Assessment of a photosensitive sol-gel as a space ready material through the recording of Holographic Optical Elements

Wavefront sensors (WFS) are a vital piece of the many instruments allowing for accurate imaging of the night sky, optical communications and medical imaging. Holographic wavefront sensors (HWFS) have been shown over the years to be a new branch of WFS for adaptive optics. With the application of Space in mind, performance is not the only factor we have to consider. With thousands of satellites and CubeSats being launched into orbit each year, the weight and sturdiness of the payload are crucial. This paper looks at the potential of photosensitive sol-gel material to replace the more standard photopolymers used in holography. This is done by recording several holographic lenses in the sol-gel and using Bragg curves, analysing levels of shrinkage and'dark processes' within the hologram and its diffraction efficiency over extended periods of time. The reduction in weight and the inexpensive production could pave a new way for developing highly accurate, lightweight and cheap Holographic Wavefront Sensor (HWFS) for furthering space exploration as well as applications here on Earth. The study was able to show the significant impacts shrinkage and dark processes have on the holograms diffraction efficiency and spatial frequency distribution over a significantly short period of time, within 45 minutes. The paper also investigated a possible solution by bleaching the sol-gel post-recording to prevent or minimise these effects. The project proved to be a significant advancement in knowledge in a relatively unstudied material for an extremely versatile application.