Laboratory demonstration of an all-fiber-based focal plane nulling interferometer

TL;DR

This paper demonstrates a fiber-based nulling interferometer in the lab, using commercial components to suppress starlight for exoplanet imaging, with promising preliminary results and plans for on-sky testing.

Contribution

It introduces a novel all-fiber nulling interferometer utilizing commercially available components for amplitude and phase control.

Findings

Successful lab demonstration at 632 nm

Effective amplitude matching with MEMS VOA

Optical path difference control with fiber stretcher

Abstract

Starlight suppression techniques for High-Contrast Imaging (HCI) are crucial to achieving the demanding contrast ratios and inner working angles required for detecting and characterizing exoplanets with a wide range of masses and separations. The advent of photonic technologies provides new opportunities to control the amplitude and phase characteristics of light, with the potential to enhance and control starlight suppression. Here, we present a focal plane optical-fiber-based nulling interferometer working with commercially available components for amplitude and phase modulation. The instrument implements single-mode fiber-coupled elements: a MEMS variable optical attenuator (VOA) matches the on-axis and off-axis starlight amplitude, while a piezoelectric-driven fiber stretcher modifies the optical path difference between the channels to achieve the $\pi$ phase shift condition for destructive interference. We show preliminary lab results using a narrowband light source working at 632 nm and discuss future opportunities for testing on-sky with the Astrophotonics Advancement Platform at Lick Observatory (APALO) at the Shane 3-m Telescope.