Photonic terahertz-wave generation, radiation and quasioptical integration

Abstract: This thesis deals with the uni-travelling-carrier photodiode (UTC-PD) based photonic generation of terahertz waves, antenna designs for the terahertz radiation and a novelcatadioptric lens for quasioptical integration.The ongoing and accomplished research work on the UTC-PD, its limitations and optimisation scopes for attaining higher bandwidth and higher output power have been discussed. An equivalent circuit of the UTC-PD is also proposed and has been fitted to S11 measurements up to 67 GHz.Several plausible quasioptical and non-quasioptical integration schemes for different UTC-PD application areas have also been discussed. Optimising for output powerrequires careful tradeoffs involving the epitaxial layer design, optical coupling, circuit design and antenna design. Considering the tradeoffs, several schemes for free-spaceTHz generation and waveguide integration techniques have been discussed.A novel catadioptric lens which is suitable for microwave and terahertz applications, for instance near-field imaging, has been presented. The focusing property of the lens hasbeen investigated using a 3D full-wave electromagnetic solver. Furthermore, the proposed catadioptric lens has been designed and fabricated from Delrin. Simulation andmeasurement results have been presented.

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