Integrated lithium niobate photonic millimetre-wave radar

Millimetre-wave (mmWave) radars are key enabler in the upcoming 6G era for high-resolution sensing and detection. Conventional photonic radars are mostly realized in tabletop systems composed of bulky discrete components, whereas the more compact integrated photonic radars are difficult to reach the mmWave bands owing to the unsatisfactory bandwidths and signal integrity of the underlying electro-optic modulators. Here we overcome these challenges and demonstrate a centimetre-resolution compact photonic mmWave radar based on a 4-inch wafer-scale thin-film lithium niobate (TFLN) technology. The TFLN photonic chip consists of a first electro-optic modulator for generating broadband radar waveforms via optical frequency multiplication, and a second modulator for de-chirping the received echoes. This greatly relieves the bandwidth requirements for the digital-to-analogue converter in the transmitter and analogue-to-digital converter in the receiver. Operating in the mmWave V band (40–50 GHz), we achieve multi-target ranging with a resolution of 1.50 cm and velocity measurement with a resolution of 0.067 m s⁻¹. Furthermore, we construct an inverse synthetic aperture radar with a two-dimensional resolution of 1.50 cm × 1.06 cm. Our integrated TFLN photonic mmWave radar chip provides a compact and cost-effective solution in the 6G era for high-resolution sensing and detection in vehicle radar, airborne radar and smart homes.