Integrated Optics

Waveguide Simulations

Our Photonics group has accumulated significant know-how on the subject of waveguide simulations. It doesn't matter whether you are interested in the single- or multimode range we can provide suitable software tools for any application.

To model multimode waveguides we mainly use the non sequential mode by Zemax. It allows to simulate the propagation of rayse through any desired geometry and to detect them at any definable place. To get accurate results the investigated structures need to be at least 10 times the size of the wavelength. Therefore the ray tracing method is only suitable for multimode systems with diameters larger than 50 µm.

When modelling singlemode waveguides or fibers wave-optical phenomenons (like diffraction and interference) need to be taken into consideration. There is a BPM software package for guided wave optics called BeamPROP by Synopsys/RSoft. There are two methods available. The mode-solver allows do calculate the energy distribution along the waveguide's cross section. The beam propagation method on the other hand can model the field distribution across the desired component. BeamPROP can solve 2D as well as 3D problems.

Fabrication of Waveguides

 

In the case of fabricating waveguides we mainly rely on external partners. We maintain a close cooperation with companies like Variooptics AG in Heiden. vario-optics ag is specialised in the fabrication of polymer waveguide systems using direct writing techniques or mask exposure.

State of the art producible multimode waveguides have a cross section between 50 μm and 400 μm. Based on this technology an electro-optical circuit board has been developed in a cooperation project. These OECB technology can be used to implement datacom and sensor applications.

Characterization of Waveguides

Among the most important characteristics in integrated optics are transmission and loss measurements to determine the attenuation properties. For that usually the cut-back method is used where the attenuation of a waveguide is determined by measuring the transmission of varying lengths of waveguide pieces. Since the geometry and the side wall roughness of the waveguide's core have a strong influence on the losses the geometry has to be optimised (by simulation) and the roughness has to be determined (by white light interferometry).

The further characterization of waveguides include the measurement of the mode-field using a beam-view camera and divergence or numerical aperture of a waveguide. In the process of developing waveguides thin film analytics is a decisive factor. Values like film thickness and refractive index of the applied materials provide important information about the quality and properties of the produced waveguide layers.