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Li Z, Allegre O, Li L. Realising high aspect ratio 10 nm feature size in laser materials processing in air at 800 nm wavelength in the far-field by creating a high purity longitudinal light field at focus. LIGHT, SCIENCE & APPLICATIONS 2022; 11:339. [PMID: 36456549 PMCID: PMC9715648 DOI: 10.1038/s41377-022-00962-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 07/05/2022] [Accepted: 08/18/2022] [Indexed: 06/17/2023]
Abstract
In semiconductor and data storage device manufacturing, it is desirable to produce feature sizes less than 30 nm with a high depth-to-width aspect ratio on the target material rapidly at a low cost. However, optical diffraction limits the smallest focused laser beam diameter to around half of the laser wavelength (λ/2). The existing approach to achieving nanoscale fabrication is mainly based on costly extreme ultraviolet (EUV) technology operating within the diffraction limit. In this paper, a new method is shown to achieve materials processing resolution down to 10 nm (λ/80) at an infrared laser wavelength of around 800 nm in the far-field, in air, well beyond the optical diffraction limit. A high-quality longitudinal field with a purity of 94.7% is generated to realise this super-resolution. Both experiments and theoretical modelling have been carried out to verify and understand the findings. The ablation craters induced on polished silicon, copper, and sapphire are compared for different types of light fields. Holes of 10-30 nm in diameter are produced on sapphire with a depth-to-width aspect ratio of over 16 and a zero taper with a single pulse at 100-120 nJ pulse energy. Such high aspect ratio sub-50 nm holes produced with single pulse laser irradiation are rarely seen in laser processing, indicating a new material removal mechanism with the longitudinal field. The working distance (lens to target) is around 170 µm, thus the material processing is in the far field. Tapered nano-holes can also be produced by adjusting the lens to the target distance.
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Affiliation(s)
- Zhaoqing Li
- Department of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester, M13 9PL, UK
| | - Olivier Allegre
- Department of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester, M13 9PL, UK.
| | - Lin Li
- Department of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester, M13 9PL, UK.
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Cao Y, Hu LX, Hu YT, Zhao J, Zou DB, Yang XH, Zhang FP, Shao FQ, Yu TP. Direct acceleration of collimated monoenergetic sub-femtosecond electron bunches driven by a radially polarized laser pulse. OPTICS EXPRESS 2021; 29:30223-30236. [PMID: 34614749 DOI: 10.1364/oe.437827] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 08/19/2021] [Indexed: 06/13/2023]
Abstract
High-quality ultrashort electron beams have diverse applications in a variety of areas, such as 4D electron diffraction and microscopy, relativistic electron mirrors and ultrashort radiation sources. Direct laser acceleration (DLA) mechanism can produce electron beams with a large amount of charge (several to hundreds of nC), but the generated electron beams usually have large divergence and wide energy spread. Here, we propose a novel DLA scheme to generate high-quality ultrashort electron beams by irradiating a radially polarized laser pulse on a nanofiber. Since electrons are continuously squeezed transversely by the inward radial electric field force, the divergence angle gradually decreases as electrons transport stably with the laser pulse. The well-collimated electron bunches are effectively accelerated by the circularly-symmetric longitudinal electric field and the relative energy spread also gradually decreases. It is demonstrated by three-dimensional (3D) simulations that collimated monoenergetic electron bunches with 0.75° center divergence angle and 14% energy spread can be generated. An analytical model of electron acceleration is presented which interprets well by the 3D simulation results.
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Cardenas DE, Ostermayr TM, Di Lucchio L, Hofmann L, Kling MF, Gibbon P, Schreiber J, Veisz L. Sub-cycle dynamics in relativistic nanoplasma acceleration. Sci Rep 2019; 9:7321. [PMID: 31086214 PMCID: PMC6513988 DOI: 10.1038/s41598-019-43635-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 04/28/2019] [Indexed: 11/26/2022] Open
Abstract
The interaction of light with nanometer-sized solids provides the means of focusing optical radiation to sub-wavelength spatial scales with associated electric field enhancements offering new opportunities for multifaceted applications. We utilize collective effects in nanoplasmas with sub-two-cycle light pulses of extreme intensity to extend the waveform-dependent electron acceleration regime into the relativistic realm, by using 106 times higher intensity than previous works to date. Through irradiation of nanometric tungsten needles, we obtain multi-MeV energy electron bunches, whose energy and direction can be steered by the combined effect of the induced near-field and the laser field. We identified a two-step mechanism for the electron acceleration: (i) ejection within a sub-half-optical-cycle into the near-field from the target at >TVm-1 acceleration fields, and (ii) subsequent acceleration in vacuum by the intense laser field. Our observations raise the prospect of isolating and controlling relativistic attosecond electron bunches, and pave the way for next generation electron and photon sources.
