Millimetre-wave (mmWave) technology continues to draw great interest due to its broad applications in wireless communications, radar, and spectroscopy. Compared to pure electronic solutions, photonic-based mmWave generation provides wide bandwidth, low power dissipation, and remoting through low-loss fibres. However, at high frequencies, two major challenges exist for the photonic system: the power roll-off of the photodiode, and the large signal linewidth derived directly from the lasers. Here, we demonstrate a new photonic mmWave platform combining integrated microresonator solitons and high-speed photodiodes to address the challenges in both power and coherence. The solitons, being inherently mode-locked, are measured to provide 5.8 dB additional gain through constructive interference among mmWave beatnotes, and the absolute mmWave power approaches the theoretical limit of conventional heterodyne detection at 100 GHz. In our free-running system, the soliton is capable of reducing the mmWave linewidth by two orders of magnitude from that of the pump laser. Our work leverages microresonator solitons and high-speed modified uni-traveling carrier photodiodes to provide a viable path to chip-scale, high-power, low-noise, high-frequency sources for mmWave applications.

We demonstrate high speed and high power evanescently-coupled waveguide integrated modified uni-traveling-carrier (MUTC) photodiodes. Over 105 GHz bandwidth along with 2 dBm and 1.3 dBm RF output power at 100 GHz and 105 GHz, respectively, has been achieved.

This paper reviews high-power photodiodes, waveguide photodetectors, and integrated photodiode-antenna emitters with bandwidths up to 150 GHz. Results from heterogeneous III-V photodiodes on silicon and Ge-on-Si photodiode arrays for analog applications are presented.

High-linearity modified uni-traveling carrier photodiodes on silicon-on-insulator with low AM-to-PM conversion factor are demonstrated. The devices deliver more than 2.5 dBm RF output power up to 40 GHz and have an output third order intercept point of 30 dBm at 20 GHz. Photodiode arrays exceed a saturation current-bandwidth-product of 630 mA·GHz and reach unsaturated RF output power levels of 10 dBm at 20 GHz.

Top-illuminated PIN and modified uni-traveling carrier (MUTC) photodiodes based on InGaAs/InAlAs/InP were epitaxially grown on Si templates. Photodiodes with 30-μm diameter have dark currents as low as 10 nA at 3 V corresponding to a dark current density of only 0.8 mA/cm². The responsivity, 3-dB bandwidth, output power and third-order output intercept point (OIP3) were 0.79 A/W, 9 GHz, 2.6 dBm and 15 dBm, respectively.

Waveguide-integrated photodiodes with InGaAs/ GaAsSb type-II quantum well absorption regions designed to absorb light at 2 μm are presented. A novel dual-integrated waveguide-depletion layer was used to maximize quantum efficiency in photodiodes designed with thin absorbers for high-speed optical response. Low dark currents (1 nA at -1 V) and an internal responsivity of 0.84 A/W along with a bandwidth above 10 GHz and an open eye diagram at 10 Gb/s have been demonstrated at 2 μm. The high-speed carrier dynamics within InGaAs/GaAsSb type-II quantum wells are explored for the first time and suggest that the transit time of the photodiode is limited by light hole escape times in the quantum wells.