---
_id: '6901'
abstract:
- lang: eng
  text: Freeform optics belong to the increasingly important elements in optical research
    and industry, which pose several challenges regarding design and highly precise
    manufacturing. First being used in cameras and for focusing, nowadays freeform
    optics are used in a broad range of applications, from lighting to LiDAR, from
    endoscopy to photovoltaics, and from astronomical instruments to quantum cryptography.
    Designing freeform optics can be based on different theories and methods. Fabrication
    is possible by mechanical methods, such as diamond turning or high-precision milling,
    often followed by different polishing techniques, as well as laser-based techniques,
    mainly applying different lithographic techniques. Here, we give an overview of
    recent design and optimization methods, production methods used during the last
    years, and applications of freeform optics, including the possibility to combine
    freeform optics with tunability for different applications. We describe the opportunities
    of new applications as well as common problems and give an outlook towards future
    directions of research and development.
article_number: '35'
article_type: review
author:
- first_name: Tomasz
  full_name: Blachowicz, Tomasz
  last_name: Blachowicz
- first_name: Guido
  full_name: Ehrmann, Guido
  last_name: Ehrmann
- first_name: Johannes
  full_name: Fiedler, Johannes
  last_name: Fiedler
- first_name: Reinhard
  full_name: Kaschuba, Reinhard
  last_name: Kaschuba
- first_name: Andrea
  full_name: Ehrmann, Andrea
  id: '223776'
  last_name: Ehrmann
  orcid: 0000-0003-0695-3905
  orcid_put_code_url: https://api.orcid.org/v2.0/0000-0003-0695-3905/work/214321986
citation:
  alphadin: '<span style="font-variant:small-caps;">Blachowicz, Tomasz</span> ; <span
    style="font-variant:small-caps;">Ehrmann, Guido</span> ; <span style="font-variant:small-caps;">Fiedler,
    Johannes</span> ; <span style="font-variant:small-caps;">Kaschuba, Reinhard</span>
    ; <span style="font-variant:small-caps;">Ehrmann, Andrea</span>: Freeform Micro-Optical
    Elements—Recent Production Techniques, Opportunities and Challenges. In: <i>Micro</i>
    Bd. 6, MDPI AG (2026), Nr. 2'
  ama: Blachowicz T, Ehrmann G, Fiedler J, Kaschuba R, Ehrmann A. Freeform Micro-Optical
    Elements—Recent Production Techniques, Opportunities and Challenges. <i>Micro</i>.
    2026;6(2). doi:<a href="https://doi.org/10.3390/micro6020035">10.3390/micro6020035</a>
  apa: Blachowicz, T., Ehrmann, G., Fiedler, J., Kaschuba, R., &#38; Ehrmann, A. (2026).
    Freeform Micro-Optical Elements—Recent Production Techniques, Opportunities and
    Challenges. <i>Micro</i>, <i>6</i>(2). <a href="https://doi.org/10.3390/micro6020035">https://doi.org/10.3390/micro6020035</a>
  bibtex: '@article{Blachowicz_Ehrmann_Fiedler_Kaschuba_Ehrmann_2026, title={Freeform
    Micro-Optical Elements—Recent Production Techniques, Opportunities and Challenges},
    volume={6}, DOI={<a href="https://doi.org/10.3390/micro6020035">10.3390/micro6020035</a>},
    number={235}, journal={Micro}, publisher={MDPI AG}, author={Blachowicz, Tomasz
    and Ehrmann, Guido and Fiedler, Johannes and Kaschuba, Reinhard and Ehrmann, Andrea},
    year={2026} }'
  chicago: Blachowicz, Tomasz, Guido Ehrmann, Johannes Fiedler, Reinhard Kaschuba,
    and Andrea Ehrmann. “Freeform Micro-Optical Elements—Recent Production Techniques,
    Opportunities and Challenges.” <i>Micro</i> 6, no. 2 (2026). <a href="https://doi.org/10.3390/micro6020035">https://doi.org/10.3390/micro6020035</a>.
  ieee: T. Blachowicz, G. Ehrmann, J. Fiedler, R. Kaschuba, and A. Ehrmann, “Freeform
    Micro-Optical Elements—Recent Production Techniques, Opportunities and Challenges,”
    <i>Micro</i>, vol. 6, no. 2, 2026.
