Achromatic Deep Ultraviolet Lens Using Fluoride Crystals

Abstract

  Deep ultraviolet (DUV) light that span the wavelength range from 200 to 300 nm have numerous scientific and technological applications including spectroscopy, environmental monitoring, surface micromachining, and sterilization. Fluoride crystals have high transparency in DUV region because of their wide bandgap. In this report, we calculated the achromatic aberration of the couples of convex and concave lenses consist of fluoride crystals. Based on the calculated results, the prototype of achromatic objective lens in the wavelength range from 200 to 300 nm is fabricated. The prototype lens of a LiCaAlF₆ and SiO₂ has a focal length of 10 mm, working distance of 2mm, and numerical aperture of 0.2 with a chromatic aberration of about 2.8 %.