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The ANFF is
an open access network comprising of eight Nodes across 21 institutions with
a portfolio of more than 500 tools valued at over $200 million. See: for full details |
Success StoriesDiamond Turned Optical AxiconCaF2 axicons, both concave and convex, were fabricated to form high aspect ratio Bessel beams which were used in experiments for micro explosion generation inside sapphire. The diamond turning machine used for the work is a Moore Nanotech UPL250, ultra-precision lathe. The workpiece, a 5 mm thick 1-inch diameter CaF2 window, was held on the spindle by a vacuum chuck. The cutting process consists of roughing passes and fine finishing passes. For the roughing cut, cut depth was set 20 μm, with feed rate of 7.5 μm/rev using a 0.5 mm radius diamond cutter. For the finishing pass, the cut depth was reduced to 2 μm, with feed rate of 2.5 μm/rev using a 0.6mm radius special edged cutter. After each finishing pass, the surface finish of the lens was monitored by using an on-machine white-light interferometer, to check if the final surface quality meets the requirements. After turning, the axicons were characterised with a Wyko NT9100 surface profiler from Veeco to measure their geometries. The measured profiles were compared to an ideal cone with an apex angle of 179 degrees. Our product was compared with a positive commercial axicon: The commercial axicon was a 25.4 mm 1-degree (apex angle of 179 degrees) AR coated positive axicon made of UV Fused Silica. Figure 1(a) presents the profile, in blue, of this axicon. Clear differences can be observed in the rounded tip tip of the commercial axicon compared to the sharper tip for our homemade axicon. Moreover, it was noticed that the slope of the commercial axicon was not perfectly straight and bumps were observed along it, as it can be observed in the right section of the blue curve profile. Profilometer image of a 3D contour and cross section over the tip of the fabricated (a) positive and (b) negative axicons. Blue profile is the commercial axicon for comparison. In the customer’s micro explosion generation experiment, our products demonstrated superior quality in terms of sharp peak with homogeneous concentric rings. The optical performance of the diamond turned axicon was also measured. Shown below is the measured 1030 nm wavelength Bessel beam with a 1.2 micron diameter central core produced by the axicon which meets the diffraction limited theoretical performance:
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