NANOPHOTONICS: Near-field polishing yields ultraflat silica surface

摘要

Conventional chemical-mechanical polishing (CMP) methods are typically used to obtain surfaces figured to sub-100-nm tolerances on optical and semiconductor materials for specialized applications. While CMP methods can yield surface roughnesses on fused silica down to approximately 2.36 A, scientists at the Japan Science and Technology Agency (SORST), the University of Tokyo, and Sigma Koki (all in Tokyo, Japan) have developed an optical near-field, nonadiabatic photochemical photodissociation process that can further polish this type of surface to a roughness of only 1.37 A. Photodissociation is the process by which light energy causes reacting molecular gases to resonate in order to excite molecules from the ground state to an excited electronic state. The near-field polishing process uses light at a 532 nm wavelength from a continuous-wave laser in the presence of molecular chlorine (Cl_(2)), which serves as an etching gas; the laser light selectively photo-dissociates the chlorine near surface protrusions on the silica substrate.