Advanced matrix laser lithography for fabrication of photonic micro-structures

Direct laser beam writing techniques represent an interesting alternative to focused electron and ion beam writing approaches for the fabrication of photonic micro-structures. Although the resolution of laser beam writers is strongly limited by the Rayleigh diffraction limit, it is not always necessary to create features significantly smaller than the recording wavelength. In such cases, a laser exposure can be used, with all its advantages. In this paper a direct laser writing technique is presented one; which significantly improves the performance of commonly used direct laser writers by introducing an exposure of a large area within a single step. The elementary exposed area can contain a general micro-structure without any special requirements. In contrast to writing techniques based on a single spot focus, the writing beam can have the shape of a general aperiodic structure and exposes an area of about 10^-2 square millimetre. This complicated exposure field is created using a demagnified projection of the exposed structure from a two-dimensional computer-driven spatial light modulator. The main advantages of the method compares to the single point exposure are a significantly improved exposure speed, a perfect alignment of features within a single exposed area, and the possibility of tuning the exposing field very precisely using continuous modulation of the signal on the spatial light modulator. The in-house-developed device is presented together with several realized samples