Opto-mechanical design of a High Contrast Module (HCM) for HARMONI

HARMONI is a first-light visible and near-IR integral field spectrograph of ESO's Extremely Large Telescope (ELT) which will sit on top of Cerro Armazones, Chile. A Single Conjugate Adaptive Optics (SCAO) sub-system will provide diffraction-limited spectral images in a Nyquist-sampled 0.61 x 0.86 arcsec field of view, with a R=3000-20000 spectral resolution. Inside the instrument, a High Contrast Module (HCM) will add an essential high-contrast imaging capability for HARMONI to spectrally characterize young giant exoplanets and disks with flux ratio down to 1e-6 at 0.1-0.2" from their star. The HCM uses an apodized pupil coronagraph to lower the intensity of the diffracted starlight and limit the dynamic range on the detector, and an internal wavefront sensor to calibrate non-common path aberrations. This communication first summarizes the basic technical requirements of the HCM, then describes its optical and mechanical designs, and presents expected performance in terms of achievable contrast, image quality and throughput. Elements of the development and test program are also given.