Microchannels inside bulk PMMA generated by femtosecond laser using adaptive beam shaping

Author(s):

Roth, Gian-Luca; Rung, Stefan; Esen, Cemal & Hellmann, Ralf

Abstract:

“In this contribution, we report on the generation of internal microchannels with basically unlimited channel length inside of PMMA bulk material by femtosecond laser. A precisely controllable and stable circular channel cross section is obtained by using a spatial light modulator to compensate the writing depth depending spherical aberration. Furthermore, the generation of a rotatable elliptical input beam by adaptive optics ensures a fitting of the beam shaping to the writing direction. In this study, we report on both, the effect of the ellipticity of the input beam and the effect of a correction of the spherical aberration on the circularity of the resulting internal microchannels. Moreover, we demonstrate the application of this writing technique by creating microfluidic testing structures inside of a transparent standard polymer.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 28; Number 4; Pages 5801; 2020
DOI: 10.1364/oe.384948

Polarization nano-tomography of tightly focused light landscapes by self-assembled monolayers

Author(s):

Eileen Otte, Kemal Tekce, Sebastian Lamping, Bart Jan Ravoo and Cornelia Denz
Abstract:

“Recently, four-dimensional (4D) functional nano-materials have attracted considerable attention due to their impact in cutting-edge fields such as nano-(opto)electronics, -biotechnology or -biomedicine. Prominent optical functionalizations, representing the fourth dimension, require precisely tailored light fields for its optimal implementation. These fields need to be like-wise 4D, i.e., nano-structured in three-dimensional (3D) space while polarization embeds additional longitudinal components. Though a couple of approaches to realize 4D fields have been suggested, their breakthrough is impeded by a lack of appropriate analysis techniques. Combining molecular self-assembly, i.e., nano-chemistry, and nano-optics, we propose a polarization nano-tomography of respective fields using the functional material itself as a sensor. Our method allows a single-shot identification of non-paraxial light fields at nano-scale resolution without any data post-processing. We prove its functionality numerically and experimentally, elucidating its amplitude, phase and 3D polarization sensitivity. We analyze non-paraxial field properties, demonstrating our method’s capability and potential for next generation 4D materials.”

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Publication: Nature Communications
Issue/Year: Nature Communications volume 10, Article number: 4308 (2019)
DOI: 10.1038/s41467-019-12127-3

Chain of optical vortices synthesized by a Gaussian beam and the double-phase-ramp converter

Author(s):

Anna Khoroshun, Oleksii Chernykh, Halyna Tatarchenko, Shunichi Sato, Yuichi Kozawa, Agnieszka Popiołek-Masajada, Mateusz Szatkowski, and Weronika Lamperskan

Abstract:

“A full theoretical and experimental analysis of the chain of phase singularities generated when a Gaussian beam passes a double-phase-ramp converter is presented. The overall output beam structure includes a system of interrelated optical vortices (OVs) whose trajectories form a three-dimensional singular skeleton that can be applied for the trapping and guiding of microparticles. The internal structure of each individual phase singularity is characterized by the OV topological charge and by the morphology parameters of equal intensity ellipses in the OV-core area: ellipticity (minor-to-major axes ratio) and the inclination angle. The morphology parameters’ evolution is shown to be valuable for the metrology applications.”

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Publication: OSA Continuum
Issue/Year: Vol. 2, Issue 2, pp. 320-331 (2019)
DOI: 10.1364/OSAC.2.000320

Measuring orbital angular momentums of light based on petal interference patterns

Author(s):

Shengzhe Pan and Chunying Pei and Shuang Liu and Jin Wei and Di Wu and Zhanou Liu and Yaling Yin and Yong Xia and Jianping Yin

Abstract:

“We demonstrate an interferometric method to measure the topological charges of the vortex beams carrying orbital angular momentums (OAMs). The petal interference patterns are generated by combining modulated vortex beams and an unmodulated incident Gaussian beam reflected by a spatial light modulator. The number of petals is in agreement with the value of OAM that the modulated beam carries, by which we analyze the characteristic of interference patterns of integer OAM beams, including intensity profiles, phase profiles, and hologram structures. We also uncover the principle of how radial parameter l influences the hollow radius of OAM beams. Beams carrying non-integer orbital angular momentums are visualized with our method, from which we observe the evolution of a speckle generated by the decimal part of holograms. A kind of hologram is designed to prove that the petal near the singularity line is separated owing to the diffraction enhancement. All the experiment results agree well with the simulated results.”

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Publication: OSA Continuum
Issue/Year: OSA Continuum Volume 1, Issue 2 (2018)
DOI: 10.1364/OSAC.1.000451

Laser surface structuring of diamond with ultrashort Bessel beams

Author(s):

Sanjeev Kumar, Shane M. Eaton, Monica Bollani, Belén Sotillo, Andrea Chiappini, Maurizio Ferrari, Roberta Ramponi, Paolo Di Trapani, Ottavia Jedrkiewicz

Abstract:

“We investigate the effect of ultrafast laser surface machining on a monocrystalline synthetic diamond sample by means of pulsed Bessel beams. We discuss the differences of the trench-like microstructures generated in various experimental conditions, by varying the beam cone angle, the energy and pulse duration, and we present a brief comparison of the results with those obtained with the same technique on a sapphire sample. In diamond, we obtain V-shaped trenches whose surface width varies with the cone angle, and which are featured by micrometer sized channels having depths in the range of 10–20 μm. By laser writing crossed trenches we are also able to create and tailor on the diamond surface pillar-like or tip-like microstructures potentially interesting for large surface functionalization, cells capturing and biosensing.”

