Fabrication of continuous phase plates with small structures based on recursive frequency filtered ion beam figuring

Abstract

Large surface gradient and extensive mid-to-high spatial frequency in continuous phase plates (CPPs) with small structures make it difficult to achieve high-precision fabrication. An ion beam figuring (IBF) technology to fabricate CPPs with such characteristics is proposed in this paper. In order to imprint CPP microstructures with smaller spatial periods even down to 1mm in shorter time, we present a multi-pass IBF approach with different ion beam sizes based on the frequency filtering method. We discuss the selection principle and when to reduce ion beam sizes for different procedures to control dwell time and adequately exert the corrective capability in detail. This filtering method can obtains better surface quality in a faster way compared to the non filtering traditional IBF method. The experimental results verify this optimized method can effectively imprint complex microstructures with spatial period as small as 0.7 mm, surface peak-to-valleys (PV) smaller than 200nm and surface gradient as large as 1.8μm/cm to within 10 nm root-mean-square (RMS) of design specifications, which displays the advantages of our fabrication method.

Continuous Phase Plate Structuring by Multi-Aperture Atmospheric Pressure Plasma Processing

“…Ion beam figuring (IBF) has the potential to figure structures down to 1 mm and different sizes of removal spots can be achieved with a shielding diaphragm. However, the low removal rate limits its application to large and steep CPPs [6].…”

Surface Texture Evolution of Fused Silica in a Combined Process of Atmospheric Pressure Plasma Processing and Bonnet Polishing

“…This process does not suffer misfit issues on aspheres and freeforms [8], but the absence of a pad renders it unsuitable for pre-polishing a rough surface: it is a finishing process, as the name implies. For ultra-precision finishing, ion beam figuring (IBF) provides nanometer-scale material removal [9,10], but again, without polishing capability. In addition, the shear-thickening polishing (STP) [11,12], elastic emission machine (EEM) [13] and fluid jet polishing (FJP) [14] also draw much research attention.…”