Integrated 300 GHz Optoelectronic Mixer Based on Photonically-Pumped Low-Barrier Schottky Diodes

Photonic technologies bring intrinsic advantages in terahertz generation and detection, making them key enablers for a wide range of applications. However, currrent photonic-based terahertz receivers are limited in conversion loss compared to state-of-the-art electronic solutions. Here, we present the design, fabrication, and characterisation of an optoelectronic 220-330 GHz receiver, based on photonically-pumped Schottky barrier diodes (SBDs). The receiver integrates antiparallel low-barrier SBDs with a uni-travelling-carrier photodiode (UTC-PD) acting as the local oscillator (LO) signal generator. By combining these two components, the high-performance down-conversion provided by SBD-based mixers is paired with the photonic advantages in LO signal generation and distribution. A compact quasi-optical subharmonic receiver was fabricated and tested, achieving a minimum conversion loss of 18.1 dB. These results confirm the modelling process, since experimental results are in good agreement with simulations. Moreover, the receiver shows near-optimum performance for a pumping photocurrent as low as 5 mA, which proves the viability of the approach. While this work is an initial step with room for performance improvements, it highlights the potential of this solution to be used in applications like high-speed wireless communications, spectroscopy and imaging, and radio-astronomy.