Anomalous optical resonance on supramolecularly chiral metaspheres with a swirl topology

doi:10.21203/rs.3.rs-3594666/v1

Download PDF

Article

Anomalous optical resonance on supramolecularly chiral metaspheres with a swirl topology

https://doi.org/10.21203/rs.3.rs-3594666/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted

You are reading this latest preprint version

The optics of topological structures have progressed, with the expectation of unprecedented spatiotemporal control of light. Micrometre-scale spheres with a mesoscopic molecular order, as represented by liquid crystalline (LC) droplets, occupy a unique position owing to the prominent appearance of a nontrivial topological surface. However, because of the lack of material rigidity, comprehensive studies on the optical impacts arising from topological spherical textures have not yet been achieved. Here, we show mechanically and optically robust chiral polymer microspheres with mesoscopic supramolecular swirl textures that display anomalous optical resonance behaviours. Spatially resolved hyperspectral camera imaging reveals that the whispering gallery modes (WGMs) on the metasphere surface are azimuthally anisotropic and localize along a diagonal path in an asymmetric manner. Reconstructed polarized fluorescence microscope images clearly visualize the swirl arrangement of polymers at the surface, which explains the azimuthally selective WGMs and their wavelength dependency. These findings expand two-dimensional metasurface studies to quasi-three-dimensional non-Euclidean planes and open up the possibility of anisotropic control of light and directional radiation of WGM lasers.

Physical sciences/Materials science/Materials for optics/Metamaterials

Physical sciences/Chemistry/Polymer chemistry/Conjugated polymers

Physical sciences/Materials science/Soft materials/Polymers

Physical sciences/Optics and photonics/Lasers, LEDs and light sources/Organic LEDs

Nanophotonics and microphotonics are rapidly advancing due to the demand for miniaturization of optical devices.^1–3 Microcavities are one of the essential dielectric components capable of trapping and amplifying photons.^4,5 Among various microcavities, dielectric microspheres act as effective cavities for optical resonators and lasers based on whispering gallery modes (WGMs).^6,7 In a spherical microcavity, WGM resonance arises from circular propagation of light along the circumference via total internal reflection (TIR), ensuring high quality factors (Q-factors) and low-threshold lasing.⁸ Since the discovery of silica microbeads that work as optical resonators, various dielectric organic materials have been adopted for WGM resonators, such as dye-doped polymer microspheres, fluorescent conjugated polymer microspheres,^9–13 liquid crystalline (LC) droplets,^14–16 and liquid droplets (Fig. 1, left).^17–19

In contrast to typical WGM resonators with isotropic surfaces, LC droplets feature morphologically isotropic but optically anisotropic surfaces with topologically nontrivial molecular order. Typical optically anisotropic LC droplets include bipolar and twisted-bipolar (TB) configurations, where LC molecules are planarly anchored on the spherical surface with two topological defects at opposite poles (Fig. 1, right).^20–22 The pair of topological defects are inherent and stable according to Poincaré-Hopf and Hairy Ball theorems, with a total topological charge of two on the spherical surface.^23–25 Regarding these topological features, bipolar microspheres are outstanding objects for exploring how the topology on the spherical surface affects circulating light. However, despite various reports on LC droplet-based WGM resonators, studies on the correlation between the topological structure and optical confinement have rarely been discussed, possibly due to the difficulty in handling fluidic LC droplets.

Regarding this issue, we recently reported that fluorescent chiral π-conjugated polymers form supramolecular microspheres with a TB configuration.²⁶ In contrast to LC droplets, the TB microspheres feature mechanical robustness, allowing us to demonstrate angularly anisotropic circularly polarized luminescence arising from the anisotropic helical-cholesteric internal structure. Owing to its highly spherical morphology and luminescence properties, the TB microsphere has the potential to act as a fluorescent WGM resonator. In this context, the self-assembled TB microsphere has an advantage in probing distinctive light-matter interactions through the resonant light circulating on the twisted topological surface. Because WGMs are circularly confined modes at the sphere surface, they are highly sensitive to the surface molecular arrangement.³⁵

In this article, we demonstrate distinct impacts on WGM resonance arising from topological textures formed on a spherical microcavity. Mechanically and optically robust microspheres with a TB topology are prepared by a self-assembly process in solution. Upon focused laser excitation, the microspheres exhibit WGM photoluminescence (PL) and lasing. Hyperspectral camera (HSC) imaging shows that the TB microsphere displays anomalous WGMs with azimuthally directional trajectory at diametrically opposite positions, which is in clear contrast with the circularly symmetric (normal) HSC images from amorphous microspheres. Reconstructed polarized fluorescence (FL) microscopy images visualize the swirl arrangement of the polymers at the surface of the TB sphere, which clearly explains the azimuthally selective WGM PL and its wavelength dependency. We envision that the present metaspheres could be applicable to novel optical technology that enables light to be manipulated in a three-dimensional manner at the micrometre scale.