  mla: Blachowicz, Tomasz, et al. “Freeform Micro-Optical Elements—Recent Production
    Techniques, Opportunities and Challenges.” <i>Micro</i>, vol. 6, no. 2, 35, MDPI
    AG, 2026, doi:<a href="https://doi.org/10.3390/micro6020035">10.3390/micro6020035</a>.
  short: T. Blachowicz, G. Ehrmann, J. Fiedler, R. Kaschuba, A. Ehrmann, Micro 6 (2026).
date_created: 2026-05-11T20:35:02Z
date_updated: 2026-05-12T05:18:08Z
doi: 10.3390/micro6020035
file:
- access_level: open_access
  content_type: application/pdf
  creator: aehrmann
  date_created: 2026-05-11T20:34:29Z
  date_updated: 2026-05-11T20:34:29Z
  file_id: '6902'
  file_name: _2026_Blachowicz_Micro6_35.pdf
  file_size: 6220358
  relation: main_file
  success: 1
file_date_updated: 2026-05-11T20:34:29Z
has_accepted_license: '1'
intvolume: '         6'
issue: '2'
keyword:
- photopolymerization
- tunable micro-optical freeform elements
- two-photon polymerization
- multiphoton lithography
- direct laser writing
- diamond turning
language:
- iso: eng
oa: '1'
project:
- _id: 0ec202b7-cd76-11ed-89f4-a9e1a6dbdaa7
  name: Institut für Technische Energie-Systeme
publication: Micro
publication_identifier:
  eissn:
  - 2673-8023
publication_status: published
publisher: MDPI AG
quality_controlled: '1'
status: public
title: Freeform Micro-Optical Elements—Recent Production Techniques, Opportunities
  and Challenges
tmp:
  image: /images/cc_by.png
  legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
  name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
  short: CC BY (4.0)
type: journal_article
urn: urn:nbn:de:hbz:bi10-69017
user_id: '220548'
volume: 6
year: '2026'
...
---
_id: '669'
article_number: '167294'
article_type: original
author:
- first_name: Devika
  full_name: Sudsom, Devika
  last_name: Sudsom
- first_name: Tomasz
  full_name: Blachowicz, Tomasz
  last_name: Blachowicz
- first_name: Lothar
  full_name: Hahn, Lothar
  last_name: Hahn
- first_name: Andrea
  full_name: Ehrmann, Andrea
  id: '223776'
  last_name: Ehrmann
  orcid: 0000-0003-0695-3905
  orcid_put_code_url: https://api.orcid.org/v2.0/0000-0003-0695-3905/work/161442000
citation:
  alphadin: '<span style="font-variant:small-caps;">Sudsom, Devika</span> ; <span
    style="font-variant:small-caps;">Blachowicz, Tomasz</span> ; <span style="font-variant:small-caps;">Hahn,
    Lothar</span> ; <span style="font-variant:small-caps;">Ehrmann, Andrea</span>:
    Vortex nucleation and propagation in magnetic double-wedges and semi-squares for
    reliable quaternary storage systems. In: <i>Journal of Magnetism and Magnetic
    Materials</i> Bd. 514, Elsevier (2020)'
  ama: Sudsom D, Blachowicz T, Hahn L, Ehrmann A. Vortex nucleation and propagation
    in magnetic double-wedges and semi-squares for reliable quaternary storage systems.
    <i>Journal of Magnetism and Magnetic Materials</i>. 2020;514. doi:<a href="https://doi.org/10.1016/j.jmmm.2020.167294">10.1016/j.jmmm.2020.167294</a>
  apa: Sudsom, D., Blachowicz, T., Hahn, L., &#38; Ehrmann, A. (2020). Vortex nucleation
    and propagation in magnetic double-wedges and semi-squares for reliable quaternary
    storage systems. <i>Journal of Magnetism and Magnetic Materials</i>, <i>514</i>.
