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▼ [24a-E307-8] Tunable Fabry–Pérot Resonators based on Flexible Organic Microcrystals
Keywords:flexible organic microcrystal, microresonators, waveguide
Mechanically flexible organic crystals (FOCs), which can elastically/plastically bend upon applying external force, represent a unique and emergent materials group in the field of optics because they can transmit light along its longitudinal direction via total internal reflection at the bent state as well as the straight state and, thus, work as flexible optical waveguides. Along this line, optical resonators made of FOCs are also sought after as a future wavelength- and direction-tunable laser emitter. However, synthesis of such FOC resonators remains a fundamental challenge so far because of the inherent optical loss during the light propagation along the longitudinal direction and the reflection at the end facets.
Here, we report a FOC that works as an optical resonator, whose resonance wavelength is finely tunable by mechanical bending. The rod-shape single-crystalline micrograins are synthesized by sluggish precipitation of a fluorescent π-conjugated molecule, cyano-substituted oligo(phenylene-vinylene)s (COPV). In contrast to the existing flexible organic crystalline waveguides that confine light along their longitudinal direction, this crystal (FOCCOPV) confines light along its lateral direction. This cross-sectional optical resonance is kept intact even upon bending up to 90° with a radius of curvature r of 640 μm. Meanwhile, the resonance frequency is monotonically blue-shifted in a wavelength range of ~4 nm due to the geometrical contraction along the lateral direction by the Poisson effect. The mechanically robust and optically tunable organic crystal resonator demonstrated herein will surely contribute to the improvement of the mechanical robustness and optical functionality of organic crystalline optical devices and will lead to the further development and application of FOCs in the field of optics.
Here, we report a FOC that works as an optical resonator, whose resonance wavelength is finely tunable by mechanical bending. The rod-shape single-crystalline micrograins are synthesized by sluggish precipitation of a fluorescent π-conjugated molecule, cyano-substituted oligo(phenylene-vinylene)s (COPV). In contrast to the existing flexible organic crystalline waveguides that confine light along their longitudinal direction, this crystal (FOCCOPV) confines light along its lateral direction. This cross-sectional optical resonance is kept intact even upon bending up to 90° with a radius of curvature r of 640 μm. Meanwhile, the resonance frequency is monotonically blue-shifted in a wavelength range of ~4 nm due to the geometrical contraction along the lateral direction by the Poisson effect. The mechanically robust and optically tunable organic crystal resonator demonstrated herein will surely contribute to the improvement of the mechanical robustness and optical functionality of organic crystalline optical devices and will lead to the further development and application of FOCs in the field of optics.