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Tunable, Integrated Electro-optic Frequency Comb for Space-based Communications and Precision, Navigation and Timing (PNT) Applications


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Integrated Sensing and Cyber;Human-Machine Interfaces


The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.


OBJECTIVE: Design, fabricate, and demonstrate a photonically integrated electro-optic modulator capable of generating an optical frequency comb with 1-10 GHz spacing in the 1540-1560 nm band.


DESCRIPTION: Optical frequency combs, including electro-optic-generated optical frequency combs [1], have been a revolutionary technology across many areas, including a host of applications in spectroscopy, communications, and Position, Navigation and Timing (PNT).  Photonically integrated electro-optic modulator platforms [2] offer the potential for robust, chip-scale, optical frequency comb generation with full electrical control, and the eventual deployment of comb technologies into mobile and space-based applications.  The recent emergence of new integrated modulator material platforms, such as thin film lithium niobate [3] and barium titanate [4], as well as novel modulator designs offer the potential for enhanced efficiency, bandwidth, and packaging [5 - 7] to fully exploit the potential of optical frequency combs outside of the laboratory. These advances warrant further investigation into photonically integrated electro-optic modulators as well as their packaging, with an emphasis on a reduction in Vpi, high conversion efficiency, low waveguide propagation and insertion loss, and high optical and RF power handling.


PHASE I: Develop a platform fabrication and integration plan with supporting preliminary results (i.e., measurements, modeling/simulation, etc.) toward realizing the Phase II device specfications and deliverables.  Material platform(s), pump-to-comb conversion efficiency and insertion losses with a full power budget should be included.  Low RF power modulator driving requirements are desirable.  Proposals should include a plan to either generate and characterize optical frequency comb performance or to provide full modulator characterization to predict comb performance.  Phase I deliverables include a final report motivating the platform fabrication and integration plan.


PHASE II: Phase II will include fabrication and testing of prototype integrated modulator devices demonstrating:  • tunability of phase and amplitude to support frequency comb generation and control with 1 - 10 GHz line spacing; • low Vpi (< 1 V) and RF power requirements (proposal should identify anticipted Vpi and modulator power requirements) across the 1 - 10 GHz tuning range supporting 5 nm broad electro-optic comb generation at 1 GHz repetition rate within the 1540 - 1560 nm band; • low waveguide to modulator coupling losses (proposals should identify anticipated coupling losses); • polarization maintaining fiber-coupled interconnects for coupling onto and off from the integrated chip-scale modulator platform; • high optical power handling (>500 mW of input power) at desired wavelengths.  Phase II prototypes should include all necessary electronics to support modulator operation and thermal control.  Electronics may reside off chip (on-chip integration is desirable); however, a path should be identified for full integration, including projected power budget improvements.  Multiple devices demonstrating modulator uniformity are desirable.  At the completion of Phase II, four (4) prototype devices will be delivered to government laboratories of AFOSR's specification for characterization and integration with space-focused technology demonstrators. The final devices should be adequately packaged and integrated with all relevant supporting electronics for delivery to and operation by the test verification facility. Guidance/documentation for device operation should be provided for test facility personnel.  Deliverables include a final technical report, at least four (4) prototype devices and supporting documentation.  The Technology Readiness Level to be reached is 5: Component and/or bread-board validation in relevant environment.


PHASE III DUAL USE APPLICATIONS: Integrated optical frequency comb technology is anticipated to be broadly applicable across applications spanning the scientific, commercial, and defense domains, as evidenced by the impact of bulk-scale optical frequency comb technologies and the burgeoning impact of competing chip-scale comb technologies which currently offer less robustness, efficiency, and control.  Many of the same applications revolutionized by bulk-scale laboratory optical frequency comb technology may be accessible to integrated comb generation technologies at a size, weight, and power (SWaP), robustness, and level of control which allows for operation outside of the laboratory and potentially for optimized comb parameters in applications including communications. There will be a need to demonstrate foundry level fabrication and robust packaging techniques for large scale production as well as testing long term performance in environments such as large temperature fluctuations, high shock and vibration, and vacuum compatibility.




1. Advances in Optics and Photonics, 12, 223 (2020);

2. Journal of Semiconductors, 42, 041301 (2021);

3. Nature Communications, 11, 4123 (2020);

4. Optics Express, 12, 5962 (2004);

5. Nature Photonics, 16, 679 (2022);

6. Optics Express, 30, 23177 (2022);

7. Optica 9, 408-411 (2022)


KEYWORDS: RF Integrated Photonics, Integrated Optical Modulator, Electro-optic Device, Frequency Comb

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