    <a href="https://doi.org/10.1016/j.jmmm.2020.167294">https://doi.org/10.1016/j.jmmm.2020.167294</a>
  bibtex: '@article{Sudsom_Blachowicz_Hahn_Ehrmann_2020, title={Vortex nucleation
    and propagation in magnetic double-wedges and semi-squares for reliable quaternary
    storage systems}, volume={514}, DOI={<a href="https://doi.org/10.1016/j.jmmm.2020.167294">10.1016/j.jmmm.2020.167294</a>},
    number={167294}, journal={Journal of Magnetism and Magnetic Materials}, publisher={Elsevier},
    author={Sudsom, Devika and Blachowicz, Tomasz and Hahn, Lothar and Ehrmann, Andrea},
    year={2020} }'
  chicago: Sudsom, Devika, Tomasz Blachowicz, Lothar Hahn, and Andrea Ehrmann. “Vortex
    Nucleation and Propagation in Magnetic Double-Wedges and Semi-Squares for Reliable
    Quaternary Storage Systems.” <i>Journal of Magnetism and Magnetic Materials</i>
    514 (2020). <a href="https://doi.org/10.1016/j.jmmm.2020.167294">https://doi.org/10.1016/j.jmmm.2020.167294</a>.
  ieee: D. Sudsom, T. Blachowicz, L. Hahn, and A. Ehrmann, “Vortex nucleation and
    propagation in magnetic double-wedges and semi-squares for reliable quaternary
    storage systems,” <i>Journal of Magnetism and Magnetic Materials</i>, vol. 514,
    2020.
  mla: Sudsom, Devika, et al. “Vortex Nucleation and Propagation in Magnetic Double-Wedges
    and Semi-Squares for Reliable Quaternary Storage Systems.” <i>Journal of Magnetism
    and Magnetic Materials</i>, vol. 514, 167294, Elsevier, 2020, doi:<a href="https://doi.org/10.1016/j.jmmm.2020.167294">10.1016/j.jmmm.2020.167294</a>.
  short: D. Sudsom, T. Blachowicz, L. Hahn, A. Ehrmann, Journal of Magnetism and Magnetic
    Materials 514 (2020).
date_created: 2021-01-03T16:51:38Z
date_updated: 2026-03-17T15:29:33Z
department:
- _id: '103'
doi: 10.1016/j.jmmm.2020.167294
intvolume: '       514'
keyword:
- Magnetic nanostructures
- Wedges
- Micromagnetic simulation
- Vortex
- Magnetization reversal
- Iron
- Permalloy
- Lithography
language:
- iso: eng
publication: Journal of Magnetism and Magnetic Materials
publication_identifier:
  issn:
  - 0304-8853
publication_status: published
publisher: Elsevier
quality_controlled: '1'
status: public
title: Vortex nucleation and propagation in magnetic double-wedges and semi-squares
  for reliable quaternary storage systems
type: journal_article
user_id: '220548'
volume: 514
year: '2020'
...
---
_id: '635'
article_number: '5'
article_type: original
author:
- first_name: Devika
  full_name: Sudsom, Devika
  last_name: Sudsom
- first_name: Irén
  full_name: Juhász Junger, Irén
  last_name: Juhász Junger
- first_name: Christoph
  full_name: Döpke, Christoph
  last_name: Döpke
- first_name: Tomasz
  full_name: Blachowicz, Tomasz
  last_name: Blachowicz
- first_name: Lothar
  full_name: Hahn, Lothar
  last_name: Hahn
- first_name: Andrea
  full_name: Ehrmann, Andrea
  id: '223776'
  last_name: Ehrmann
  orcid: 0000-0003-0695-3905
  orcid_put_code_url: https://api.orcid.org/v2.0/0000-0003-0695-3905/work/161441923
citation:
  alphadin: '<span style="font-variant:small-caps;">Sudsom, Devika</span> ; <span
    style="font-variant:small-caps;">Juhász Junger, Irén</span> ; <span style="font-variant:small-caps;">Döpke,
    Christoph</span> ; <span style="font-variant:small-caps;">Blachowicz, Tomasz</span>
    ; <span style="font-variant:small-caps;">Hahn, Lothar</span> ; <span style="font-variant:small-caps;">Ehrmann,
