Design aspects for the fabrication of gratings for DFB-lasers by direct write electron-beam lithography

The fabrication of gratings for DFB-lasers by direct write electron-beam lithography under consideration of design rule aspects is presented. The mostly common targeted duty cycle value of 0.5 can be achieved by either exposing a designed equal line/space ratio of 0.5 or a smaller ratio implying the necessity to raise the exposure dose in order to obtain equal lines and spaces in the developed resist pattern. We found that the latter way results in an increase in process tolerance without loosing device characteristics.