Photonic Signal Generation in Microwave and Millimeter-Wave Communications

Photonic signal generation harnesses optical methods to produce microwave and millimetre-wave carriers with frequencies from a few gigahertz up to and beyond 100 GHz. Key techniques include optical heterodyning of two laser tones, frequency comb modulation, Fourier-domain mode-locked lasers and optically injected semiconductor lasers. By converting broadband or chirped optical pulses into electrical signals at a photodetector, these approaches overcome the limitations of purely electronic sources, delivering ultra-low phase noise, wide instantaneous bandwidths and agile frequency tuning. Advances in integrated photonics—such as silicon micro-disk resonators and on-chip comb generators—have driven miniaturisation and improved stability. Applications span 5G/6G mobile backhaul, high-resolution radar and remote sensing systems, where large time-bandwidth products enable millimetre-scale range resolution and flexible waveform synthesis for dynamic spectrum sharing.

Research from Nature Portfolio

Recent studies have employed a hybrid Fourier-domain mode-locked laser incorporating a silicon photonic micro-disk resonator to generate linearly chirped microwave waveforms. By mode locking in the frequency domain, a broadband optical pulse is synthesised and then heterodyned with a continuous-wave carrier at a photodetector. This yields microwave signals exceeding 50 GHz of instantaneous bandwidth and 30 µs temporal duration, achieving time-bandwidth products above 1.5 × 10^6. The platform offers rapid electrical tuning of centre frequency, chirp rate and pulse duration, demonstrating a compact and reconfigurable route to ultra-wideband, low-phase-noise sources suitable for next-generation radar and high-capacity wireless links.

Photonic Signal Generation in Microwave and Millimeter-Wave Communications publication trend

The graph below shows the total number of articles in photonic signal generation in microwave and millimeter-wave communications across all publications each year (not limited to Nature Index journals).

Technical terms

Optical heterodyning: Generation of a microwave or millimetre-wave signal by beating two optical tones at a photodetector.

Time-bandwidth product (TBWP): The product of signal duration and instantaneous bandwidth, indicating the achievable resolution or information content.

Single-sideband modulation (SSB): A modulation scheme that suppresses one optical sideband to alleviate photodetector bandwidth limitations and unwanted image frequencies.

Fourier-domain mode locking (FDML): A laser operating regime where wavelength-selective filtering within a loop cavity produces rapid frequency sweeps and broadband optical pulses.

Photodetector (PD): A semiconductor device that converts incident optical signals into electrical microwave or millimetre-wave outputs.

References

1. Photonic generation of ASK microwave signals with SSB format. Frontiers of Optoelectronics (2023).
2. Linearly chirped microwave waveform generation with large time-bandwidth product by optically injected semiconductor laser.. Optics Express (2016).
3. Photonic generation of W-band arbitrary waveforms with high time-bandwidth products enabling 3.9  mm range resolution. Optica (2014).
4. Hybrid Fourier-domain mode-locked laser for ultra-wideband linearly chirped microwave waveform generation. Nature Communications (2020).