Photonic-Assisted Microwave Harmonic Down-Conversion Based on Four-Wave Mixing in a Silicon Integrated Waveguide Doped With Reverse-Biased P-i-N Junction

We propose and demonstrate a highly efficient photonic-assisted microwave signal harmonic frequency down- conversion using four-wave mixing (FWM) in a silicon waveguide with a reverse-biased P-i-N junction. The FWM phenomenon occurred in the integrated waveguide due to the doped regions of the junction can increase the efficiency of free carrier removal from the waveguide region. Correspondingly, the conversion efficiency is up to 12.8 dB with the bias voltage of 30 V. The silicon waveguide is fully packaged with a grating coupling fiber array and a wire-bonded printed circuit board (PCB). By simply adjusting the low-frequency electrical LO, the down converter based on FWM can realize accurate tunable and ultra-wide frequency operation. This scheme can significantly reduce the high-frequency demand for LO source. In the experiment, the RF signals ranging from 8 GHz to 31 GHz are all down converted within 2 GHz by utilizing the 5.88.2 GHz LO signals, and signal-to-noise ratios (SNRs) larger than 50 dB are achieved. Moreover, the phase noise of the intermediate frequency (IF) signal is as low as -80.12 dBc/Hz at an offset frequency of 10 kHz and spurious free dynamic range (SFDR) is 105.5 dB center dot Hz(2/3) with 3rd-order FWM effect for the LO signal and 103.8 dB center dot Hz(2/3) with 4th-order FWM effect for the LO signal. This shows that the down conversion signal is reliable to further use in modern electrical systems such as microwave photonic radar.