Microfabricated pinholes for high contrast imaging testbeds

TL;DR

This paper presents the design, fabrication, and simulation of microfabricated pinholes for high-contrast imaging testbeds, demonstrating waveguide-like behavior to improve coronagraph source optics.

Contribution

It introduces a novel microfabrication process for pinholes and verifies their optical behavior through FDTD simulations and experimental characterization.

Findings

FDTD simulations show waveguide-like behavior of pinholes

Successful fabrication of aluminum overcoated silicon nitride pinholes

Characterization confirms the designed optical properties

Abstract

In order to reach contrast ratios of $10^{-8}$ and beyond, coronagraph testbeds need source optics that reliably emulate nearly-point-like starlight, with microfabricated pinholes being a compelling solution. To verify, a physical optics model of the Space Coronagraph Optical Bench (SCoOB) source optics, including a finite-difference time-domain (FDTD) pinhole simulation, was created. The results of the FDTD simulation show waveguide-like behavior of pinholes. We designed and fabricated microfabricated pinholes for SCoOB made from an aluminum overcoated silicon nitride film overhanging a silicon wafer substrate, and report characterization of the completed pinholes.