The Department of Defense (DoD) is seeking proposals for the development of a turn-key micro optical-frequency-comb module, aimed at enhancing low-noise and stable microwave sources critical for various applications in RF EW/Radar, data communication, and long-range detection systems. The objective is to create a miniature optical frequency comb module that is low in size, weight, and power (SWaP), which includes an external pump-laser fitting within a standard 14-pin butterfly package, along with control electronics. This initiative is significant as it addresses current barriers in system integration and supports advancements in photonics research, with potential applications across multiple sectors including RF electronics, precision navigation and timing, and automation. Proposals for Phase I are due by June 25, 2025, with a funding limit of $250,000 for a six-month performance period, and interested parties can find more information at the DoD SBIR website.

## Description

Low-noise and stable microwave sources are a critical component in RF EW/Radar, data communication, and long-range detection/sensing systems for fast response and precision targeting. The Nobel prize winning optical frequency comb provides a phase-coherent connection between optical and microwave domains that can be configured as precision microwave oscillator. Recent advances in integrated photonics have enabled chip-scale photonic micro-resonator frequency combs, or microcombs, a miniature precision frequency source with low SWaP-Cost (SWaP-C) able to fit into smaller platforms (UAVs). Microcombs have evolved quickly from early laboratory demonstrations to more advanced devices that are being explored in multiple DoD applications including microwave synthesis in Radar and EW system, timing for a PNT system, high-bandwidth data communication and bio-chem sensing. Very recently, a new generation of microcombs has been reported that enable turnkey, direct semiconductor laser pumping. The pump laser frequency is self-injection locked by the microcomb; therefore, it does not require special triggering mechanisms such as pump laser frequency or amplitude kicking techniques for soliton generation, making them significantly more reliable and user friendly. For the first time, fully functional and turnkey microcomb modules operating at X and K-band repetition-rates are feasible. These modules could incorporate features that enable multi-modality operation, electronic control and user diagnostics. As low-SWAP-C, fully packaged systems, they would find immediate applications within the DoD. Furthermore, their existence would accelerate development of critical systems by removing a current entry barrier to system integrators. Access to microcomb devices with such a full spectrum of features would also support the photonics research community, enabling a new generation of photonics systems development.

## Objective

This topic seeks to research and develop a low size, weight, and power (SWaP), soliton-based miniature optical frequency comb module. The goal is to deliver a turn-key microcomb-based prototype including an external pump-laser that fits within an industry standard 14-pin butterfly package with control electronics board. 

## Phase I

This topic is only accepting Phase I proposals for a cost up to $250,000 for a 6-month period of performance. A successful proposal will address challenges associated with pump power and modal volume in self-injection locked microcombs and take advantage of industry standard fabrication techniques found in CMOS foundries within the US. For the Phase 1 effort the team will design the microcomb source. The design will include a micro-resonator design and layout for foundry fabrication; design of the pump-laser module and photonic interconnects to the micro-resonator chip; model the packaging layout; design the control electronics module. The team will also provide a manufacturing plan describing how they would support large volume fabrication and packaging. Finally, the team will conduct initial laboratory bench-top experimental tests demonstrating comb generation and verifying frequency and stability metrics.

## Phase II

Building on Phase 1 design work the team will proceed with the fabrication of the microcomb module and assembly of two microcomb modules (minimum) with their associated control modules. Prototype devices will be fully tested for comb generation, stabilization and tunability for locking purposes. At the end of Phase II, the team will deliver two fully functional microcomb units along with all associated testing data and an operation manual. Prototype devices will meet the following requirements: <ul><li>Microcomb module including an external pump laser in an industry standard 14-pin butterfly package </li><li>Electronic control module using a single power source </li><li>Whole unit within 10 cc volume </li><li>Complete turnkey operation (simple on/off switch) </li><li>Comb repetition rates: between 10 to 40 GHz. </li><li>Comb repetition rate and Carrier envelop frequency (fCEO ) can be independently tuned by external signals, each with a bandwidth of at least 10 kHz. </li><li>Microcomb bandwidth: 30 nm for 20 GHz comb, 60 nm for 40 GHz comb </li><li>Power consumption: Optical Module (2 W) Electrical Control Module (3 W)</li></ul>

## Phase III: Dual Use Applications

<ol><li>RF Electronics (including microelectronics, Radars, wireless communications) </li><li>PNT (including precision clocks for timekeeping, precision distance measurement/ranging) </li><li>Computing and Data communication (high-speed computing and data communication, data center) </li><li>Spectroscopy (Bio medical and chemical sensing, spectroscopy instruments) </li><li>Automation (UAVs and drones) </li><li>Space (satellites, spacecrafts) </li><li>Astronomy (synchronized Radar and detection system, frequency spectroscopy)</li></ol>

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