HBV frequency multiplier 2D arrays and application

Abstract: The utilisation of the THz spectrum ( 0.3-3 THz ) is hampered by technological difficulties to generate power at these frequencies. Applications within diverse fields such as radio astronomy, security imaging, life sciences, high data rate communications and production monitoring could benefit significantly from compact, high power THz signal sources operating at room temperature. This thesis reports on the design and fabrication aspects of varactor diode based 2D array frequency multipliers. Both free space operating and waveguide en- closed Heterostructure Barrier Varactors (HBVs) arrays are discussed in detail. The goal of this work has been to design, fabricate and characterise high power varactor 2D array frequency multipliers, enabling increased power handling capabilities and output power of future THz frequency multipliers. This approach is expected to offer excellent frequency and power scalability for THz signal sources. An altogether waveguide integrated 249 GHz HBV 2D array frequency tripler is presented together with measurement data. With an output power of 18 mW at 248 GHz and a conversion efficiency of 2 %, this is the highest frequency of operation and output power reported to date for waveguide enclosed 2D array frequency multipliers. A 346 GHz imaging system is also presented as an application example for powerful THz signal sources. The system uses an imaging algorithm based on the Born approximation and produces images with a voxel size of 0.1 × 0.1 mm2 (approximately 1/10 of the free space wavelength).