Development of a laser holographic interference lithography system

Fabrication of periodic grating is very important for photonic devices such as Distributed Feedback (DFB) lasers, optical fiber Bragg grating based devices and optical couplers. Here, we report the development of holographic grating techniques utilizing a rotary mirror holder for grating period from 10 μm to 0.5 μm and Fresnel bimirrors for period greater than 1 μm. These holographic technique offers a wide range of tunability, good resolution, relatively simple apparatus, high uniformity and large-coverage of pattern area. A single line HeCd laser was used in these set ups. The grating patterns have been successfully transferred onto GaAs substrate after dry etching with photoresist as mask. In addition, with the insertion of orthogonal Fresnel bimirror in the systems, square grating patterns have been successfully obtained with grating period of 2 μm x 2 μm.