Fabrication of Fused Silica Surfaces with Controllable RMS Roughness and Correlation Length

A fabrication technique is described for producing fused silica surfaces with controllable rms roughness and correlation length. The rough surfaces are generated by coating a fused silica surface with Shipley 1400-17 photoresist and exposing the photoresist to a laser speckle pattern and a coherent reference beam. The photoresist is developed and the structured photoresist surface is eroded into the fused silica surface with an argon ion mill. The rms roughness of the resulting surface is controlled by the exposure energy and development conditions. The correlation function of the surface is related to the Fourier transform of the intensity distribution that produces the speckle pattern. The surface height distribution is a function of the ratio of the reference beam irradiance to the speckle beam irradiance.