    Andrea</span>: Micromagnetic Simulation of Vortex Development in Magnetic Bi-Material
    Bow-Tie Structures. In: <i>Condensed Matter</i> Bd. 5, MDPI (2020), Nr. 1'
  ama: Sudsom D, Juhász Junger I, Döpke C, Blachowicz T, Hahn L, Ehrmann A. Micromagnetic
    Simulation of Vortex Development in Magnetic Bi-Material Bow-Tie Structures. <i>Condensed
    Matter</i>. 2020;5(1). doi:<a href="https://doi.org/10.3390/condmat5010005">10.3390/condmat5010005</a>
  apa: Sudsom, D., Juhász Junger, I., Döpke, C., Blachowicz, T., Hahn, L., &#38; Ehrmann,
    A. (2020). Micromagnetic Simulation of Vortex Development in Magnetic Bi-Material
    Bow-Tie Structures. <i>Condensed Matter</i>, <i>5</i>(1). <a href="https://doi.org/10.3390/condmat5010005">https://doi.org/10.3390/condmat5010005</a>
  bibtex: '@article{Sudsom_Juhász Junger_Döpke_Blachowicz_Hahn_Ehrmann_2020, title={Micromagnetic
    Simulation of Vortex Development in Magnetic Bi-Material Bow-Tie Structures},
    volume={5}, DOI={<a href="https://doi.org/10.3390/condmat5010005">10.3390/condmat5010005</a>},
    number={15}, journal={Condensed Matter}, publisher={MDPI}, author={Sudsom, Devika
    and Juhász Junger, Irén and Döpke, Christoph and Blachowicz, Tomasz and Hahn,
    Lothar and Ehrmann, Andrea}, year={2020} }'
  chicago: Sudsom, Devika, Irén Juhász Junger, Christoph Döpke, Tomasz Blachowicz,
    Lothar Hahn, and Andrea Ehrmann. “Micromagnetic Simulation of Vortex Development
    in Magnetic Bi-Material Bow-Tie Structures.” <i>Condensed Matter</i> 5, no. 1
    (2020). <a href="https://doi.org/10.3390/condmat5010005">https://doi.org/10.3390/condmat5010005</a>.
  ieee: D. Sudsom, I. Juhász Junger, C. Döpke, T. Blachowicz, L. Hahn, and A. Ehrmann,
    “Micromagnetic Simulation of Vortex Development in Magnetic Bi-Material Bow-Tie
    Structures,” <i>Condensed Matter</i>, vol. 5, no. 1, 2020.
  mla: Sudsom, Devika, et al. “Micromagnetic Simulation of Vortex Development in Magnetic
    Bi-Material Bow-Tie Structures.” <i>Condensed Matter</i>, vol. 5, no. 1, 5, MDPI,
    2020, doi:<a href="https://doi.org/10.3390/condmat5010005">10.3390/condmat5010005</a>.
  short: D. Sudsom, I. Juhász Junger, C. Döpke, T. Blachowicz, L. Hahn, A. Ehrmann,
    Condensed Matter 5 (2020).
date_created: 2021-01-03T14:42:18Z
date_updated: 2026-03-17T15:29:29Z
department:
- _id: '103'
doi: 10.3390/condmat5010005
file:
- access_level: open_access
  content_type: application/pdf
  creator: aehrmann
  date_created: 2021-01-03T14:41:31Z
  date_updated: 2021-01-03T14:41:31Z
  file_id: '636'
  file_name: _2020_Sudsom_CondMatter5_5_corr.pdf
  file_size: 4886370
  relation: main_file
  success: 1
file_date_updated: 2021-01-03T14:41:31Z
funded_apc: '1'
has_accepted_license: '1'
intvolume: '         5'
issue: '1'
keyword:
- magnetic nanostructures
- micromagnetic simulation
- bow-tie structure
- vortex
- magnetization reversal
- iron
- permalloy
- lithography
language:
- iso: eng
oa: '1'
publication: Condensed Matter
publication_identifier:
  issn:
  - 2410-3896
publication_status: published
publisher: MDPI
quality_controlled: '1'
status: public
title: Micromagnetic Simulation of Vortex Development in Magnetic Bi-Material Bow-Tie
  Structures
type: journal_article
urn: urn:nbn:de:hbz:bi10-6351
user_id: '220548'
volume: 5
year: '2020'
...
