The first waveguide coupled phosphide-based UTC photodiodes grown by Solid Source Molecular Beam Epitaxy (SSMBE) are reported in this paper. Metal Organic Vapour Phase Epitaxy (MOVPE) and Gas Source MBE (GSMBE) have long been the predominant growth techniques for the production of high quality InGaAsP materials. The use of SSMBE overcomes the major issue associated with the unintentional diffusion of zinc in MOVPE and gives the benefit of the superior control provided by MBE growth techniques without the costs and the risks of handling toxic gases of GSMBE. The UTC epitaxial structure contains a 300 nm n-InP collection layer and a 300 nm n ++ -InGaAsP waveguide layer. UTC-PDs integrated with Coplanar Waveguides (CPW) exhibit 3 dB bandwidth greater than 65 GHz and output RF power of 1.1 dBm at 100 GHz. We also demonstrate accurate prediction of the absolute level of power radiated by our antenna integrated UTCs, between 200 GHz and 260 GHz, using 3d full-wave modelling and taking the UTC-to-antenna impedance match into account. Further, we present the first optical 3d full-wave modelling of waveguide UTCs, which provides a detailed insight into the coupling between a lensed optical fibre and the UTC chip.

Terahertz generation using high-speed photodiodes has found commercial application in many areas ranging across spectroscopy, imaging and communications. In this paper we discuss the optimization of high-speed photodiodes in terms of bandwidth and output power. We identify some of the main limitations in the generation of high output power in the Terahertz frequency band. We present a modelling tool for the numerical evaluation of antenna coupled uni-travelling carrier photodiodes and experimental evaluation of the fabricated designs. We also present a thermal analysis of the photodiodes alongside pulsed measurements of the output power saturation.

We report the first 60 GHz wireless link implementing a uni-traveling carrier photodiode (UTC-PD) at the transmitter and a photonic integrated chip incorporating a UTC-PD at the receiver. In this demonstration, a 64.5 GHz signal carrying 1 Gbps on-off keying (OOK) data was generated by heterodyning two optical tones into the transmitter UTC-PD. The signal was transmitted using a 24 dBi gain parabolic antenna over a wireless distance of three metres before reaching an identical receiver antenna. At the receiver, an electronic mixer was used to down-convert the received signal into an intermediate frequency of 12.5 GHz. The local oscillator to the electronic mixer was provided by heterodyne mixing of two optical tones generated using a UTC-PD that is monolithically integrated with semiconductor lasers. The down-converted signal was acquired by a real-time oscilloscope for offline processing, which showed zero error bits in a 10 5 bit-long transmission.

This study reports the experimental demonstration of a free space frequency domain self-heterodyne spectrometer utilising a high-speed Uni-Travelling Carrier photodiode (UTC-PD) as a coherent receiver. The transmission signal through the glucose solution was measured in the V-band (50-75 GHz) frequency range with a frequency resolution step of 40 MHz. Variations in glucose concentrations of as small as 1% weight were resolved.

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