OFC is a waveguide

Institute for Microsystems Technology

SOI waveguides and components based on amorphous and polycrystalline silicon

Silicon photonics has developed significantly in recent years. Up to now, however, only isolated reports have been made about the implementation of amorphous SOI (silicon-on-insulator) waveguides with the aim of lowering the costs of optical systems and increasing flexibility in different optical applications. Compared to SOI, the use of amorphous or polycrystalline silicon for the production of optical waveguides and systems is not only more cost-effective, but also offers advantages because it can be combined with other substrate and waveguide materials.

For the production of such waveguides, hydrogenated amorphous silicon (a-Si: H) is made from monosilane (SiH4) deposited on oxidized silicon in order to produce integrated optical waveguides.

As these optical components can be integrated with the processes of microelectronics, there is also the prospect of being able to realize highly compact electronic and optical components on a common substrate. This considerably simplifies the use of optical connections in microelectronics, since all standard processes for manufacturing the integrated circuits are retained in terms of type and sequence and the optical connections are only added in the last step in the “back-end” process.

The content of the project is therefore the optimization of the deposition and structuring processes through the characterization of the material properties as well as the production of integrated optical waveguide structures such as couplers, Mach-Zehnder interferometers (Figure 1), tapers (Figure 2), modulators and resonators. In particular, nanoimprint lithography is to be used as a particularly cost-effective method for generating sub-micrometer structures.

Illustration 1: Mach-Zehnder interferometer (MZI) made of amorphous silicon                                 


Figure 2: 3D taper deposited over a-Si: H "photonic wire" waveguides


Timo Lipka


Funded by the German Research Foundation (DFG)


  • A. Harke, M. Krause, J. Müller, Low-loss singlemode amorphous silicon waveguides, Electronics Letters, vol. 41 no.25, 2005, pp. 1377-1379
  • A. Harke, T. Lipka, J. Amthor, O. Horn, M. Krause, J. Müller, Amorphous silicon 3D-tapers for Si photonic wires fabricated with shadow masks, IEEE PTL, vol. 20 no.17, 2008, pp. 1452-1454
  • T. Lipka, A. Harke, O. Horn, J. Amthor, J. Müller, Amorphous Waveguides for High Index Photonic Circuitry, OFC / NOEFC, 2009