Small Subsurface Damage Measurement of Optical Materials

Jing (Jane) Xu, Advised by Professor John Lambropoulos

Tuesday, March 22, 2022
2 p.m.

Hopeman 224

Ultraprecision sub-aperture processing methods like magnetorheological finishing (MRF) and ultrafast laser processing allow freeform optics to be manufactured and therefore enable more compact and high-performance imaging systems. Subsurface damage (SSD) affects quality of sub-aperture processed surfaces. The proposed project is aimed at developing a methodology to measure small (sub-micron-level) subsurface damage efficiently and precisely on both symmetric and freeform surfaces. The developed method will be based on tapering methods integrated with MRF and UltraForm Finishing (UFF) spots to expose damaged material. It will also employ mechanical testing techniques together with surface characteristic measurements to track changes of physical properties and mechanical behaviors within damaged zone. This method will be able to reveal any SSD associated with not only surface roughness, but also mid spatial frequency (MSF) errors which have been of high concern for freeform optics. Results of the measurement will be used to help evaluate and compare outcomes of ultrafast laser processing and MRF finishing.