A digital holographic microscope for high-resolution characterization of metasurface optics in the short-wave infrared

There exists a family of optical components used in high-contrast imaging that are essential to achieving performance goals, yet are challenging to fabricate and characterize. This is due to the spatial scales involved, and the requisite manufacturing control needed in this microscopic domain. These elements can be broadly characterized as focal plane masks because they work on the the diffraction-limited focal plane electric field. They include such devices as occulting disks for the classic Lyot coronagraphs, vector-vortex liquid crystal masks, scalar metasurface vortex masks, and Zernike phase-contrast masks (both scalar and vector). Designing, fabricating, and characterizing these focal plane masks at fine spatial scales is an essential and necessary part of closing the loop around the design and development process. Here we present the use of a digital holographic microscope (DHM) that is tailored to the testing and characterization of these masks. We illustrate the operation of this new DHM instrument with data from a couple of different metasurface devices - one scalar and one vector - to showcase the application and utility of the device.