Flexible and Red-Emissive Organic Single-Crystal Microresonator for Efficient Active Waveguides

Takumi Matsuo; Junpei Kuwabara; Takaki Kanbara; Shotaro Hayashi

doi:10.1021/acs.jpclett.3c01495

Flexible and Red-Emissive Organic Single-Crystal Microresonator for Efficient Active Waveguides

J Phys Chem Lett. 2023 Jul 27;14(29):6577-6582. doi: 10.1021/acs.jpclett.3c01495. Epub 2023 Jul 17.

Authors

Takumi Matsuo¹, Junpei Kuwabara², Takaki Kanbara², Shotaro Hayashi^{1

3}

Affiliations

¹ School of Science and Engineering, Kochi University of Technology, Kami, Kochi 782-8502, Japan.
² Tsukuba Research Center for Energy Materials Science (TREMS), Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan.
³ Research Center for Molecular Design, Kochi University of Technology, Kami, Kochi 782-8502, Japan.

PMID: 37458725
DOI: 10.1021/acs.jpclett.3c01495

Abstract

We fabricated a flexible and red-emissive microcrystal resonator for highly efficient optical waveguiding. The microfiber crystals of diketopyrrolopyrrole (DPP) used in this work possess a high photoluminescence (PL) quantum efficiency (Φ_PL = 0.45) and exhibit a micromechanical deformation shape in the curved state. The crystals show optical fringes in their PL spectra, suggesting the existence of a naturally formed Fabry-Pérot crystal resonator owing to its flat crystal surface. The group refractive index (n_g) and Rabi splitting energy (ℏΩ) indicating the coupling strength between excitons and resonator photons are large (n_g = 3.7-6.0, ℏΩ = 1.38 eV), suggesting the strong confinement of waveguiding photons. Spatially resolved PL measurements revealed that the PL in a crystal fiber is efficiently waveguided, even in a curved crystal with a very small curvature radius of 11 μm. Strong photon confinement inside a crystal resonator is a plausible origin of efficient optical waveguiding.