Photonic mid-infrared nulling for exoplanet detection on a planar chalcogenide platform

TL;DR

This paper explores mid-infrared nulling interferometry using chalcogenide glass on a planar platform to improve exoplanet detection by achieving higher null depths, crucial for distinguishing planets from stellar light.

Contribution

It demonstrates a 20 dB null using chalcogenide glass and discusses methods to reach the theoretical 60 dB null depth for better exoplanet imaging.

Findings

Achieved 20 dB null depth with chalcogenide interferometer.

Identified scattering as a limiting factor for null depth.

Proposed measures to reach 60 dB null depth.

Abstract

The future of exoplanet detection lies in the mid-infrared (MIR). The MIR region contains the blackbody peak of both hot and habitable zone exoplanets, making the contrast between starlight and planet light less extreme. It is also the region where prominent chemical signatures indicative of life exist, such as ozone at 9.7 microns. At a wavelength of 4 microns the difference in emission between an Earth-like planet and a star like our own is 80 dB. However a jovian planet, at the same separation exhibits 60 dB of contrast, or only 20 dB if it is hot due to its formation energy or being close to its host star. A two dimensional nulling interferometer, made with chalcogenide glass, has been measured to produce a null of 20 dB, limited by scattered light. Measures to increase the null depth to the theoretical limit of 60 dB are discussed.