PhD Defense of JANKOWSKI Andrzej

The transmission of analogue or digital signals at millimetre wavelengths plays a key role in many fields such as telecommunications, spectroscopy or radar. The generation of RF signals by optical means makes it possible to generate such signals in a wide range of frequency range. In this thesis, the heterodyne beat of two optical signals is used to excite a fast photodiode that is used as a photomixer. We were particularly interested in the possibility of combining several photodiodes in parallel to overcome the limitations of a single component and increase the power of the millimeter signal. Our photodiodes are of unipolar transport (Uni- Travelling-Carrier: UTC) type, they are integrated into an InP-based circuit that also includes guides passive optical waves, MMI couplers and power and microwave supply circuits. In our work, two approaches for the production of high output power in the wave domain millimetres are studied.
The first is based on the design and characterization of a new generation of Wilkinson power combiner in coplanar technology with 2 and 4 UTC photodiodes as sources. This solution targets the frequency range around 70 GHz. The total bandwidth at which the combiner of Wilkinson achieves optimal performance is about 6 GHz and 3 GHz for 2-way and 4-way topologies tracks, respectively. The second approach is based on UTC photodiode structures with integrated planar antenna. Dipole antenna and "butterfly node" antenna topologies are studied. Three-way structures photodiodes and dipole antenna targets the frequency range from 90 GHz to 110 GHz, but the results of simulation show that additional bands can be reached up to 300 GHz. For their part, the antenna structures with "bow tie" antennas show larger useful bandwidths. Thus, the width of the resulting band varies from 46 GHz for the three-photodiodes circuit to 126 GHz for a two-phase structure photodiode. All devices were manufactured in clean rooms on InP substrates and were experimentally characterized.