Simulations of mode-selective photonic lanterns for efficient coupling of starlight into the single-mode regime

TL;DR

This paper demonstrates through simulations that mode-selective photonic lanterns can efficiently couple partially corrected starlight into fewer single-mode outputs, improving astronomical instrumentation.

Contribution

It introduces a mode-selective photonic lantern design and shows its effectiveness in reducing output channels for coupled starlight.

Findings

Two waveguides carry >95% of coupled light at D/r0 < 10

Mode-selective lanterns outperform non-selective ones in efficiency

Partial wavefront correction enhances coupling efficiency

Abstract

In ground-based astronomy, starlight distorted by the atmosphere couples poorly into single-mode waveguides but a correction by adaptive optics, even if only partial, can boost coupling into the few-mode regime allowing the use of photonic lanterns to convert into multiple single-mode beams. Corrected wavefronts result in focal patterns that couple mostly with the circularly symmetric waveguide modes. A mode-selective photonic lantern is hence proposed to convert the multimode light into a subset of the single-mode waveguides of the standard photonic lantern, thereby reducing the required number of outputs. We ran simulations to show that only two out of the six waveguides of a 1x6 photonic lantern carry >95% of the coupled light to the outputs at $D/r_0 < 10$ if the wavefront is partially corrected and the photonic lantern is made mode-selective.