Everyday Life, Improved by Light: GRYPHON’s Photonic Discoveries

Radio frequency (RF) and microwave signals are integral carriers of information for technology that enriches our everyday life - cellular communication, automotive radar sensors, and GPS navigation, among others. At the heart of each system is a single-frequency RF or microwave source, the stability and spectral purity of which is critical. While these sources are designed to generate a signal at a precise frequency, in practice the exact frequency is blurred by phase noise, arising from component imperfections and environmental sensitivity, that compromises ultimate system-level performance.

This reality drives undesirable tradeoffs between performance, environmental sensitivity, and size that make the simultaneous achievement of stability, precision, and agility in an ultra-compact form factor an elusive feat. However, DARPA's Generating Radio Frequency with Photonic Oscillators for Low Noise (GRYPHON) program could change all of that, as performers recently demonstrated in the first phase of the program aimed at developing compact, ultra-low-noise microwave frequency oscillators.

While extremely low phase noise sources do exist, they are expensive, lack tunability, and are impractically large for deployment on mobile platforms that would enable advanced sensing and communication applications. GRYPHON seeks to change this paradigm by realizing viable, small-footprint microwave sources that transcend today's tradeoffs and far exceed current state of the art. Launched in January 2022, the program builds on advances in optical frequency division, integrated photonics, and non-linear optics - including those from previous DARPA efforts - to establish a new technology regime that transforms military and commercial capabilities.

GRYPHON performers, using different light-based approaches, have made critical progress towards generating high-purity microwaves in significantly reduced form factors. By integrating low-noise lasers with complex optical structures on low-loss photonic platforms, along with high-speed integrated circuits, researchers have established the viability of achieving ultra-low phase noise performance and shrinking these capabilities from conventional table-top sizes down to microchip-size form factors.

"The results and impact from Phase 1 of GRYPHON really show what's possible. For the first time, we're seeing how integrated photonics allows us to break from the traditional size vs. performance vs. capability trade space and operate in a regime with exquisite performance that is exponentially better than current state of the art," said Dr. Justin Cohen, GRYPHON program manager. "Better and faster communications, more accurate sensing, improved detection capabilities - this work could disrupt and advance countless applications."

The research findings of GRYPHON's performers were recently featured in Science and Nature journal articles, as well as via the National Institute of Standards and Technology, highlighting the work of contributing NIST researchers and their team. Now in Phase 2, GRYPHON researchers are seeking to further reduce phase noise in their already high-performance sources while introducing tunability and compactifying to targeted form factors, all of which aim to provide systems with unprecedented utility and access to previously unattainable applications.

Nature: Photonic chip-based low-noise microwave oscillator; Integrated optical frequency division for microwave and mmWave generation; All-optical frequency division on-chip using a single laser

Science: Multimodality integrated microresonators using the Moiré speedup effect