Continuously chirped gratings for DFB-lasers fabricated by direct write electron-beam lithography

The fabrication of DFB (distributed feedback) gratings containing small variations of the grating pitches (chirped gratings) by means of direct write electron-beam lithography is presented. The procedure allows the generation of pitch variations in the pm range, which is required for the realisation of chirped gratings. By use of this technology we are able to realise almost every pitch sequence that can be expressed mathematically. This paper will show the technology of generating chirped gratings by use of a standard electron-beam lithography system. The focus on this technology was not to realise the pitch variations precisely, but rather to give a general fabrication technology for chirped gratings.