---
_id: '582'
article_number: '165619 '
article_type: original
author:
- first_name: Tomasz
  full_name: Blachowicz, Tomasz
  last_name: Blachowicz
- first_name: Dorota
  full_name: Kosmalska, Dorota
  last_name: Kosmalska
- first_name: Christoph
  full_name: Döpke, Christoph
  last_name: Döpke
- first_name: Harald
  full_name: Leiste, Harald
  last_name: Leiste
- first_name: Lothar
  full_name: Hahn, Lothar
  last_name: Hahn
- first_name: Andrea
  full_name: Ehrmann, Andrea
  id: '223776'
  last_name: Ehrmann
  orcid: 0000-0003-0695-3905
  orcid_put_code_url: https://api.orcid.org/v2.0/0000-0003-0695-3905/work/166042188
citation:
  alphadin: '<span style="font-variant:small-caps;">Blachowicz, Tomasz</span> ; <span
    style="font-variant:small-caps;">Kosmalska, Dorota</span> ; <span style="font-variant:small-caps;">Döpke,
    Christoph</span> ; <span style="font-variant:small-caps;">Leiste, Harald</span>
    ; <span style="font-variant:small-caps;">Hahn, Lothar</span> ; <span style="font-variant:small-caps;">Ehrmann,
    Andrea</span>: Varying steps in hysteresis loops of Co square nano-frames. In:
    <i>Journal of Magnetism and Magnetic Materials</i> Bd. 491 (2019)'
  ama: Blachowicz T, Kosmalska D, Döpke C, Leiste H, Hahn L, Ehrmann A. Varying steps
    in hysteresis loops of Co square nano-frames. <i>Journal of Magnetism and Magnetic
    Materials</i>. 2019;491. doi:<a href="https://doi.org/10.1016/j.jmmm.2019.165619">10.1016/j.jmmm.2019.165619</a>
  apa: Blachowicz, T., Kosmalska, D., Döpke, C., Leiste, H., Hahn, L., &#38; Ehrmann,
    A. (2019). Varying steps in hysteresis loops of Co square nano-frames. <i>Journal
    of Magnetism and Magnetic Materials</i>, <i>491</i>. <a href="https://doi.org/10.1016/j.jmmm.2019.165619">https://doi.org/10.1016/j.jmmm.2019.165619</a>
  bibtex: '@article{Blachowicz_Kosmalska_Döpke_Leiste_Hahn_Ehrmann_2019, title={Varying
    steps in hysteresis loops of Co square nano-frames}, volume={491}, DOI={<a href="https://doi.org/10.1016/j.jmmm.2019.165619">10.1016/j.jmmm.2019.165619</a>},
    number={165619}, journal={Journal of Magnetism and Magnetic Materials}, author={Blachowicz,
    Tomasz and Kosmalska, Dorota and Döpke, Christoph and Leiste, Harald and Hahn,
    Lothar and Ehrmann, Andrea}, year={2019} }'
  chicago: Blachowicz, Tomasz, Dorota Kosmalska, Christoph Döpke, Harald Leiste, Lothar
    Hahn, and Andrea Ehrmann. “Varying Steps in Hysteresis Loops of Co Square Nano-Frames.”
    <i>Journal of Magnetism and Magnetic Materials</i> 491 (2019). <a href="https://doi.org/10.1016/j.jmmm.2019.165619">https://doi.org/10.1016/j.jmmm.2019.165619</a>.
  ieee: T. Blachowicz, D. Kosmalska, C. Döpke, H. Leiste, L. Hahn, and A. Ehrmann,
    “Varying steps in hysteresis loops of Co square nano-frames,” <i>Journal of Magnetism
    and Magnetic Materials</i>, vol. 491, 2019.
  mla: Blachowicz, Tomasz, et al. “Varying Steps in Hysteresis Loops of Co Square
    Nano-Frames.” <i>Journal of Magnetism and Magnetic Materials</i>, vol. 491, 165619,
    2019, doi:<a href="https://doi.org/10.1016/j.jmmm.2019.165619">10.1016/j.jmmm.2019.165619</a>.
  short: T. Blachowicz, D. Kosmalska, C. Döpke, H. Leiste, L. Hahn, A. Ehrmann, Journal
    of Magnetism and Magnetic Materials 491 (2019).
date_created: 2019-07-24T19:16:16Z
date_updated: 2026-03-17T15:29:22Z
department:
- _id: '103'
doi: 10.1016/j.jmmm.2019.165619
intvolume: '       491'
keyword:
- Magnetic nanostructures Magneto-optical Kerr effect (MOKE) Micromagnetic simulation
  Magnetization reversal Cobalt Lithography
language:
- iso: eng
publication: Journal of Magnetism and Magnetic Materials
publication_status: published
quality_controlled: '1'
status: public
title: Varying steps in hysteresis loops of Co square nano-frames
type: journal_article
user_id: '220548'
volume: 491
year: '2019'
...