The chiral conjugated polymer (S,S)-PFBT was synthesized according to the reported procedure (Fig. 2a).²⁷ PFBT is a donor-acceptor alternating copolymer that displays a yellowish-green PL colour (Supplementary Fig. 1).^{28, 29} TB microspheres of (S,S)-PFBT ((S)-TB-MS) were prepared by a vapour diffusion (VD) method (Supplementary Fig. 2; for details, see Methods).²⁶ Scanning electron microscopy (SEM) images of the resultant precipitates show a well-defined spherical morphology with a diameter (d) ranging from 1.5 to 4.5 µm (Fig. 2b). The characteristic angle-dependent polarized optical microscopy (POM) texture is assigned as the TB configuration of (S,S)-PFBT in the microsphere (Fig. 2c, d and Supplementary Fig. 3).²⁶ As the enantiomeric counterpart, TB microspheres of (R,R)-PFBT ((R)-TB-MS) were synthesized in a similar way (Supplementary Fig. 4). For comparison, amorphous microspheres of achiral PFBT (a-PFBT) were prepared by a miniemulsion (ME) method (Fig. 2f and Supplementary Fig. 5; for details, see the Methods).³⁰ The ME method under kinetic control results in the formation of well-defined amorphous microspheres (a-MS) without obvious birefringence in the POM image (Fig. 2g–i).³¹

The PL spectra of a single microsphere were measured by means of the microscopic PL (µ-PL) technique under ambient conditions (Supplementary Fig. 6; for details, see Methods). Upon focused continuous-wave (CW) laser irradiation (λ_ex = 450 nm) at the perimeter of a microsphere on a quartz substrate, both (S)-TB-MS (d = 3.2 µm) and a-MS (d = 2.8 µm) exhibit periodic PL peaks, overlapping the broad PL band (Fig. 2e, j). These characteristic PL peaks are attributed to WGMs, where the PL generated inside the sphere is confined via TIR at the polymer/air interface. PL spectra for different values of d are shown in Supplementary Fig. 7a, b. The PL peaks from a-MS are assigned as transverse electric (TE) and transverse magnetic (TM) modes (Supplementary Fig. 7c) using equations S1 and S2 in the Supplementary Information.

Regarding the spectral shapes, the series of WGM PL peaks from (S)-TB-MS is remarkably broader than that from a-MS. We evaluated the full width at half maximum (FWHM) of the WGMs based on the linewidth of the resonance peaks (Supplementary Fig. 8a). The average FWHM (FWHM_av) values of (S)-TB-MS and a-MS are 4.9 and 1.7 nm, respectively, for microspheres with d values of 2.5–4.5 µm (Supplementary Fig. 8b). These results indicate that despite the virtually analogous surface smoothness and sphericity, the resonance mode of (S)-TB-MS appears to be less pronounced than that of a-MS (vide infra). Likewise, upon femtosecond (fs) pulse pumping of a single microsphere (λ_ex = 397 nm, pulse duration = 300 fs, and repetition = 1 kHz; see Supplementary Fig. 9 and Methods), both a (S)-TB-MS and a-MS display lasing behaviour above the pumping threshold (P_th), while the average P_th of a-MS (30 µJ cm^–2) is 5 times smaller than that of (S)-TB-MS (150 µJ cm^–2, Supplementary Fig. 10). The higher P_th of (S)-TB-MS than a-MS is consistent with the FWHM_av results, further supporting the less pronounced resonance property of (S)-TB-MS compared with a-MS.

To visualize the resonance behaviour on the cavity surface, HSC imaging was performed for (S)-TB-MS and a-MS (Fig. 3a). As shown in Fig. 2c and Supplementary Fig. 3, (S)-TB-MS shows an angle-dependent POM texture, whose relationship with the angle (θ) of the bipolar axis with respect to the substrate normal was previously identified.²⁶ Considering the POM texture information, (S)-TB-MS (d = 4.4 µm) was mounted on a substrate with θ = 90° (bipolar axis parallel to the substrate) by means of micromanipulation equipment (Fig. 3b, c and Supplementary Video 1). Upon photoexcitation (λ_ex = 400–440 nm), spatially and spectrally resolved PL images were collected from the entire (S)-TB-MS (Fig. 3f). The PL spectrum obtained from the entire microsphere shows rather broad WGM resonant peaks (Fig. 3d (i) and f (i)).

The λ_em-dependent FL images of (S)-TB-MS show that the resonant PL is particularly emitted from diametrically opposite spots in the first and third quadrants (Q1 and Q3, respectively, Fig. 3d (ii) and f (ii: green box)) as well as near the poles (Fig. 3d (iii) and f (iii: orange box); for details, see Supplementary Fig. 11 and Supplementary Video 2). Intriguingly, the luminous spots in Q1 and Q3 obviously shift in the counterclockwise direction along the circumference from φ = 18 to 45° (Fig. 3e) as λ_em increases for each resonant peak. In addition, rather broad spots at the poles split around the bipolar axis (Supplementary Fig. 12). The continuous movement of the WGM PL spots with increasing λ_em indicates that the characteristic broad resonant peak of the TB microsphere results from the overlap of the λ_em-dependent resonant peaks (vide ante). Azimuthally selective WGM PL behaviour is not observed when (S)-TB-MS is set on the substrate with θ = 0°, in which uniform emission from the circumference of (S)-TB-MS is observed (Supplementary Fig. 13 and Supplementary Video 3). Similar uniform emission behaviour is observed for the amorphous a-MS (Supplementary Fig. 14 and Supplementary Video 4).

