Collaborative Research: Mastering the photonic lantern: The key to transformative diffraction-limited spectroscopy

This project aims to advance a key technology known as a “photonic lantern.” Photonic lanterns will allow for compact and stable spectrographs behind large telescopes. These spectrographs will deliver extremely precise measurements of various astronomical objects, most notably planets around other stars. The work to advance photonic lanterns will proceed in several key ways.

First, to understand how to use lanterns to efficiently capture light from a large telescope. Second, to demonstrate that lanterns can sense the shape of light waves after they are affected by Earth’s atmosphere. This will enable correction for those shape errors and maximize the amount of light captured.

Finally, to explore the potential of using a lantern for making images and measuring positions of astronomical objects. This work will also be directly applicable to telecommunications and free-space optical communications. Lanterns could play a key role in increasing the data volume and fidelity of data transfer with satellites.

Operating at the diffraction-limit breaks traditional seeing-limited instrument scaling laws and allows a spectrograph to be the most compact for a given set of specifications. A compact instrument uses optics that are more likely to be manufacturable and of higher quality, is more robust to mechanical deflections, easier to thermally stabilize, and costs less.

A Photonic Lantern (PL) allows conversion of a multi-mode fiber input to multiple single-mode fibers, thus enabling greater coupling at the input while maintaining the diffraction-limit into the spectrograph thus maintaining an ultra-stable spectral line-spread function (i.e. the shape does not vary with time or input illumination conditions). The project seeks to understand how to efficiently inject light into PLs from wavefronts partially corrected by adaptive optics.

Further it will investigate if PLs can be used as focal-plane wavefront sensors, eliminating non-common path and chromatic errors, and boosting system efficiency Finally, the ability to use lanterns to do imaging and astrometry by separating the coherent and incoherent parts of the electric field will be investigated. The outcomes from this project could have immediate significant impact on existing and future spectrographs on large telescopes.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.