Photonics-Enabled Microwave and Terahertz Signal Generation

Photonics‐enabled generation of microwave and terahertz signals harnesses optical techniques to produce electronic carriers with unprecedented spectral purity, tunability and bandwidth. By down-converting ultrastable optical references through frequency combs or heterodyne beating, photonic systems achieve phase noise levels far below those attainable with purely electronic oscillators. Advances in integrated photonics, including microresonator soliton combs, self-injection-locked lasers and miniaturised optical reference cavities, have transformed bulky laboratory setups into chip-scale platforms. These developments underpin high-precision navigation, next-generation wireless communications, remote sensing, spectroscopy and mmWave radar. The global significance of this field lies in its potential to meet the stringent requirements of 5G/6G connectivity, high-resolution imaging and fundamental metrology, while reducing size, weight, power consumption and cost.

Research from Nature Portfolio

Recent studies have demonstrated full photonic integration of microwave oscillators on a single chip. One approach uses two self-injection-locked lasers stabilised to a miniature Fabry–Pérot cavity and a dark-soliton microcomb to divide optical frequency gaps, yielding a 20 GHz signal with phase noise as low as –135 dBc Hz–1 at 10 kHz offset. A complementary effort miniaturises optical frequency division by coupling planar-waveguide reference coils with soliton microcombs, achieving record-low phase noise for mmWave generation and paving the way for CMOS-compatible mass manufacture. In the terahertz domain, coherent photomixing of cavity-stabilised comb lines produces tunable outputs from 0.10 to 1.10 THz with ultra-low phase noise (–70 dBc Hz–1 at 1 Hz offset) and sub-10−15 frequency instability at one second, greatly enhancing spectroscopy, radar resolution and wireless capacity.

Photonics-Enabled Microwave and Terahertz Signal Generation publication trend

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

Technical terms

Frequency comb: A spectrum of discrete, equally spaced optical lines used as a ruler in frequency metrology and signal synthesis.

Microcomb: A frequency comb generated in a microresonator via Kerr nonlinearity, often producing soliton pulses.

Photonic integration: Monolithic or hybrid integration of lasers, modulators, resonators and detectors on a single chip.

Phase noise: Random fluctuations in the phase of an oscillating signal, expressed in dBc/Hz at a given offset.

Optical heterodyning: Generation of electronic frequencies by beating two optical tones on a photodiode.

Photomixing: Conversion of beat notes between optical frequencies into microwave or terahertz waves via photoconductive devices.

References

1. Photonic chip-based low-noise microwave oscillator. Nature (2024).
2. Integrated optical frequency division for microwave and mmWave generation. Nature (2024).
3. Photonic comb-rooted synthesis of ultra-stable terahertz frequencies. Nature Communications (2023).
4. A chip-integrated comb-based microwave oscillator. Light: Science & Applications (2025).
5. Small-sized, ultra-low phase noise photonic microwave oscillators at X-Ka bands. Optica (2023).
6. Present and future of terahertz integrated photonic devices. APL Photonics (2023).