Flattening property of a surface due to optical assisted chemical near-field etching

A mechanism of surface flattening is proposed based on our original mathematical model of surface development by introducing a protrusion-selective etching process which has been demonstrated by the optical near-field assisted chemical etching of glass substrate. We study various mechanisms of surface development due to etching processes depending on the local curvature of substrate and explain that the nature of optical near-field showing the stronger field–matter coupling and associated field enhancement near a sharper protrusion is essential for the flattening property.