Manufacture
GRIN lenses are made by several techniques:
- Neutron irradiation (Sinai, 1971) – Boron-rich glass is bombarded with neutrons to cause a change in the boron concentration, and thus the refractive index of the lens.
- Chemical vapour deposition (Keck et al., 1975) – Involving the deposition of different glass with varying refractive indexes, onto a surface to produce a cumulative refractive change.
- Partial polymerisation (Moore, 1973) – An organic monomer is partially polymerized using ultraviolet light at varying intensities to give a refractive gradient.
- Ion exchange (Hensler, 1975) – Glass is immersed into a liquid melt with lithium ions. As a result of diffusion, sodium ions in the glass are partially exchanged with lithium ones, with a larger amount of exchange occurring at the edge. Thus the sample obtains a gradient material structure and a corresponding gradient of the refractive index.
- Ion Stuffing (Mohr, 1979) – Phase separation of a specific glass causes pores to form, which can later be filled using a variety of salts or concentration of salts to give a varying gradient.
Read more about this topic: Gradient-index Optics
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