Miniaturized Photonic Circuit Components Constructed from Organic Dye Nanofiber Waveguides

Abstract

Self-assembled nanofibers of organic dye thiacyanine (TC) with lengths of up to \( {\sim} 250\,\upmu {\text{m}} \) function as efficient active waveguides that propagate fluorescence (FL) over their entire lengths along the fiber axis. A spectroscopic investigation of the active waveguiding properties revealed that the FL strongly couples with molecular excitons and propagates in the form of exciton-polaritons. Such long-range propagation of exciton-polaritons at room temperature is rarely observed in inorganic materials. The high stability of the exciton-polaritons in the organic dye nanofibers is attributed to the large longitudinal transverse exciton splitting energy and exciton binding energy with respect to thermal energy. Unlike light propagating in conventional waveguides, exciton-polaritons can pass through bends in nanofibers with micron-scale radii of curvature. Utilizing this property, we fabricated miniaturized photonic circuit components using nanofiber building blocks. The fabricated components, including Mach–Zehnder interferometers and microring resonators, exhibit considerably high performance for their micron-scale dimensions. In addition to such photonic device applications, the organic dye nanofibers are ideal systems for studying the physics underlying strong light–matter interactions. In particular, the highly stable nature of the exciton-polaritons at relatively high temperature offers the possibility of a representative novel quantum phenomenon in their Bose–Einstein condensation (BEC). A theoretical analysis of this exciton-polariton BEC in the nanofiber system is presented in this chapter.