@unpublished{13346,
  abstract     = {{This article discusses the additive manufacturing and post-processing of axicons, and their performance evaluation using attenuation and near-field-measurements based fundamental techniques. The axicons are manufactured using the materials cyclic olefin copolymer (TOPAS) and polymethyl methacrylate (PMMA), for their respective use in terahertz and near-infrared applications. An emphasis is placed on the dip-coating-based post-processing. Interval dipping and intermittent hardening lead to excellent surface finish and transparency in case of additively-manufactured near-infrared axicons. The dip-coated samples exhibit surface roughness of sub 10nm, and a uniformly distributed thin layer coating over the axicon surface. In addition to the improved surface finish and transparency, the coatings are also closely matched in refractive index to the axicon material. Such post-processed axicons pave the way for rapid-prototyping and production.}},
  author       = {{Shrotri, Abhijeet Narendra and Starsaja, Annamarija and Joshi, Suraj and Preu, Sascha  and Stübbe, Oliver}},
  booktitle    = {{Optica Open}},
  issn         = {{2334-2536 }},
  keywords     = {{additive manufacturing, stereolithography, dip-coating, post-processing}},
  pages        = {{5}},
  publisher    = {{Optica Publishing Group}},
  title        = {{{Multispectral characterization of additively manufactured and dip-coated axicons}}},
  doi          = {{https://doi.org/10.1364/opticaopen.31149016}},
  year         = {{2026}},
}

@unpublished{13363,
  abstract     = {{This article discusses the additive manufacturing and post-processing of axicons, and their performance evaluation using attenuation and near-field-measurements based fundamental techniques. The axicons are manufactured using the materials cyclic olefin copolymer (TOPAS) and polymethyl methacrylate (PMMA), for their respective use in terahertz and near-infrared applications. An emphasis is placed on the dip-coating-based post-processing. Interval dipping and intermittent hardening lead to excellent surface finish and transparency in case of additively-manufactured near-infrared axicons. The dip-coated samples exhibit surface roughness of sub 10 nm, and a uniformly distributed thin layer coating over the axicon surface. In addition to the improved surface finish and transparency, the coatings are also closely matched in refractive index to the axicon material. Such post-processed axicons pave the way for rapid-prototyping and production.}},
  author       = {{Shrotri, Abhijeet Narendra and Starsaja, Annamarija and Joshi, Suraj  and Preu, Sascha and Stübbe, Oliver}},
  booktitle    = {{Photonics: Open Access Journal}},
  issn         = {{2304-6732 }},
  keywords     = {{additive manufacturing, stereolithography, dip-coating, post-processing}},
  pages        = {{15}},
  publisher    = {{MDPI }},
  title        = {{{Multispectral Characterization of Additively Manufactured and Dip-Coated Axicons}}},
  doi          = {{https://doi.org/10.20944/preprints202602.0389.v1}},
  year         = {{2026}},
}

@misc{13495,
  abstract     = {{The use of additive manufacturing for rapid prototyping of near-infrared and terahertz components provides seamless and error-free production. This article discusses the additive manufacturing and post-processing of axicons and their performance evaluation using attenuation and near-field-measurements based fundamental techniques. The axicons are manufactured using the materials cyclic olefin copolymer (TOPAS) and polymethyl methacrylate (PMMA), for their respective use in terahertz and near-infrared applications. The optical and terahertz components manufactured using traditional 3D-printing processes, e.g., fused filament fabrication or stereolithography apparatus exhibit high surface roughness in the range of 15 ± 2.5 µm, resulting in undesired propagation and scattering in the near infrared wavelengths. This research work proposes an economical post-processing technique for additively manufactured terahertz and near-infrared axicons for applications in multispectral characterization, e.g., bio-sensing. The authors used an enhanced method of dip-coating, which involves interval dipping and intermittent hardening to achieve better surface finish. An emphasis is placed on interval dipping and intermittent hardening, which lead to excellent transparency in case of additively-manufactured near-infrared axicons. The dip-coated samples exhibit surface roughness below 10 nm. With the use of heated resin material as the coating layer, due to reduced viscosity, the resin material distributes uniformly over the surface of the 3D-printed terahertz and near-infrared axicons. The authors also observed that the DOF length deviation between unprocessed and enhanced dip-coated axicons remains within the measurement error estimation from analytical calculations. In addition to the improved surface finish and transparency, the coatings are also closely matched in refractive index to the axicon material. Such post-processed axicons pave the way for producing a wide array of systems in the fields of communication, imaging, and bio-sensing.}},
  author       = {{Shrotri, Abhijeet Narendra and Starsaja, Annamarija and Joshi, Suraj and Preu, Sascha and Stübbe, Oliver}},
  booktitle    = {{Photonics}},
  issn         = {{2304-6732}},
  keywords     = {{additive manufacturing, stereolithography, dip-coating, post-processing}},
  number       = {{3}},
  publisher    = {{MDPI AG}},
  title        = {{{Multispectral Characterization of Additively Manufactured and Dip-Coated Axicons}}},
  doi          = {{10.3390/photonics13030264}},
  volume       = {{13}},
  year         = {{2026}},
}

