Calibration of etching uniformity for large aperture multilevel diffractive optical element by ion beam etching

Abstract

Ion beam milling is a suitable technique for manufacturing optical elements. It has the advantages of accurately controlling and maintaining a constant optical index. However, it is very difficult to ensure etching uniformity on large areas due to the instability of the machine during sputtering. In this article, the etching speed is analyzed, and selection criteria of corresponding technological parameters are proposed. An available calibration method is put forth to improve etching depth uniformity. Etching is divided into several steps and the sample is rotated to change its position on the target after each step. It is proved by experiment that this is very practical for actual fabrication with a 5%-15% improvement of depth uniformity from previous results.

Miniaturization of optical spectroscopes into Fresnel microspectrometers

“…2, tiny Fresnel circular gratings (zone plates), with diameters of 750 μm, were fabricated using a gallium focused ion beam (FIB) machine, the Helios system from FEIBeam technology Co. [31][32][33][34][35] A quartz disc was cleaned with acetone, isopropanol, and deionized water. A thin film of gold was deposited to the thickness of 0.4 μm from a tungsten boat using a thermal evaporator.…”

Fabrication by Reaction–Diffusion: Curvilinear Microstructures for Optics and Fluidics

“…15 This coupling between reaction products and gel dimensions/topography is central to translating RD controllably into the shapes of the objects we wish to fabricate. Here, as the reaction (precipitation) front propagates, the unreacted Fe(CN) 6 4À experiences a sharp concentration gradient at this front and diffuses in its direction -that is, radially outward (þ r direction, red arrows in Figure 6.2(b)). When the surface of the stamp comes into conformal contact with gelatin, water and ions diffuse from the stamp into the dry gel ( Figure 6.2(b) and Example 6.1).…”

“…Our microfabrication process begins by placing a WETS stamp soaked in a solution of AgNO 3 and micropatterned in bas relief with an array of cylindrical depressions ('wells') onto a thin film of dry gelatin uniformly loaded with K 4 Fe (CN) 6 (Figure 6.2(a)). This 'outflow'decreases the concentration of [Fe(CN) 6 ] 4À anions near the circles centers so that by the time Ag þ cations diffuse therein, they find fewer precipitation 'partners' than they had near the patterned edges. In doing so, the silver cations -constantly resupplied from the stamp -precipitate all hexacyanoferrate anions they encounter and cause the gel to swell.…”

“…When this stamp is applied onto a thin layer of dry gelatin, doped with another chemical B (e.g., K 4 Fe(CN) 6 ), water and A are transported into the gel, where A and B react to form an insoluble product. When this stamp is applied onto a thin layer of dry gelatin, doped with another chemical B (e.g., K 4 Fe(CN) 6 ), water and A are transported into the gel, where A and B react to form an insoluble product.…”

“…Trends based on experimental surface profilograms ( Figure 6 6 ] (up to 1% w/w; above this concentration, the gelatin does not gelate properly and tends to 'melt' upon stamping). Since local deformations of the gel surface depend on the underlying concentrations of the precipitate, the shapes of the developed lenses can be controlled by the concentrations of the salts used and/or the dimensions of the stamped features.…”