Assembly and alignment of thin mirrors using ultrafast laser generated strain toward future X-ray telescope optics

Abstract

High-resolution and large-effective-area X-ray telescopes are critical tools for observing the high-energy universe, but the existing quasi-kinematic and over-constrained mounts for aligning mirrors trade off accuracy and strength. We propose a method to fabricate spacers and bond them between thin mirrors, then adjust mirror alignment by focusing ultrafast laser pulses into these spacers. We built a simple mirror stack assembly composed of two flat mirrors bonded to two spacers and wrote laser-induced modifications into these spacers. We interferometrically measured the air gap between the two mirrors after each set of laser-induced modifications. The resulting deformation in the spacers and measured tilt between flat mirrors shows that realignment can be controlled using the ultrafast laser, however there is uncertainty introduced by imperfect mirror stack assemblies. Future work will aim to achieve predictable laser-induced strain. The presented assembly procedure and laser-strain generation process serves as a potential solution to the optomechanically-limited design of current-generation X-ray telescopes. © 2023 SPIE.