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Publication: Scientific Reports
Issue/Year: Scientific Reports 8, Article number: 14021 (2018)
DOI: 10.1038/s41598-018-32415-0

Generation of elliptic perfect optical vortex and elliptic perfect vector beam by modulating the dynamic and geometric phase

Author(s):

Delin Li and Chenliang Chang and Shouping Nie and Shaotong Feng and Jun Ma and Caojin Yuan

Abstract:

“We propose a method for generating an elliptic perfect vector beam (EPVB) by modulating the dynamic and geometric phases. It is theoretically demonstrated that the shape of the beam can be changed from circle to ellipse by setting the scale factor m of the dynamic phase, but the diameter of it is independent on the topological charge and the polarization order. Since the geometric phases provided by the dialectic Q-plate vary with the polarization state of the illumination beam, EPVB can be converted to the elliptic perfect optical vortex (EPOV) beam by changing the polarization state of the illuminating beam. Therefore, we also provide an alternative method to generate the EPOV beam. The experimental results agree well with the theoretical expectations.”

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Publication: Applied Physics Letters
Issue/Year: Applied Physics Letters Volume 113, Issue 12
DOI: 10.1063/1.5048327

Nonlinear generation of Airy vortex beam

Author(s):
Hui Li and Haigang Liu and Xianfeng Chen

Abstract:

“Recently, hybrid beams have sparked considerable interest because of their properties coming from different kinds of beams at the same time. Here, we experimentally demonstrate Airy vortex beam generation in the nonlinear frequency conversion process when the fundamental wave with its phase modulated by a spatial light modulator is incident into a homogeneous nonlinear medium. In our experiments, second harmonic Airy circle vortex beams and Airy ellipse vortex beams were generated and the topological charge was also measured. The parabolic trajectory of those Airy vortex beams can be easily adjusted by altering the fundamental wave phase. This study provides a simple way to generate second harmonic Airy vortex beams, which may broaden its future use in optical manipulation and light-sheet microscopy.”

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Publication: Optics Express
Issue/Year: Optics Express Volume 26, Issue 16
DOI: 10.1364/oe.26.021204

Multiple-plane image formation by Walsh zone plates

Author(s):

Federico Machado, Vicente Ferrando, Fernando Giménez, Walter D. Furlan, and Juan A. Monsoriu

Abstract:

“A radial Walsh filter is a phase binary diffractive optical element characterized by a set of concentric rings that take the phase values 0 or π, corresponding to the values + 1 or −1 of a given radial Walsh function. Therefore, a Walsh filter can be re-interpreted as an aperiodic multifocal zone plate, capable to produce images of multiple planes simultaneously in a single output plane of an image forming system. In this paper, we experimentally demonstrate for the first time the focusing capabilities of these structures. Additionally, we report the first achievement of images of multiple-plane objects in a single image plane with these aperiodic diffractive lenses.”

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Publication: Optics Express
Issue/Year: Optics Express Volume 26, Issue 16
DOI: 10.1364/OE.26.021210

Shaping the on-axis intensity profile of generalized Bessel beams by iterative optimization methods

Author(s):

Runze Li and Xianghua Yu and Tong Peng and Yanlong Yang and Baoli Yao and Chunmin Zhang and Tong Ye
Abstract:

“The Bessel beam belongs to a typical class of non-diffractive optical fields that are characterized by their invariant transverse profiles with the beam propagation. The extended and uniformed intensity profile in the axial direction is of great interest in many applications. However, ideal Bessel beams only rigorously exist in theory; the Bessel beams generated in the experiment are always quasi-Bessel beams with finite focal extensions and varying intensity profiles along the propagation axis. The ability to shape the on-axis intensity profile to meet specific needs is essential for many applications. Here, we demonstrate an iterative optimization based approach to engineer the on-axis intensity of Bessel beams through design and fine-tune processes. Starting with a standard axicon phase mask, the design process uses the computed on-axis beam profile as a feedback in the iterative optimization process, which searches for the optimal radial phase distribution that can generate a so-called generalized Bessel beam with the desired on-axis intensity profile. The fine-tune process repeats the optimization processing by using the adjusted target on-axis profile according to the measured one. Our proposed method has been demonstrated in engineering several quasi-Bessel beams with customized on-axis profiles. The high accuracy and high energy throughput merit its use in many applications. This method is also suitable to engineer higher-order Bessel beams by adding appropriate vortex phases into the designed phase mask.”

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Publication: Journal of Optics
Issue/Year: Journal of Optics, Volume 20, Number 8 (2018)
DOI: 10.1088/2040-8986/aace46

Three-dimensional vectorial multifocal arrays created by pseudo-period encoding

Author(s):

Tingting Zeng and Chenliang Chang and Zhaozhong Chen and Hui-Tian Wang and Jianping Ding

Abstract:

“Multifocal arrays have been attracting considerable attention recently owing to their potential applications in parallel optical tweezers, parallel single-molecule orientation determination, parallel recording and multifocal multiphoton microscopy. However, the generation of vectorial multifocal arrays with a tailorable structure and polarization state remains a great challenge, and reports on multifocal arrays have hitherto been restricted either to scalar focal spots without polarization versatility or to regular arrays with fixed spacing. In this work, we propose a specific pseudo-period encoding technique to create three-dimensional (3D) vectorial multifocal arrays with the ability to manipulate the position, polarization state and intensity of each focal spot. We experimentally validated the flexibility of our approach in the generation of 3D vectorial multiple spots with polarization multiplicity and position tunability.”

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Publication: Journal of Optics
Issue/Year: Journal of Optics, Volume 20, Number 6
DOI: 10.1088/2040-8986/aac1de