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Free-form microoptics is a promising field showing immense potential in providing functional tools for light control, imaging and material processing. At the moment there is a huge drive in merging these objects to mesoscale – ensuring nano-/micro-features yet being mm-cm in overall size. One of the promising technologies to produce such elements is 3D laser lithography (3DLL). It has been shown to be a superb for fabrication of 3D objects with resolution and surface roughness control down to nm level with overall size to cm range [1]. For this reason it was employed to manufacture integrated 3D optical elements on functional substrates for spatial light control [2], imaging [3] and material processing [4].
Despite current progress there is some limitations concerning mesooptical element 3D printing. Common 3DLL systems uses galvo-scanners for beam deflection. While it can be very rapid (translation velocity in cm/s range), only objects that do not exceed working field of an objective can be printed continuously, which is ~100 µm for objectives having NA>1. Segment-by-segment fabrication have to be employed for bigger objects. At every edge where two segments meet, this induces defects called “stitches”. In optical element, it forces to sacrifice their quality [5] or use alternative manufacturing techniques [6].
In this work we present a stitch-free 3D printing of functional mesoscale lenses with an overall size up to several mm. These include mm sized refractive microlenses, cylindrical and Fresnel lenses. It was made possible by real-time synchronization linear stages and galvo-scanners for rapid (several mm/s translation velocity) continuous writing. Mesooptical elements were produced in a single technological step showing the simplicity and potency of 3DLL. Qualitative and quantitative characterization of mesooptical elements was performed, their optical resiliency (LIDT – Laser Induced Damage Threshold) was assesed. The experimental work proves the 3DLL as suitable technique for the fabrication of diverse mesooptical elements and their function to be practically applicable for light flow, imaging and material processing.
References
[1] L. Jonušauskas, S. Juodkazis, and M. Malinauskas, "Optical 3D Printing: Bridging the Gaps in the Mesoscale," J. Opt. 20(5), 053001 (2018).
[2] A. Žukauskas, V. Melissinaki, D. Kaškelytė, M. Farsari, and M. Malinauskas, "Improvement of the Fabrication Accuracy of Fiber Tip Microoptical Components via Mode Field Expansion," J. Laser Micro. Nanoeng. 9(1), 68-72 (2014).
[3] T. Gissibl, S. Thiele, A. Herkommer, H. Giessen, "Two-Photon Direct Laser Writing of Ultracompact Multi-Lens Objectives," Nat. Photonics 10(8), 554-560 (2016).
[4] E. E. Morales-Delgado, L. Urio, D. B. Conkey, N. Stasio, D. Psaltis, and C. Moser "Three-dimensional microfabrication through a multimode optical fiber," Opt. Express 25(6), 703-7045 (2017).
[5] H. Ni, G. Yuan, L. Sun, N. Chang, D. Zhang, R. Chen, L. Jiang, H. Chen, Z. Gu, and X. Zhao, "Large-Scale Sigh-Numerical-Aperture Super-Oscillatory Lens Fabricated by Direct Laser Writing Lithography", RSC Advances 8(36), 20117-20123 (2018).
[6] X. Chen, W. Liu, B. Dong, J. Lee, H. O. T. Ware. H. F. Zhang, and C. Sun, "High-Speed 3D Printing of Millimeter-Size Customized Aspheric Imaging Lenses with Sub 7 nm Surface Roughness," Adv. Mater. 30(18), 1705683 (2018).
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