Low SWAP frequency combs for RF photonic chips and portable atomic clocks enabled by black phosphorus actives

Position, Navigation, and Timing (PNT) is critical in both commercial and defense sectors, affecting areas such as microwave communications, navigation, reconnaissance, and electronic warfare (EW). Precise digital conversion of multi-GHz analog signals, typically done through analog-to-digital converters (ADCs) is of paramount importance. However, state of the art electronic ADCs are reaching saturation due to fundamental limits on electronic timing jitter. Photonic ADCs, which perform sampling using ultra-precise signals from optical frequency combs have been explored as a promising approach to overcome the jitter problem and elevate ADC performance to new levels of precision. Consequentially, the US Air Force has Defense Need for the driver engine for the photonics ADC, specifically a photonic chip optical frequency comb (OFC) to integrate with photonic ADC systems, a critical technology for PNT. Current state-of-the-art commercial clocks are based on fiber-based boxes, unsuitable for integration. To overcome this, in this STTR Phase II, Iris Light and the University of Arizona propose to develop a new class of chip-scale optical frequency combs. A unique technical enabler is the integration of an on-chip saturable absorber based on proprietary semiconductor photonic inks.In Phase I, Iris Light and the University of Arizona (UA) validated the need and specifications required for frequency combs in photonic ADC systems with Air Force stakeholders. Preliminary data of on-chip, waveguide saturable absorbers was obtained, de-risking the technical pathway. Further, a preliminary system-level design to identify gaps in existing foundry components was created. In Phase II, sub-system prototypes, including the on-chip saturable absorbers, will be delivered throughout the Phase II project to ensure continuous feedback from Air Force stakeholders. The main deliverable is a prototype frequency comb chip at 1550 nm with multi-gigahertz rates suitable for integration into existing Air Force photonic chip systems. These devices will serve as building blocks for photonic PNT systems for the Air Force and beyond. More broadly, the ultra-low jitter photonic chip engine will enable the transition to next generation high fidelity ADCs with unprecedented bit precision.