Fabrication of a DFB Laser in SU-8 by direct femtosecond laser writing

Organic solid-state lasers are promising candidates for inexpensive, small-scale light emitting devices for integration in lab-on-a-chip systems [1]. Among them, dye-doped polymers exhibit a broad gain spectrum providing scope for developing tuneable lasers. Distributed feedback (DFB) structures incorporating a grating structure in the gain medium for selective feedback [2] are particularly interesting for this approach. However, previously demonstrated fabrication techniques as e.g. holographic exposure [2], UV-lithography [3], and nano-imprinting [4] are restricted to planar geometries. In contrast, femtosecond point-by-point fabrication [5] enables DFB laser design with an almost arbitrary topography, permitting the fabrication as e.g. gratings with a nonlinear pitch, and allowing for complex three-dimensional surface corrugations.