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Affiliation(s)
- D E Cardenas
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, 85748, Garching, Germany
- Ludwig-Maximilian-Universität München, Am Couloumbwall 1, 85748, Garching, Germany
| | - T M Ostermayr
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, 85748, Garching, Germany
- Ludwig-Maximilian-Universität München, Am Couloumbwall 1, 85748, Garching, Germany
| | - L Di Lucchio
- Forschungszentrum Jülich GmbH, Institute for Advanced Simulation, Jülich Supercomputing Centre, D-52425, Jülich, Germany
| | - L Hofmann
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, 85748, Garching, Germany
- Ludwig-Maximilian-Universität München, Am Couloumbwall 1, 85748, Garching, Germany
| | - M F Kling
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, 85748, Garching, Germany
- Ludwig-Maximilian-Universität München, Am Couloumbwall 1, 85748, Garching, Germany
| | - P Gibbon
- Forschungszentrum Jülich GmbH, Institute for Advanced Simulation, Jülich Supercomputing Centre, D-52425, Jülich, Germany
- Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, 3001, Heverlee, Belgium
| | - J Schreiber
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, 85748, Garching, Germany
- Ludwig-Maximilian-Universität München, Am Couloumbwall 1, 85748, Garching, Germany
| | - L Veisz
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann Strasse 1, 85748, Garching, Germany.
- Department of Physics, Umeå University, SE-901 87, Umeå, Sweden.
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Marceau V, Varin C, Brabec T, Piché M. Femtosecond 240-keV electron pulses from direct laser acceleration in a low-density gas. PHYSICAL REVIEW LETTERS 2013; 111:224801. [PMID: 24329450 DOI: 10.1103/physrevlett.111.224801] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Indexed: 06/03/2023]
Abstract
We propose a simple laser-driven electron acceleration scheme based on tightly focused radially polarized laser pulses for the production of femtosecond electron bunches with energies in the few-hundreds-of-keV range. In this method, the electrons are accelerated forward in the focal volume by the longitudinal electric field component of the laser pulse. Three-dimensional test-particle and particle-in-cell simulations reveal the feasibility of generating well-collimated electron bunches with an energy spread of 5% and a temporal duration of the order of 1 fs. These results offer a route towards unprecedented time resolution in ultrafast electron diffraction experiments.
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Affiliation(s)
- Vincent Marceau
- Centre d'Optique, Photonique et Laser, Université Laval, Québec, Québec G1V 0A6, Canada
| | - Charles Varin
- Center for Research in Photonics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Thomas Brabec
- Center for Research in Photonics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Michel Piché
- Centre d'Optique, Photonique et Laser, Université Laval, Québec, Québec G1V 0A6, Canada
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Marceau V, Varin C, Piché M. Validity of the paraxial approximation for electron acceleration with radially polarized laser beams. OPTICS LETTERS 2013; 38:821-823. [PMID: 23503227 DOI: 10.1364/ol.38.000821] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
In the study of laser-driven electron acceleration, it has become customary to work within the framework of paraxial wave optics. Using an exact solution to the Helmholtz equation as well as its paraxial counterpart, we perform numerical simulations of electron acceleration with a high-power TM(01) beam. For beam waist sizes at which the paraxial approximation was previously recognized valid, we highlight significant differences in the angular divergence and energy distribution of the electron bunches produced by the exact and the paraxial solutions. Our results demonstrate that extra care has to be taken when working under the paraxial approximation in the context of electron acceleration with radially polarized laser beams.
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Affiliation(s)
- Vincent Marceau
- Centre d'Optique, Photonique et Laser, Université Laval, Québec, Canada.
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Direct Electron Acceleration with Radially Polarized Laser Beams. APPLIED SCIENCES-BASEL 2013. [DOI: 10.3390/app3010070] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Marceau V, April A, Piché M. Electron acceleration driven by ultrashort and nonparaxial radially polarized laser pulses. OPTICS LETTERS 2012; 37:2442-2444. [PMID: 22743415 DOI: 10.1364/ol.37.002442] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Exact closed-form solutions to Maxwell's equations are used to investigate the acceleration of electrons in vacuum driven by ultrashort and nonparaxial radially polarized laser pulses. We show that the threshold power above which significant acceleration takes place is greatly reduced by using a tighter focus. Moreover, electrons accelerated by tightly focused single-cycle laser pulses may reach around 80% of the theoretical energy gain limit, about twice the value previously reported with few-cycle paraxial pulses. Our results demonstrate that the direct acceleration of electrons in vacuum is well within reach of current laser technology.
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Affiliation(s)
- Vincent Marceau
- Centre d’Optique, Photonique et Laser, Université Laval 2375 Rue de la Terrasse, Québec, Québec G1V0A6, Canada.
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