Military laser communications experts reach out to industry for new optical materials for free-space optics

ARLINGTON, Va. – U.S. military laser communications experts are reaching out to industry to develop new kinds of tunable optical materials for low-loss and fast-switching free-space optics, integrated photonics, and emissivity-control applications.

Officials of the U.S. Defense Advanced Research Projects Agency (DARPA) in Arlington, Va., issued a disruption opportunity last week for the Accelerating discovery of Tunable Optical Materials (ATOM) project.

ATOM seeks to identify materials operating over broad spectral bandwidths in the visible, midwave infrared, and longwave infrared spectra.

Most tunable optics applications could use an optical material with a large change in refractive index for delay light, low loss for high transmissivity, and fast switching speeds, DARPA researchers explain.

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Different material speeds are of interest, and operating in several optical states is important for applications such as aberration correction in optical imaging systems.

Researchers would like to apply tunable optical materials to integrated photonics and free-space optics applications in the infrared spectrum. Here, the best choice involves phase change materials, which can be switched between amorphous and crystalline states with thermal energy.

A common phase change material, germanium-antimony-tellurium has considered as a tunable optical material because its switching time is faster than 10 microseconds, and it has large index contrast. The material, however, exhibits debilitating loss below the short-wave infrared, limiting its utility in short-wavelength applications.

The goal of the ATOM program is to discover new tunable optical materials with large refractive index contrast across the full band, with low loss and fast switching times, and to demonstrate a device with a minimum area of 250 square microns, capable of achieving repeatable, stable multi-state switching while maintaining bandwidth and performance.

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Achieving these goals will require predictive modeling and materials optimization; careful navigation of the materials market; and charting index contrast, loss, and switching speed. An increased understanding in material failure mechanisms and switching behavior also is necessary to produce materials with long switching lifetimes and minimal variance across switching cycles.

Proposers clearly should identify:

-- their preferred materials discovery technique and predictive modeling approach;

-- candidate materials and how those materials navigate the materials market;

-- how they will investigate failure mechanisms and optimize stability in various film thicknesses;

-- how to develop tunable optical materials with high index contrast, low loss, and non-volatile switching in the visible light spectrum;

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-- new materials for phase change materials that have not been explored or even discovered for the infrared spectrum;

-- if non-thermal switching mechanisms have sufficient index modulation with low loss;

-- the fundamental materials physics the influence the durability of tunable materials; and

-- the behavior scale with film thickness.

ATOM will be a two-year effort with a yearlong discovery phase and a yearlong demonstration phase. The first phase will identify and characterize new tunable optical materials and predictive modeling tools. The second phase will demonstrate the new material as a switchable film over more than 10 index states.

Companies interested should upload proposals no later than 30 June 2023 to the DARPA BAA website at https://baa.darpa.mil. Email questions or concerns to Rohith Chandrasekar, the DARPA ATOM program manager, at [email protected]. More information is online at https://sam.gov/opp/b0a46e3ae88142ba9b7c5715c01f675b/view.