THz waves, typically between 0.1 THz and 10 THz, have great potential for a wide range of biomedical diagnostic applications, as well as for the fundamental study of a variety of biomolecules. Indeed, many biomolecules and biomolecular complexes exhibit relevant intramolecular and intermolecular resonances in this frequency range, paving the way for a wide range of biomedical and diagnostic applications. THz biosensing is therefore a fast-growing field of research. An extraordinary advantage of THz spectroscopy for biological applications is that it enables direct, label-free probing of the interaction of biomolecules with THz radiation. The aim of this internship is to develop original THz photonic crystal cavities offering a high THz electric field concentration with an ultra-high quality factor, and thus optimized for high-sensitivity THz biosensing. Òur group has recently realized THz cavities providing high electric field confinement with a quality factor of a few tens but limited by the use of metals with ohmic losses. To overcome these limitations, the candidate will realize dielectrically patterned, metal-free, THz photonic crystal cavities that will be further implemented into THz biosensors, to come closer to today's state-of-the-art bioanalytical tools. The candidate will design the photonic crystal cavities using simulations based on finite element method, participate to their fabrication and investigate their optical properties using THz spectroscopy systems.