Optical Waveguides Based on Single‐Crystalline Organic Micro‐Tiles

Abstract

Surface waveguides are an important topic because of their ability to transmit sub-wavelength information, [ 1 ] that is, details with dimensions less than the wavelength of visible light, which holds promise for utilization in faster and more compact optoelectronic communications and sensors. [ 2 ] Great effort has been put into optical waveguides based on onedimensional (1D) inorganic nanostructures. For example, Lieber’s group [ 3 , 4 ] and Yang and coworkers [ 5 , 6 ] have demonstrated that crystalline wireand ribbon-like nanomaterials of inorganic semiconductors can successfully serve as waveguides for light with wavelengths less than that of visible light. Then, Redmond and coworkers reported the waveguiding property of conjugated polymer nanowires. [ 7 ] Very recently, optical waveguides based on 1D structures of small organic molecules have been realized using nanowires, nanoribbons, and nanofi bers. [ 8–14 ] However, optical waveguides based on small organic molecules with 2D structures are still in their infancy. [ 15 ] They are expected to display waveguiding behavior different from that of 1D materials owing to their different microstructures. Furthermore, it should be of great scientifi c interest to extend the relevant research from solid 1D nanorods/wires/ tubes to 2D micro-tiles, because the 2D tile structures are more suitable for the application of controlling directional waveguides. Here, we report the preparation of 2D crystalline microstructures, that is, micro-tiles, from hexaphenylsiloles (HPSs), small organic compounds, by self-assembly. Characterization of single micro-tiles indicates that the 2D HPS microstructures can serve as active optical waveguides that allow locally excited photoluminescence to propagate along the abscissa of the 2D structures and out-couple at the ridge tips. The unique 2D optical waveguiding phenomenon of HPS micro-tiles might be useful