Multi-functional microwave photonic circuit based on thin film lithium niobate platform

A multi-functional microwave photonic circuit with meshed architecture is designed and demonstrated on thin film lithium niobate platform. Taking the advantages of the fast response of the Pockels effect and optimized device design, the operation bandwidth of the chip exceeds 60GHz. By controlling the transmission paths of the photon at each node, the on-chip device resources are configurated as a variety of microwave links, corresponding to different signal processing functions. The capabilities of signal generation, down-conversion mixing with high dynamic range and self-interference cancellation with high suppression ratio are experimentally demonstrated. For signal generation, the chip can be regarded as a frequency doubler, and both linear and nonlinear frequency modulated waveforms are obtained with a time-bandwidth product of 2×10⁵ and an in-band spurious suppression ratio higher than 40dB. When configurated as a mixer, the chip achieves a spurious free dynamic range of 105 dB/Hz2/3 and a down-conversion efficiency of -7.4dB. The lithium niobate avoids the nonlinear carrier transportation and absorption existing in traditional silicon photonics, breaking the limitation of linearity and efficiency. As self-interference cancellation mode is set, the interference is suppressed by 50dB over 1.1GHz span. The uniformity of microfabrication in combination with the precise adjustment of the amplitude and phase of the optical field guarantees the high cancellation ratio. To the best of our knowledge, this photonic chip possesses the largest bandwidth and excellent comprehensive performance in terms of active signal processing among integrated multifunctional microwave photonic circuits.