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Abstract The generation of ultra-low-noise microwave and mmWave in miniaturized, chip-based platforms can transform communication, radar and sensing systems^1–3. Optical frequency division that leverages optical references and optical frequency combs has emerged as a powerful technique to generate microwaves with superior spectral purity than any other approaches^4–7. Here we demonstrate a miniaturized optical frequency division system that can potentially transfer the approach to a complementary metal-oxide-semiconductor-compatible integrated photonic platform. Phase stability is provided by a large mode volume, planar-waveguide-based optical reference coil cavity^8,9and is divided down from optical to mmWave frequency by using soliton microcombs generated in a waveguide-coupled microresonator^10–12. Besides achieving record-low phase noise for integrated photonic mmWave oscillators, these devices can be heterogeneously integrated with semiconductor lasers, amplifiers and photodiodes, holding the potential of large-volume, low-cost manufacturing for fundamental and mass-market applications¹³. 

We present a photonically driven on-chip millimeter wave (mmWave) source enabled by the heterogeneous integration of a high-speed InGaAs/InP photodiode and silicon nitride (Si₃N₄) microcavity solitons. The chip delivers mmWaves with −18dBm of electrical power at a frequency of 98 GHz with kHz-class linewidth and low phase noise and marks a significant advancement in on-chip photonic mmWave source performance. This breakthrough not only demonstrates capabilities of heterogeneous photonic integration but also offers a compact and scalable solution for future low-noise mmWave applications in communications and sensing technologies. 

We demonstrate InGaAs/InAlGaAs/InP waveguide photodiodes on Si₃N₄with up to 81 GHz 3-dB bandwidth, 0.76 A/W responsivity, and -1.8 dBm and -9 dBm output RF power at 50 GHz and 100 GHz, respectively. 

Radio-frequency (RF) waveform synthesis has broad applications in ultrawide-bandwidth wireless communications, radar systems, and electronic testing. Photonic-based approaches offer key advantages in bandwidth and phase noise thanks to the ultrahigh optical carrier frequency. In this work, we demonstrate Fourier synthesis arbitrary waveform generation (AWG) with integrated optical microresonator solitons. The RF temporal waveform is synthesized through line-by-line amplitude and phase shaping of an optical soliton microcomb, which is down-converted to the RF domain through dual-comb optical coherent sampling. A variety of RF waveforms with tunable repetition cycles are shown in our demonstration. Our approach provides not only the possibility of precise Fourier synthesis at microwave and millimeter-wave frequencies, but also a viable path to fully integrated photonic-based RF AWG on a chip.