The Dispersion Leverage Coronagraph (DLC): A nulling coronagraph for use on primary objective grating telescopes

TL;DR

The paper introduces the Dispersion Leverage Coronagraph (DLC), a novel nulling coronagraph designed for dispersive optical systems like large diffraction grating telescopes, enabling high-resolution imaging and characterization of exoplanets.

Contribution

It develops the theoretical foundation of DLC and demonstrates its application to a space telescope concept, DICER, for exoplanet detection and characterization.

Findings

DLC effectively nulls on-axis targets across the spectrum.

DLC allows 2D/lambda diffraction-limited imaging.

Simulations suggest DICER could find ~4 habitable exoplanets within 8 pc.

Abstract

We present the Dispersion Leverage Coronagraph (DLC), a novel variation of the Achromatic Interfero Coronagraph (AIC) that is designed for optical systems featuring large, dispersive primary objective gratings. DLC was originally designed for the Diffractive Interfero Coronagraph Exoplanet Resolver (DICER), a notional 20m class infrared space telescope utilizing the enhanced one-dimensional angular resolution of large diffraction gratings in order to discover and characterize near-Earth exoplanets. Here we develop the theoretical foundation for DLC, and apply it to DICER as an example use case. We derive important properties of the DLC system including focal plane transmission maps, stellar leakage, residual optical path difference tolerance, and pointing error/jitter considerations. Ultimately, we found that DLC effectively nulls an on-axis target across the entire spectrum in the focal plane, allowing for 2D/lambda diffraction-limited imaging. It requires asymmetrical fine-guidance tolerances on pointing error/jitter. We work through a benchmark DICER design, explaining the need for a second disperser to reduce background from Zodiacal light, and showing that it could plausibly find and characterize approximately 4 nearby, habitable exoplanets around Sun-like stars in a seven year mission; about 30% of the habitable exoplanets within 8 pc were found in our simulation. The DLC may be useful for any application requiring extremely high resolution, close-companion spectroscopy.