High-efficiency anti-reflective modification of freeform elements and cylindrical lenses for arrayed wide-field astronomical corrector units

Abstract

Randomly distributed anti-reflective nanostructures were fabricated on both surfaces of cylindrical lenses and freeform optical elements using a plasma-assisted reactiveion etching technique. An average spectral transmission of 98% was measured across the wavelength range from 340 to 800 nm. Mid-band full-angle directional scatter measurements show a difference of six orders of magnitude in transmission intensity between specular and off-specular angles. Measurements before and after the etching process show little to no wavefront distortion for the cylindrical lenses. The enhanced transmission optics were used as part of the dual-unit arrayed wide-field astronomical camera system tested on the Harlan J. Smith telescope at the McDonald Observatory, and their performance was contrasted with conventional thin film coated component performance.