Achromatic photonic tricouplers for application in nulling interferometry

TL;DR

This paper introduces an achromatic photonic tricoupler designed via ultrafast laser inscription, significantly improving broadband nulling interferometry by reducing phase fluctuations and chromaticity issues.

Contribution

The paper presents a novel achromatic tricoupler that addresses phase stability and chromaticity challenges in nulling interferometry, enhancing high-contrast astrophysical observations.

Findings

Order of magnitude improvement in null depth with the tricoupler

Effective mitigation of phase fluctuation effects

Reduction of chromaticity in directional couplers

Abstract

Integrated-optic components are being increasingly used in astrophysics, mainly where accuracy and precision are paramount. One such emerging technology is nulling interferometry that targets high contrast and high angular resolution. Two of the most critical limitations encountered by nullers are rapid phase fluctuations in the incoming light causing instability in the interference and chromaticity of the directional couplers that prevent a deep broadband interferometric null. We explore the use of a tricoupler designed by ultrafast laser inscription that solves both issues. Simulations of a tricoupler, incorporated into a nuller, result in order of a magnitude improvement in null depth.