Ultrafast laser welding of x-ray mirror segment stacks

Designing and building X-ray telescopes that observe the high-energy universe with large-effective area and sub-arcsecond angular resolution has proven to be a great optomechanical challenge, as thin, tightly nested grazing-incidence mirrors are easily deformed during assembly. We are developing a bonding and alignment process in which we fabricate spacers, bond them between thin mirrors, and re-align these mirrors after assembly, using a Hartmann test for alignment metrology. We implemented a non-contact slumping method to produce smooth Corning Eagle XG conical mirrors. Using an ultrafast laser, we welded fused silica spacers to flat fused silica mirrors to create mirror segment stacks. We performed a parameter study on ultrafast laser welding Eagle XG to fused silica, which we expect to enable building an X-ray mirror segment stack with our slumped Eagle XG mirrors and fused silica spacers.