Impact of Plasmonic and Dielectric Substrates on the Whispering-Gallery Modes in Self-Assembled Fluorescent Semiconductor Polymer Microspheres

Zhan-Hong Lin; Soh Kushida; Fan-Cheng Lin; Jhih-Yuan Chen; Ankit Kumar Singh; Yohei Yamamoto; Jer-Shing Huang

doi:10.1021/acs.nanolett.3c01463

Impact of Plasmonic and Dielectric Substrates on the Whispering-Gallery Modes in Self-Assembled Fluorescent Semiconductor Polymer Microspheres

Nano Lett. 2023 Jul 26;23(14):6512-6519. doi: 10.1021/acs.nanolett.3c01463. Epub 2023 Jul 5.

Authors

Zhan-Hong Lin¹, Soh Kushida², Fan-Cheng Lin³, Jhih-Yuan Chen³, Ankit Kumar Singh¹, Yohei Yamamoto², Jer-Shing Huang^{1

3

4

5

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Affiliations

¹ Leibniz Institute of Photonic Technology, Albert-Einstein Straße 9, 07745 Jena, Germany.
² Department of Materials Science and Tsukuba Research Center for Energy Materials Science (TREMS), Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan.
³ Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
⁴ Research Center for Applied Sciences, Academia Sinica, 128 Sec. 2, Academia Road, Nankang District, 11529 Taipei, Taiwan.
⁵ Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich-Schiller University Jena, 07743 Jena, Germany.
⁶ Department of Electrophysics, National Yang Ming Chiao Tung University, 1001 University Road, 30010 Hsinchu, Taiwan.

PMID: 37405910
DOI: 10.1021/acs.nanolett.3c01463

Abstract

In this work, the impact of metallic and dielectric conducting substrates, gold and indium tin oxide (ITO)-coated glass, on the whispering gallery modes (WGMs) of semiconductor π-conjugated polymer microspheres is investigated. Hyperspectral mapping was performed to obtain the excitation-position-dependent emission spectra of the microspheres. Substrate-dependent quenching of WGMs sensitive to mode polarization was observed and explained. On a glass substrate, both transverse-electric (TE) and transverse-magnetic (TM) WGMs are quenched due to frustrated total internal reflection. On a gold substrate, however, only the TM WGMs are allowed in symmetry to leak into surface plasmons. An atomically flat gold substrate with subwavelength slits was used to experimentally verify the leakage of WGMs into the surface plasmon polaritons (SPPs). This work provides insight into the damping mechanisms of WGMs in microspheres on metallic and dielectric substrates.

Keywords: Otto configuration; fluorescent π-conjugated polymer microspheres; frustrated total internal reflection; surface plasmon resonance; whispering gallery modes.