The spectrally modulated self-coherent camera (SM-SCC): Increasing throughput for focal-plane wavefront sensing

TL;DR

The paper introduces the spectrally modulated self-coherent camera (SM-SCC), a novel wavefront sensing method that significantly enhances throughput and sensitivity for exoplanet imaging by using spectral modulation and an integral field unit.

Contribution

It proposes the SM-SCC design, which increases throughput by a factor of 32 and improves wavefront sensing sensitivity, enabling better contrast in exoplanet detection.

Findings

SM-SCC increases pinhole throughput by 32 times.

Achieves contrast of 1e-9 for bright targets in simulations.

Reaches photon-noise-limited contrast of 1e-7 for fainter targets.

Abstract

The detection and characterization of Earth-like exoplanets is one of the major science drivers for the next generation of telescopes. Current direct imaging instruments are limited by evolving non-common path aberrations (NCPAs). The NCPAs must be compensated for by using the science focal-plane image. A promising sensor is the self-coherent camera (SCC). An SCC modifies the Lyot stop in the coronagraph to introduce a probe electric field. However, the SCC has a weak probe electric field due to the requirements on the pinhole separation. A spectrally modulated self-coherent camera (SM-SCC) is proposed as a solution to the throughput problem. The SM-SCC uses a pinhole with a spectral filter and a dichroic beam splitter, which creates images with and without the probe electric field. This allows the pinhole to be placed closer to the pupil edge and increases the throughput. Combining the SM-SCC with an integral field unit (IFU) can be used to apply more complex modulation patterns to the pinhole and the Lyot stop. A modulation scheme with at least three spectral channels (e.g. IFU) can be used to change the pinhole to an arbitrary aperture with higher throughput. Numerical simulations show that the SM-SCC increases the pinhole throughput by a factor of 32, which increases the wavefront sensor sensitivity by a factor of 5.7. The SM-SCC reaches a contrast of $1\cdot10^{-9}$ for bright targets in closed-loop control with the presence of photon noise, phase errors, and amplitude errors. The contrast floor on fainter targets is photon-noise-limited and reaches $1\cdot10^{-7}$. For bright targets, the SM-SCC-IFU reaches a contrast of $3\cdot10^{-9}$ in closed-loop control with photon noise, amplitude errors, and phase errors. The SM-SCC is a promising focal-plane wavefront sensor for systems that use multiband observations, either through integral field spectroscopy or dual-band imaging.