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US military seeks tunable materials for low-loss integrated photonics

Satellite communications

Free-space optics will play an important role in future inter-satellite communication capabilities. (Image: Shutterstock/Gorodenkoff)

The US Defense Advanced Research Projects Agency (DARPA) Defense Sciences Office has issued a callout for new tunable optical materials (TOMs) operating over broad spectral bandwidths in the visible and mid-/long-wave infrared spectrums.

The materials will be used within the ATOM programme (Accelerating discovery of Tunable Optical Materials), which aims to discover and develop new TOMs that enable low-loss, high-switching-speed free-space optics, integrated photonics, and emissivity control applications. 

In general, most tunable optics applications require or would benefit from optical materials with: a large change in refractive index to delay light; low loss for high transmissivity; and fast switching speeds to meet most optical and photonic applications. The switching speeds required depend on the application. For example, aberration correction in optical imaging systems requires microsecond switching times, while tunable filters or emissivity control require millisecond switching. In general, fast switching is more broadly applicable. Being able to operate in multiple optical states is also important, particularly for aberration correction applications.

ATOM’s two main objectives are therefore:

  • To discover tunable visible or infrared materials with large refractive index contrast across the full band, with low loss and non-volatile fast switching
  • To demonstrate a device with a minimum area of 250µm2, capable of achieving repeatable, stable multi-state switching while maintaining the required bandwidth and performance 

The programme will run for two years, separated into two 12-month phases: a discovery phase and demonstration phase. The first will focus on the identification and characterisation of new TOMs meeting material property metrics using adaptive materials discovery and predictive modelling tools, while the second will focus on the experimental demonstration of the new material as a switchable film over more than 10 index states.

The programme also seeks to explore whether there are new mechanisms to tune optical materials that are not based on thermal modulation, and if these exhibit high index contrast, low loss, and fast switching. If there are indeed such non-thermal switching mechanisms, ATOM will also look to identify whether they have sufficient index modulation with low loss.

More information on the callout, which has been issued as a ‘Disruption Opportunity’, can be found using the ID: DARPA-PA-22-01-03. Those looking to participate must submit their proposals by 30 June. Given that the focus of the ATOM programme is to discover new TOMs that could enable a wide array of optic and photonic applications across the visible and IR, DARPA has expressed that proposed efforts to optimise known materials will be out of scope.


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