Ultra-precision cutting of linear micro-groove array for distributed feedback laser devices

The tunable range and beam linewidth of distributed feedback laser were determined by fabrication quality of the periodic linear micro-groove array on substrate, which grooves are high sloped and ranged sub-micron to few microns. Compared with the common micro-groove arrays (size from tens of microns to sub-millimetre), the ultra-precision cutting of these tiny and high-sloped linear micro-groove arrays are more difficult to realise. In this paper, a series of investigations was proposed for ultra-precision cutting of linear micro-groove array on polymethyl methacrylate (PMMA). Firstly, the different cutting processes included planing and fly-cutting were conducted. The workpiece morphology, surface quality and machining efficiency of these processes were investigated. Then, the fly cutting process was optimised by the calculation of non-free chip zone and the analysis of chip interference by cutting experiments. Finally, a novel tool positioning method based on acoustic emission was presented in order to realise high accuracy control of micro-groove arrays dimensions.