@misc{7670,
  abstract     = {{Additive manufacturing (AM) and rapid prototyping process (RPP) have revolutionized the production of 3D objects in the last few decades. RPP has considerably increased the rate of production and the possibility of manufacturing prototypes in the fields of electrical, optical, and mechanical engineering. The manufacturing of optical prototypes including spherical, aspheric, and special kinds of lenses and lens arrays has reformed the fabrication of optical components. In this paper, specifically designed lens array prototypes for application in visible light communication (VLC) are introduced. These lens array prototypes are manufactured using the stereolithography apparatus (SLA) process. These lens arrays are designed to achieve optimal transmission of the light beam for VLC systems. One of the prototypes from the lens arrays contains primarily four spherical lenses and one thicker convex lens and the other contains one fresnel lens as a substitute for thicker convex lens. These lens arrays are further post-processed to achieve the required transparency. These lens array prototypes are tested using laser and LEDs. The ON-OFF keying modulated light beam was transmitted through the lens array at the sender side and focused on the photo-receiver using another lens array at the receiver side which is 200 cm apart. After evaluating these lens prototypes, it can be concluded that with appropriate post-processing and high-resolution stereolithography based manufacturing, a low data rate VLC link can be formed.}},
  author       = {{Shrotri, Abhijeet Narendra and Beyer, Micha and Schneider, Daniel Johann and Stübbe, Oliver}},
  booktitle    = {{Laser 3D Manufacturing VIII}},
  editor       = {{Helvajian, Henry and Gu, Bo and Chen, Hongqiang}},
  isbn         = {{978-1-5106-4189-1}},
  issn         = {{1996-756X}},
  keywords     = {{Additive manufacturing, 3D printing, Stereolithography apparatus, Spherical lenses, Fresnel lenses, Visible light communication}},
  location     = {{San Francisco }},
  publisher    = {{Society of Photo-Optical Instrumentation Engineers}},
  title        = {{{Manufacturing of lens array prototypes containing spherical and fresnel lenses for visible light communications using stereolithography apparatus}}},
  doi          = {{10.1117/12.2586907}},
  volume       = {{11677}},
  year         = {{2021}},
}

@misc{7676,
  author       = {{Shrotri, Abhijeet Narendra and Beyer, Micha and Stübbe, Oliver}},
  booktitle    = {{3D Printed Optics and Additive Photonic Manufacturing II : 6-10 April 2020, online only, France }},
  editor       = {{von Freymann, Georg and Herkommer, Alois M. and Flury, Manuel}},
  isbn         = {{978-1-5106-3470-1}},
  issn         = {{1996-756X}},
  keywords     = {{Fresnel lenses, Stereolithography apparatus, 3D printing, Photo-polymerization}},
  location     = {{Strasbourg (online)}},
  publisher    = {{SPIE}},
  title        = {{{Manufacturing and analyzing of cost-efficient fresnel lenses using stereolithography}}},
  doi          = {{10.1117/12.2555367}},
  volume       = {{11349}},
  year         = {{2020}},
}

@misc{7679,
  author       = {{Shrotri, Abhijeet Narendra and Beyer, Micha and Stübbe, Oliver}},
  booktitle    = {{	 Production engineering and management : proceedings 9th international conference, October 03 and 04, 2019, Trieste, Italy}},
  editor       = {{Padoano, Elio and Villmer, Franz-Josef}},
  isbn         = {{978-3-946856-04-7}},
  keywords     = {{3D printing, stereolithography, optical lens, light forming structures, convex lenses, concave lenses, refraction of light, focal length}},
  location     = {{Trieste}},
  pages        = {{227--240}},
  publisher    = {{Technische Hochschule Ostwestfalen-Lippe}},
  title        = {{{Evaluation of stereolithograghy processes for the production of lens prototypes}}},
  volume       = {{2019, 01}},
  year         = {{2019}},
}