Frequency-Agile Combs on the Tantala and Lithium Niobate Platform (FRACTAL)

Several next-generation approaches to precision navigation and timing (PNT) and low-noise microwave generation for radar require electro-optic frequency combs (EO comb) that have dramatically reduced size, weight, and power consumption (SWaP). However, the SWAP (and cost) of current commercial EO combs is limited by the need to drive a series of EO modulators with high-power RF amplifiers in order to generate the >5 nm of bandwidth required for many applications. Builders of EO combs are hampered by the lack of appropriate modulators, while manufacturers of modulators are typically not responsive to requirements of EO combs: low V-pi, high power handling, and low cost-per-comb-tooth. To address this critical need, Octave Photonics (OP), in collaboration with MIT Lincoln Laboratory (LL), is proposing to develop Frequency-Agile Combs on the Tantala and Lithium-Niobate Platform (FRACTAL). The FRACTAL program will combine the expertise of these two organizations to bridge the gap between nanophotonic EO modulator design and the production of practical EO comb devices. Over recent years, LL has developed a thin-film lithium niobate platform and has demonstrated promising results towards low V-pi modulators. The thin-film LN technology developed at LL will be combined with the tantala platform and nanophotonic packaging technologies in use at Octave Photonics. Additionally, Octave Photonics is a world leader in the development and commercialization of EO combs. Combined, the two organizations possess the required expertise to produce cutting-edge modulators tailored for EO comb generation, combine these modulators with tantala waveguides, package the resulting nanophotonic chips into stand-alone modulator devices, and integrate these modulators into complete EO comb systems. The resulting EO comb products will substantially outperform Octave’s existing commercial offerings in terms of SWaP and cost. The FRACTAL Phase I project will involve several key studies and demonstrations to assess the feasibility of this approach. First, we will work closely the Air Force customer to understand how our technologies can best align with their exact requirements. Second, we will conduct simulations to understand how we can achieve low V-pi in practical modulator designs. Third, modulators will be evaluated at the Octave facilities and assessed in their ability for EO comb generation. Fourth, we will develop an extensive plan for how the LN and tantala nanofabrication processes will be integrated. Finally, we will conduct a demonstration of packaging a LN modulator chip into a robust fiber-coupled package. The results of these studies will enable us to make a well-informed plan for how the FRACTAL platform can be best implemented.