Mechano-Photonics: Flexible Single-Crystal Organic Waveguides and Circuits.

: Microfabrication of circuits by combining the mechanical and photonic properties of flexible crystals is imperative for flexible miniature photonic devices. The fundamental understanding of molecular packing and energetics of intermolecular interactions is imperative to design such crystals with intrinsic flexibility and optical attributes. We present a rare one-dimensional optical waveguiding crystal of dithieno[3,2-a:2',3'-c]phenazine( 1 ) with high aspect ratio displaying high mechanical flexibility and selective self-absorbance of the blue part of its fluorescence (FL). Though, macrocrystals exhibit elasticity, microcrystals deposited at a glass surface behave incredibly like plastic crystals due to significant surface adherence energy, making them suitable for constructing photonic circuits via micromechanical operation with atomic force microscopy cantilever tip. Phenomenally, the flexible crystalline waveguides display optical path-dependent FL signals at the output termini in both straight and bend configuration suitable for wavelength division multiplexing technologies. A futuristic reconfigurable directional coupler fabricated via micromanipulation by combining two arc-shaped crystals split the optical signal via evanescent coupling and deliver the signals at two output terminals with different split ratios. The presented mechanical micromanipulation technique could also be effectively extended to any flexible crystals to design and carve complex photonic circuits.