Fig. 1. (Color online) Schematic diagram of the broadband RF channelizer based on an integrated optical comb source. Amp: erbium-doped fibre amplifier. OBPF: optical bandpass filter. PC: polarization controller. MRR: micro-ring resonator. OC: optical coupler. PM: phase modulator. Temp. Con.: temperature controller. DEMUX: de-multiplexer. Rx: Receiver. OSA: optical spectrum analyzer. (a) Channelizer based on 200 GHz microcomb MRR with 49 GHz passive MRR. (b) Schematic diagram of the broadband RF channelizer based on a soliton crystal microcomb. EDFA: erbium-doped fibre amplifier. PC: polarization controller. MRR: micro-ring resonator. WS: WaveShaper. PM: phase modulator. TEC: temperature controller. DEMUX: de-multiplexer. Rx: Receiver.

Fig. 2. (Color online) Schematic illustration of the (a) 200 GHz-FSR MRR and (b) 49 GHz-FSR MRR. (c) SEM image of the cross-section of the 200 GHz MRR before depositing the silica upper cladding.

Fig. 3. (Color online) Optical spectrum for the 200 GHz FSR micro-comb device. (a) The primary comb. (b) The secondary comb. (c) The Kerr comb with 300 nm span. (d) The shaped optical comb for the channelizer with less than 0.5 dB unflatness. (e) 20 and (f) seleted 4 comb lines modulated by RF signals.

Fig. 4. (Color online) Drop-port transmission spectrum of the passive on-chip 49 GHz MRR (a) with a span of 5 nm, (b) showing an FSR of 49 GHz, and (c) a resonance at 193.294 THz with full width at half maximum (FWHM) of 124.94 MHz, corresponding to a Q factor of 1.549 × 10⁶.

Fig. 5. (Color online) (a) The measured optical spectrum of the 200 GHz micro-comb and transmission of the 49 GHz MRR. Zoom-in views of the channels with different channelized RF frequencies. (b) Extracted channelized RF frequencies, the inset shows the corresponding optical frequencies of the comb lines and the spectral slicing resonances.

Fig. 6. RF response of the 200 GHz Channelizer. Measured optical spectrum of the 49 GHz MRR’s output with different input RF frequencies, with the temperature of the 49 GHz MRR set to (a) 24.0, (b) 24.5, (c) 25.0, and (d) 25.5 °C. (e) Channelized RF frequencies at different wavelength channels with different temperatures.

Fig. 7. (Color online) Channelized RF frequencies at different channels.

Fig. 8. (Color online) Extracted extinction ratio of channelized RF signals.

Fig. 9. (Color online) Optical spectrum of the generated soliton crystal microcomb with (a) 100 and (b) 40 nm span. (c) Flattened 92 comb lines.

Fig. 10. (Color online) (a) The measured optical spectrum of the micro-comb and drop-port transmission of passive MRRs. (b) Extracted channelized RF frequencies of the 92 channels, calculated from the spacing between the comb lines and the passive resonances. Note that the labelled channelized RF frequencies in (a) are adopted from accurate RF domain measurements using the Vector Network Analyzer, as shown in the next figure.

Fig. 11. (Color online) Measured RF transmission spectra of (a) the 92 channels and (b) zoom-in view of the first 4 channels. (b) Extracted channelized RF frequency and resolution. (d) Measured RF transmission spectra at different chip temperatures of the passive MRR.