HCIL

Full testbed name

High Contrast Imaging Laboratory (HCIL)

Managing institution

Princeton University

Main scientific focus

HCIL is designed to demonstrate cutting-edge technologies for exoplanet direct imaging and characterization from space-based platforms. The laboratory simulates an integrated telescope and coronagraph instrument, operating in the visible to near-infrared, similar to that baselined for the WFIRST mission. Our specific focus is the development and validation of the shaped pupil coronagraph along with various model-based wavefront control and estimation techniques. On-going developments of the HCIL include the addition of low-order wavefront sensing (LOWFS) and an integral field spectrograph (IFS).

Environment of the testbed

The testbed is located in a 900 sq. ft. clean room with temperature and humidity control. The testbed is equipped with vibration isolation and a clean air system designed for optical research.

Key hardware items

• A star-planet simulator using two fiber sources with different wavelengths is used as the source. An off-axis parabola (OAP) is used to create the collimated beam.
• Two Boston MicroMachine kilo-DMs with 952 active actuators on each are used for wavefront control and estimation.
• The starlight diffraction pattern is modified by a rippled-shaped pupil coronagraph (SPC) and the energy outside of the dark holes is blocked using a bowtie-shaped focal plane mask (FPM).
• A science camera (QSI model RS 6.1s) is placed on a 300mm motorized stage for focal plane imaging and phase retrieval.

Current status

Using the shaped pupil coronagraph only, the testbed can reach a contrast of 1x10^(-4). The addition of the 2 -DM focal plane wavefront control improves the contrast to 1x10^(-7). Several new wavefront control and estimation algorithms, including EFC, stroke minimization, Kalman filtering, and extended Kalman filtering, have been demonstrated in this layout. Current research is directed at achieving end-to-end system identification and reinforcement learning control.

Future Developments: The testbed will be equipped with low-order wavefront sensing based on the reflected light from the FPM in the near future. A lenslet-based integral field spectrograph (IFS) is under development as a demonstration for the WFIRST coronagraph instrument (CGI). It features an 18% band around 660nm with a spectral resolution of 50 and will be used to demonstrate IFS-based closed-loop broadband wavefront control.