NIRCam coronagraphic Lyot stop: design, fabrication, and testing

The NIRCam instrument on the James Webb Space Telescope (JWST) will provide a coronagraphic imaging capability to search for extrasolar planets in the 2 - 5 microns wavelength range. This capability is realized by a set of Lyot pupil stops with patterns matching the occulting mask located in the JWST intermediate focal plane in the NIRCam optical system. The complex patterns with transparent apertures are made by photolithographic process using a metal coating in the opaque region. The optical density needs to be high for the opaque region, and transmission needs to be high at the aperture. In addition, the Lyot stop needs to operate under cryogenic conditions. We will report on the Lyot stop design, fabrication and testing in this paper.