Collaborative Research: Developing optimally customized-mode-selective photonic lanterns to enable the characterization of hundreds of exoplanets on solar system.

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There are currently more than 5,000 confirmed planets orbiting stars other than our Sun. Being able to separate and analyze the colors of light from these planets would provide a wealth of information, including for example allowing for the measurement of composition and abundance of various molecules, to study circulation (weather) patterns, and to indicate the presence of moons. The key to being able to carry out such characterizations is the ability to isolate the extremely faint planetary light from the bright glare of the star the planet orbits around. Unfortunately, of the 5,000+ confirmed exoplanets, only about 1 in 100 have been characterized like this, and none of those are orbiting their host stars within orbits the size of our solar system. This project aims at advancing a key technology known as a “photonic lantern” for the purpose of eliminating contaminating starlight so that an exoplanet (a planet orbiting another star) can be isolated and characterized within the angular resolution limit of the telescope. The investigators will look into unique designs of photonic lanterns to maximize the effect of nulling (starlight suppression) and stability in tandem with other technologies. This project supports training of the next generation of instrument designers by providing unique opportunities for students to work at cutting edge facilities on 8-m class telescopes. The Vortex Fiber Nuller (VFN), recently commissioned within the KPIC instrument on the Keck Telescope, is an example of an instrument incorporating new technology. It utilizes a pupil-plane vortex mask followed by a focal-plane single-mode fiber (SMF) to reject starlight and accept planet light with ~19% transmission at 1 λ/D separation. If the SMF were replaced with a 6-port hybrid mode-selective photonic lantern (PL), the total planet throughput would be increased by ~2x, and its location and brightness constrained. Both are impossible with the current SMF VFN approach. In addition, the PL enables focal-plane wavefront sensing (WFS), eliminates non-common path and chromatic errors, thus deepening and stabilizing the null. Utilizing a PL for nulling extends the reach of VFN to allow hundreds of giant exoplanets to be directly characterized, providing a robust sample in the study of planet formation. We propose to develop novel hybrid and mode-selective PLs for optimal on-board WFS and nulling with 8-10 m 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.