Image of the Week - 03 March 2009

Gold-surfaced mirrors are commonly used in mid-infrared (mid-IR) imaging systems due to their reflectivity and lack of chromatic aberration. This is doubly important because there is a small market for mid-IR lenses, which must be made of ionic salts to be transparent in the imaging range of 700-4000 cm-1. One of our current projects involved the creation of a contact-method probe with a fiber optic-based beam guidance geometry coupled to a total internal reflection sensing element, and very small mirrors were required. The smallest available commercial mirrors were 14.5 x 3.5 x 2 mm, whereas our project required dimensions of 1.8 x 1.8 x 1 mm, necessitating custom fabrication. A diamond turn cutter in the Materials Research Laboratory was used to cut squares of the required dimensions from a 1-mm-thick glass slide, and the dual-metal evaporator in the Microscopy Suite was used to deposit 1.2 nm of Cr, followed by 50.7 nm of Au, onto the squares. Two of the resulting mirrors are shown, mounted on double-stick carbon tape. Digital photograph for inspection acquired in the Visualization Laboratory using the macro-photography system.