Realization of refractive continuous phase elements with high design freedom by mask structured ion exchange

We suggest a new technique for fabricating a wide class of continuous refractive optical elements in glass by combining the technique of ion exchange with high precision structuring of metal masks. We call this technique mask structured ion exchange (MSI). We have demonstrated the potential of this method by fabrication of rectangular shaped microlenses with low numerical aperture for Hartmann-Shack wavefront sensing applications. The lenses, positioned on a 400 µm raster, had a fill factor of 100 %, a focal length of 33 mm and diffraction limited performance. Due to the special fabrication conditions, the lens shape, position and even the focal length can be varied spatially within one substrate. For realization of a high aperture microlens array by field assisted exchange process we could reduce proximity effects between adjacent mask apertures by MSI