and Quantum Electronics, Volume 54; Number 1; 2021
DOI: 10.1007/s11082-021-03399-5

Metamachines of pluripotent colloids

Author(s):

Aubret, Antoine; Martinet, Quentin & Palacci, Jeremie

Abstract:

“Machines enabled the Industrial Revolution and are central to modern technological progress: A machine’s parts transmit forces, motion, and energy to one another in a predetermined manner. Today’s engineering frontier, building artificial micromachines that emulate the biological machinery of living organisms, requires faithful assembly and energy consumption at the microscale. Here, we demonstrate the programmable assembly of active particles into autonomous metamachines using optical templates. Metamachines, or machines made of machines, are stable, mobile and autonomous architectures, whose dynamics stems from the geometry. We use the interplay between anisotropic force generation of the active colloids with the control of their orientation by local geometry. This allows autonomous reprogramming of active particles of the metamachines to achieve multiple functions. It permits the modular assembly of metamachines by fusion, reconfiguration of metamachines and, we anticipate, a shift in focus of self-assembly towards active matter and reprogrammable materials.”

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Publication: Nature Communications
Issue/Year: Nature Communications, Volume 12; Number 1; 2021
DOI: 10.1038/s41467-021-26699-6

Laser beam shaping based on amplitude-phase control of a fiber laser array

Author(s):

Adamov, E. V.; Aksenov, V. P.; Atuchin, V. V.; Dudorov, V. V.; Kolosov, V. V. & Levitsky, M. E.

Abstract:

“A new technique is suggested for the generation of laser beams with an intensity profile specified. The technique is based on the coherent combining of radiation of a fiber laser array with adaptive control of the power and phase of Gaussian subbeams with plane wavefronts. The power and phase of the subbeams are determined for each intensity profile specified in the far field based on the inverse problem solution, for example, by the Gershberg–Saxton method. To form a required phase profile, the stochastic parallel gradient descent (SPGD) method is used along with the inversion of a required phase distribution with a phase corrector. The main advantages of the technique are the adaptive control of the intensity profile and a possibility of generating high-power laser beams. The results of numerical and field experiments are described.”

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Publication: OSA Continuum
Issue/Year: OSA Continuum, Volume 4; Number 1; Pages 182; 2021
DOI: 10.1364/osac.413956

Polymer Optical Waveguide Sensor Based on Fe-Amino-Triazole Complex Molecular Switches

Author(s):

Khan, Muhammad Shaukat; Farooq, Hunain; Wittmund, Christopher; Klimke, Stephen; Lachmayer, Roland; Renz, Franz & Roth, Bernhard

Abstract:

“We report on a polymer-waveguide-based temperature sensing system relying on switchable molecular complexes. The polymer waveguide cladding is fabricated using a maskless lithographic optical system and replicated onto polymer material (i.e., PMMA) using a hot embossing device. An iron-amino-triazole molecular complex material (i.e., [Fe(Htrz)2.85(NH2-trz)0.15](ClO4)2) is used to sense changes in ambient temperature. For this purpose, the core of the waveguide is filled with a mixture of core material (NOA68), and the molecular complex using doctor blading and UV curing is applied for solidification. The absorption spectrum of the molecular complex in the UV/VIS light range features two prominent absorption bands in the low-spin state. As temperature approaches room temperature, a spin-crossover transition occurs, and the molecular complex changes its color (i.e. spectral properties) from violet-pink to white. The measurement of the optical power transmitted through the waveguide as a function of temperature exhibits a memory effect with a hysteresis width of approx. 12 °C and sensitivity of 0.08 mW/°C. This enables optical rather than electronic temperature detection in environments where electromagnetic interference might influence the measurements”

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Publication: Polymers
Issue/Year: Polymers, Volume 13; Number 2; Pages 195; 2021
DOI: 10.3390/polym13020195
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