Optical Waveguides and optical Mems

Over the last 30 years, a number of projects in integrated optics and optical MEMS has been performed by the PI at Universität Dortmund (1990 – 2003) and TU Ilmenau (2006 – 2017).

The following overview shows a selection of projects using integrated optics.

Optical MEMS will be added soon.


SiON waveguides with high core index but perfect match to singlemode fibres at 1300 / 1550 nm wavelength

Principle (left) and photograph (right) of a high-index waveguide with large evanescent field and almost circular field distribution

Transmission characteristics of an un-annealed PECVD SiON waveguide including coupling loss to singlemode fibres at both ends

M. Hoffmann, H. Bezzaoui, E. Voges:
Micromechanical Cantilever Resonators with integrated optical interrogation
In: Sensors and Actuators A44, (1994), 71-75
DOI: 10.1016/0924-4247(94)00776-4

M. Hoffmann, P. Kopka, E. Voges:
Low-loss fiber-matched low-temperature PECVD waveguides with small core dimensions for optical communication systems
In: IEEE Photonics Technology Letters 9 (1997), 1238-1240
DOI: 10.1109/68.618490


Integrated-optical 2x2 switches based on thermooptic switching in an adiabatic waveguide crossing (“thermooptical digital switch”) (partially funded within the EU-FP4 – ACTS project COBNET – Corporate Optical Backbone Networks)

Principle of an adiabatic waveguide switch with thermooptic switching realized in SiON technology

All figures:
© Martin Hoffmann (Lehrstuhl für Hochfrequenztechnik, Universität Dortmund), Dissertationsschrift

M. Hoffmann, P. Kopka, E. Voges:
Thermo-optical digital switch arrays in silica-on-silicon with defined zero-voltage state
In: IEEE Journal of Lightwave Technology 16 (1998), 395-400
DOI: 10.1109/50.661366

An integrated optical interferometer for laser tracking

(BMBF-funded project OPTIMI – Kompetenzdreieck Optische Mikrosysteme)

(Figures from BMBF-Abschlussbericht Kompetenzdreieck Optische Mikrosysteme, TU Ilmenau, 2014; Micromechanical Systems Group, Martin Hoffmann)

Optical interferometer based on silica-on-silicon waveguides and thermo-optical phase trimming combined with two sensor chips with integrated photodiodes (photodiodes integrated by CiS GmbH, Erfurt)

Principle view of a laser tracker system (single system; at least 3 systems needed for 3D trilateration of a moving tool center point (TCP)

Assembled interferometer device with fibre coupling / sensor chip, interferometer and GRIN-lens in relation to a ball pen

M. Hoffmann, S. Dickhut, E.Voges:
Fiber Ribbon Alignment Structures Based on Rhombus-Shaped Channels in Silicon
In: IEEE Photonics Technology Letters, 12 (2000), 828-830
DOI: 10.1109/68.853514

Markweg, Eric; Hoffmann, Martin; Schädel, Martin; Ortlepp, Hans-Georg; Brodersen, Olaf:
A combined fibre coupling/readout diode chip for use in integrated optical interferometry
In: Tagungsband Smart Systems Integration 2014, Wien, Austria, (USB stick, ISBN 978-3-86359-201-1)

Markweg, Eric ; Schädel, Martin; Brodersen, Olaf; Ortlepp, Hans Georg; Hoffmann, Martin; Mollenhauer, Olaf:
Mikrotechnische Umsetzung eines integriert optischen Michelson-Interferometers für Auflösungen im Sub-Nanometerbereich
In: Mikro-Nano-Integration: Beiträge des 5. GMM-Workshops, 8. - 9. Oktober 2014 in Ilmenau. - Berlin: VDE-Verl. - 2014, pp. 107-111 ISBN 978-3-8007-3632-4

Optical lens with refractive index gradient in the y-axis and spherical bending in x-axis for optimised planar integration of a 2D refractive index lens. top: design and stepwise realisisation of the index gradient; bottom: etched cylindrical lenses; index gradient slightly visible in SEM photo

Integrated planar interferometer in a bulk silica plate: Integration by deep silica etching

Principle of the planar interferometer and SEM photo of realized systems (etch depth in silica: 100 um, sidewall roughness (Ra) < 10 nm, angle of sidewall 89 °)

Weigel, Christoph; Markweg, Eric; Hoffmann, Martin:
Monolithisch in Kieselglas integriertes Interferometer
In: Proceedings MikroSystemTechnik Kongress 2015, 26.-28. Oktober 2015, Karlsruhe: VDE Verlag (2015) ISBN: 978-3-8007-4100-7

Weigel, Christoph; Markweg, Eric; Müller, Lutz; Schulze, Marcel; Gargouri, Hassan; Hoffmann, Martin:
A monolithic micro-optical interferometer deep etched into fused silica
In: Microelectronic Engineering, Volume 174 (2017), 25. April 2017, pp. 40-45
DOI: 10.1016/j.mee.2017.01.002

Integrated-optical switches based on “Electrowetting”

(funded by EU within the 7th framework program project SWIFT - Non-volatile optical Switch combining Integrated Photonics and Fluidics Technologies)

Micromechanical Systems Group, TU Ilmenau, Martin Hoffmann: system integration of electrostatic fluid actuation on optical chips (Si and SiN waveguides) from IMEC, Belgium)

(Further results to be published)

Günther, Sarah; Gropp, Sebastian; Hoffmann, Martin; D’heer, Herbert; van Thourhout, Dries; Neft, Anna; Bartels, Frank; Gradkowski, Kamil; Carroll, Lee; O’Brien, Peter; Lerma-arce, Cristina; Watté , Jan:
Electrowetting Controlled Non-Volatile Integrated Optical Switch
In: 44th European Conference on Optical Communication 2018, Rom, 23.-27. September 2018
DOI: 10.1109/ecoc.2018.8535585
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