Selective liquid filling of photonic crystal fibers using two-photon polymerization lithography without post-exposure development

Selective liquid filling of photonic crystal fibers opens up possibilities for tailoring their guidance properties or adding new functionalities. Among other techniques, 3D printing on optical fiber tips using two-photon polymerization has been applied for selective infiltration of individual air holes in photonic crystal fibers with liquids. However, in existing techniques care should be taken during the post-print photoresist development in order to avoid penetration of the developer solution into the air channels intended for filling. This limits the applicability of those methods. The technique proposed in this paper ensures that contamination of the air holes with the developer solvent is prevented. We apply two-photon polymerization lithography followed by an injection-cure-cleave procedure while omitting the post-exposure development. Selective filling of two fiber types is demonstrated. The first is a birefringent fiber with two rows of 3.6 mu m air holes and one row of 0.9 um holes in between. Another PCF has a hexagonal arrangement of 1.4 mu m air holes. Our approach allows repeated selective filling to realize the infiltration of more than one liquid. Optofluidic fiber devices filled with one or more liquids have potential applications in the nonlinear optical domain and in the field of fiber sensing.