Microfabrication of microlens array by focused ion beam technology

Microfabrication process of piano-convex microlens arrays with continuous r elief for refractive and diffractive usage by focused ion beam (FIB) techno logy is introduced in detail in this paper. Two functions of FIB - milling and deposition of SiO2 are used for the fabrication. A 9 x 9 micro-diffract ive optical elements (DOEs) array with singlet f-number of 2 and NA value o f 0.25, and a 9 X 9 refractive microlens array with singlet diameter of 60 mum, NA value of 0.1, and f-number of 5 are designed and fabricated by the milling method. In addition, the other method of FIB induced SiO2 depositio n for microlens is introduced. The lens profile and focusing characteristic s are measured by WYKO NT2000 interferometer and BeamScope-5 PTM beam scann er respectively. Focused spot size is about 6.7 mum (at site of 50%) and 5. 1 mum (at site of 1/e(2): 13.5%) for diffractive lens and refractive lens a rray respectively. The RMS thickness error within a diameter of 27 mum DOEs and 60 mum of refractive lens (by the way of milling) is 11 nm, and 15 nm respectively. Wave aberration for both of them are 1.7 wave and 1.5 wave re spectively. (C) 2000 Elsevier Science B.V. All rights reserved.