Firefly Photonic Mid-IR Nulling Interferometer

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The backbone of a Nuller is a cascaded series of Multimode Interference Couplers.

The Firefly project is a CUDOS initiative to fabricate, test, and deploy an on-chip Nulling Interferometer which operates in the Mid-Infrared wavelengths (4 um).

A Nulling interferometer, or “Nuller”, uses active control of the phase of the light as it propagates in a waveguide to create destructive interference of the starlight and hence ‘null’ it out. This capability is incredibly advantageous to astronomy because if there is light from the star’s faint companion, say a planet, the planet’s light remains unaffected by the Nuller as the planet and star are not coherent with each other. Thus, by suppressing the starlight and allowing the planet light to continue through the system, we can perform direct measurements and imaging on the planet itself.

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A series of Bracewell Nullers running vertically on one of our recently fabricated wafers. Using the lithographic platform we are able to make hundreds of Nullers on a single wafer.

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Edge-on view looking into one of the Mid-IR waveguides.

To create viable photonic Nullers for astronomical use, they must have low insertion and propagation losses, as well as be able to operate in a broad wavelength window.

Leveraging the years of CUDOS experience in lithographic fabrication of Mid-IR photonics, Firefly is being manufactured using the Chalcogenide platform at the ANU CUDOS node. By enhancing the techniques employed on previous CUDOS projects, we are able to produce low-loss waveguides, with large mode sizes to allow for the injection of starlight on a telescope.

For information on Masters and PhD projects available on the Firefly project, contact

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