Scanning Phase Stepping Interferometry for High Resolution Measurement

The overall goal of this Phase I effort is to design and verify the feasibility of a new Scanning Phase Stepping Interferometer (SPSI) compatible with the Crystal Growth by Vapor Transport (CGVT) materials science experiment proposed to the Microgravity Science & Applications Department at NASA's Marshall Space Flight Center, Alabama. (MSFC). SPSI is capable of resolving crystal terraces on the order of 0.5 nm in height, well below the 5-100 nanometer step height resolution required by this materials science experiment. In this proposal, we describe not only the technique itself, but also some of the optical engineering which must be addressed for implementation. In the Phase I design and testing, feasibility and performance will be the primary goals, while in Phase II, a more compact, flight-compatible prototype will be built taking into account constraints in size, weight, and power on the International Space Station. The proposed SPSI system will incorporate conventional gross field phase stepping capabilities, and will be compatible with optical absorption measurements. In this project, Rice Systems will investigate the application of SPSI to other crystal growth experiments, as well as to microstructure applications where conventional phase stepping does not have sufficient cross-axis resolution.