---
_id: '340'
author:
- first_name: Andrea
  full_name: Ehrmann, Andrea
  id: '223776'
  last_name: Ehrmann
  orcid: 0000-0003-0695-3905
  orcid_put_code_url: https://api.orcid.org/v2.0/0000-0003-0695-3905/work/180914108
- first_name: Tomasz
  full_name: Blachowicz, Tomasz
  last_name: Blachowicz
citation:
  alphadin: '<span style="font-variant:small-caps;">Ehrmann, Andrea</span> ; <span
    style="font-variant:small-caps;">Blachowicz, Tomasz</span>: Interaction between
    magnetic nanoparticles in clusters. In: <i>AIMS Materials Science</i> Bd. 4 (2017),
    Nr. 2, S. 383–390'
  ama: Ehrmann A, Blachowicz T. Interaction between magnetic nanoparticles in clusters.
    <i>AIMS Materials Science</i>. 2017;4(2):383-390. doi:<a href="https://doi.org/10.3934/matersci.2017.2.383">10.3934/matersci.2017.2.383</a>
  apa: Ehrmann, A., &#38; Blachowicz, T. (2017). Interaction between magnetic nanoparticles
    in clusters. <i>AIMS Materials Science</i>, <i>4</i>(2), 383–390. <a href="https://doi.org/10.3934/matersci.2017.2.383">https://doi.org/10.3934/matersci.2017.2.383</a>
  bibtex: '@article{Ehrmann_Blachowicz_2017, title={Interaction between magnetic nanoparticles
    in clusters}, volume={4}, DOI={<a href="https://doi.org/10.3934/matersci.2017.2.383">10.3934/matersci.2017.2.383</a>},
    number={2}, journal={AIMS Materials Science}, author={Ehrmann, Andrea and Blachowicz,
    Tomasz}, year={2017}, pages={383–390} }'
  chicago: 'Ehrmann, Andrea, and Tomasz Blachowicz. “Interaction between Magnetic
    Nanoparticles in Clusters.” <i>AIMS Materials Science</i> 4, no. 2 (2017): 383–90.
    <a href="https://doi.org/10.3934/matersci.2017.2.383">https://doi.org/10.3934/matersci.2017.2.383</a>.'
  ieee: A. Ehrmann and T. Blachowicz, “Interaction between magnetic nanoparticles
    in clusters,” <i>AIMS Materials Science</i>, vol. 4, no. 2, pp. 383–390, 2017.
  mla: Ehrmann, Andrea, and Tomasz Blachowicz. “Interaction between Magnetic Nanoparticles
    in Clusters.” <i>AIMS Materials Science</i>, vol. 4, no. 2, 2017, pp. 383–90,
    doi:<a href="https://doi.org/10.3934/matersci.2017.2.383">10.3934/matersci.2017.2.383</a>.
  short: A. Ehrmann, T. Blachowicz, AIMS Materials Science 4 (2017) 383–390.
date_created: 2019-05-28T06:59:57Z
date_updated: 2026-03-17T15:28:44Z
doi: 10.3934/matersci.2017.2.383
intvolume: '         4'
issue: '2'
keyword:
- micromagnetic simulation
- magnetic nanoparticles
- nanoparticle cluster
- OOMMF
- stable intermediate state
- lithography
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://www.aimspress.com/article/10.3934/matersci.2017.2.383
oa: '1'
page: 383-390
publication: AIMS Materials Science
publication_identifier:
  eissn:
  - '2372-0484 '
status: public
title: Interaction between magnetic nanoparticles in clusters
type: journal_article
user_id: '33980'
volume: 4
year: '2017'
...