Implicit Electric Field Conjugation Through a Single-mode Fiber

TL;DR

This paper introduces an implicit electric field conjugation (iEFC) wavefront control method for single-mode fibers, improving stellar light suppression in exoplanet observations without requiring detailed optical models.

Contribution

The paper presents a novel iEFC algorithm that outperforms classical EFC in high wavefront error conditions and does not depend on an optical system model.

Findings

iEFC achieves normalized intensity > 10^{-10} in simulations.

iEFC outperforms EFC by ~100x in high WFE scenarios.

Both methods perform similarly at low WFE.

Abstract

Connecting a coronagraph instrument to a spectrograph via a single-mode optical fiber is a promising technique for characterizing the atmospheres of exoplanets with ground and space-based telescopes. However, due to the small separation and extreme flux ratio between planets and their host stars, instrument sensitivity will be limited by residual starlight leaking into the fiber. To minimize stellar leakage, we must control the electric field at the fiber input. Implicit electric field conjugation (iEFC) is a model-independent wavefront control technique in contrast with classical electric field conjugation (EFC) which requires a detailed optical model of the system. We present here the concept of an iEFC-based wavefront control algorithm to improve stellar rejection through a single-mode fiber. As opposed to image-based iEFC which relies on minimizing intensity in a dark hole region, our approach aims to minimize the amount of residual starlight coupling into a single-mode fiber. We present broadband simulation results demonstrating a normalized intensity greater than 10^{-10} for both fiber-based EFC and iEFC. We find that both control algorithms exhibit similar performance for the low wavefront error (WFE) case, however, iEFC outperforms EFC by approximately 100x in the high WFE regime. Having no need for an optical model, this fiber-based approach offers a promising alternative to EFC for ground and space-based telescope missions, particularly in the presence of residual WFE.