Liquid Crystal Waveguide

Liquid crystal waveguides

© Fraunhofer IPMS
Simulation of light propagation in a waveguide with an LC-EOIW with increasing electric field strength (left). 1×2 LC-EOIW switch chip on a printed circuit board: bonded silicon wafers enclosing an LC layer. (center of image) Processed silicon wafer with Vernier-type LC microresonator filter (right).

Fraunhofer IPMS has developed a novel concept for electro-optically induced waveguides that features a liquid crystal core layer on a programmable electrode backplane configuration (LC-EOIW, Fig. 1 - left). This concept can be used to create new types of configurable devices.

Specifically, LC waveguides with low loss (propagation loss < 1 dB/cm) and sub-µs response time can be designed by using selected liquid crystals with large EO Kerr coefficients and high transmittance over a wide wavelength range (400 - 1600 nm) as core material. Such waveguides can be configured by electrically addressing specific electrodes to perform various optical functions (Fig. 1 - center), such as: n x m switching, variable optical power splitting, variable attenuation, modulation, or phase shifting. The technology can therefore be used in various applications that require configurability. For example, custom device designs have been developed to date for applications in optical telecommunications, fiber optic sensor networks, spectroscopy and information security.

Polarization-independent LC-EOIWs with very low polarization-dependent loss (PDL) over a wide attenuation range have also been developed. In this case, by using a special electrode arrangement in the waveguide design. Thereby, in this type of low PDL waveguide, both TE and TM polarized light waves propagate simultaneously within the waveguide, with an equal but variable transmission power. Similarly, Fraunhofer IPMS has developed LC core microring resonators (Fig. 1 - right) that can be used as tunable filters and add-drop multiplexers. The LC waveguide components are fabricated on 200-mm silicon wafers in the Fraunhofer IPMS clean room. These can be integrated with other components and their design can be adapted to the desired application.

Our services include design, fabrication and characterization of the devices as stand-alone devices or in combination with passive waveguides.