JCJC - Jeunes chercheuses & jeunes chercheurs

Guide d'Onde TéraHertz et Applications aux Composants – GOTHAC

Submission summary

The objective of this project is the realisation of a new generation of Terahertz (THz) waveguide and the fabrication of an elementary component, the resonator, in the prospect of improving the conception of more complex and integrated THz systems. THz refers to electromagnetic wave spectrum form 100 GHz to 10 THz lying between microwave and optical spectra. In this domain, research interest has been substantially increasing due to the wide prospects of applications in astrophysics, biology, medicine, communication and security fields. However, the expansion of the THz domain requires the extension of microwave and optical technologies to develop building block functions for more complex and integrated components working at THz frequencies. In particular, the lack of competitive THz waveguide is a strong limiting factor. In this context, the interest of this project is the conception of THz-fibres based on the Photonic Band-Gap (PBG) guidance mechanism. These guides are composed by an hollow core surrounded by a photonic crystal cladding. Since the core is filled with air, the material absorption issue is avoided. Moreover, even if the photonic crystal is made with absorbent materials, if the induced PBG effect is sufficiently strong, the resulting waveguide attenuation is several orders lower than the material attenuation. This phenomenon allows the use of materials that are too absorbent for wave guidance by total internal reflection mechanism. In a first time, we will use silica glass (that has an attenuation around 50 dB/m at 0.5 THz) to design and fabricate a prototype with an attenuation around or lower than 1 dB/m. The performances of the prototype will be analysed with the help of dedicated characterisation tools that will be set up. A time domain based bench will be used to characterised transmission properties of the fibre and to optimise its opto-geometrical parameters. Based on this study, further improvements might be investigated. In order to extend the transmission window of the fibre to higher THz frequencies, the insertion of metal inclusions in the photonic crystal will be studied. These inclusions might increase the PBG effect, and thus, compensate the dramatic increase of silica absorption at frequencies above 1 THz. Finally, the use of less rigid materials like polyethylene will open the possibility to fabricate flexible THz-fibre. In a second time, the fabricated THz-fibre will be used as a building block for the conception of advanced components. The transposition of elementary functions (filtering, routing, switching) from microwave or optical to THz domains will be studied. Moreover, the size of THz wavelength allows the use of fabrication processes issued from both domains. In this prospect, we will realise a resonator. The association of a resonator configuration from microwave studies with the Thz-fibre properties (low attenuation and strong field confinement in the core) may yield a significative increase of the Q factor. The realisation of this resonator would be a significant illustration of the rich potential of this project for the conception of more complex and integrated functions and it opens the door to the development of a new generation of components dedicated to THz frequencies.

Project coordination

Georges HUMBERT (Organisme de recherche)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.


Help of the ANR 145,124 euros
Beginning and duration of the scientific project: - 36 Months

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