Integrated Photonic-based Low Noise Radiometer for Millimeter and Sub-Millimeter Applications

Millimeter-wave and THz photonic radiometers based on electro-optic upconversion represent a novel detection approach to overcome the limitations in terms of volume, size and complexity of state-of-the-art detectors based on low noise amplifiers (LNAs) and mixers. Theoretical studies have shown that room-temperature radiometers based on an efficient upconverter followed by a direct detection stage could be competitive with conventional, and even cryogenic, mixers and LNAs in the THz range. In this work we present the development of a Lithium Niobate (LN) Photonic Integrated Circuit (PIC) as part of an integrated upconversion radiometer. Two optical components: an asymmetric Mach-Zehnder interferometer (AMZI) and a Whispering Gallery Mode Resonator (WGMR) were designed, fabricated and characterized. An Extinction Ratio (ER) of 25 dB and an intrinsic quality factor of 10
⁵
were achieved for the AMZI and the WGMR, respectively. Based on the characterization results of the first PIC, a second one was designed and fabricated, where the antenna for RF signal detection has been included. Details of the antenna design are also presented here.