The θ-dependent WGM resonance from (S)-TB-MS is consistent with its axially symmetric structure, not the radially symmetric structure (Fig. 1). When (S)-TB-MS is set at θ = 90°, at which the TB axis is parallel to the substrate, the focal plane includes the meridional circumference of the microsphere, whose cross-section features the azimuthally ordered cholesteric helical axis of PFBT (Supplementary Fig. 15a). Accordingly, the diametrically opposite WGM resonances are plausibly associated with the azimuthally varying supramolecular order of PFBT on the surface. However, the observed asymmetric WGM emission cannot be simply explained by the cross-sectional structure, and the details are discussed in the next section. Meanwhile, at θ = 0°, the focal plane includes the equatorial circumference of the microsphere, at which the cholesteric order is radially arranged from the core to the rim (Supplementary Fig. 15b).

To gain insight into the asymmetric WGM resonant spots shown in Fig. 3, the arrangement of the PFBT main chain on the surface of (S)-TB-MS was studied by means of polarized FL imaging, schematically shown in Fig. 4a. Figure 4b shows a plot of the FL intensity collected at the centre of (S)-TB-MS with θ = 90° versus the rotation angle of the analyser (φ_A) upon nonpolarized light excitation (λ_ex = 400–440 nm). The plot shows a clear φ_A dependency: The FL intensity has a maximum and a minimum at φ_A = 140° and 50°, respectively, at which the direction of the analyser coincides well with the directions parallel and perpendicular to the electronic transition dipole moment (ETDM) in the PFBT main chain (Fig. 4c, d). Polarization mapping, reconstructed from a series of polarized FL images, confirms the counterclockwise spiral alignment of the PFBT main chains on the surface of (S)-TB-MS (Fig. 4e and Supplementary Fig. S16a), which is further corroborated by the polarized FL images collected at θ = 0° (Fig. 4f and Supplementary Fig. S16b, c). These images correspond well with a twisted director field line in an LC droplet with a TB arrangement.^{32, 33}

These results are informative for explaining the azimuthally selective WGMs and their λ_em-dependent angular movement along the circumference. Because FL radiates perpendicularly to the direction of the ETDM, FL at the surface of (S)-TB-MS is preferentially directed towards Q1 and Q3 and is confined via TIR. Accordingly, the peculiar surface orientation of PFBT results in the right-left asymmetric WGM PL images in Fig. 3f, which is schematically drawn in Fig. 4g. Moreover, due to the distinct anisotropy in the extraordinary and ordinary refractive indices (n_e and n_o, respectively) of the PFBT main chain,³⁴ the swirl molecular orientation makes the morphologically spherical surface an optically anisotropic surface along the latitudinal angle. As a result, the diagonal optical pathways on (S)-TB-MS show a λ-dependent optical path length, as depicted in Fig. 4g.

To verify the λ-dependent angular shift of the WGM, we constructed an analytical model and conducted numerical simulations. In our model, we suppose that the bipolar axis of (S)-TB-MS is aligned along the y-axis, and the WGM orbits a great circle inclined by φ from the x- towards the y-axis (Fig. 5a). Here, the effective permittivity \(⟨\epsilon ⟩\) along the WGM trajectory is given by tracking the orientation of PFBT (p) along the circle. Since the TE modes are expected to be sensitive to the molecular orientation due to the tangential anchoring of the main chain of PFBT on the surface of the microsphere, the φ -dependent shift of the WGM resonance frequency is simulated by substituting \(⟨\epsilon ⟩\) for the resonance condition of the TE mode (Eq. S2 in the Supporting Information). In this context, the electric field component in the travelling direction (\(\widehat{\phi }\)) of the WGM is sufficiently small with respect to that in the perpendicular direction (\(\widehat{\theta }\)). Therefore, \(⟨\epsilon ⟩\) is approximated as

\(⟨\epsilon ⟩\approx \frac{1}{2\pi }{\int }_{0}^{2\pi }{{n}_{e}}^{2}{\text{cos}}^{2}\xi \left(\phi \right)+{{n}_{o}}^{2}{\text{sin}}^{2}\xi \left(\phi \right)d\phi\)

where ε is the angle between p and \(\widehat{\theta }\) (Fig. 5a). In ε, the function f(y) characterizes the swirl pattern determined by the angle between p and the y-axis (see SI for details). Here, we assume \(f\left(y\right)={\varphi }_{e}\sqrt{1-{\left(\frac{2y}{d}\right)}^{2}}\) to dictate a twisted geometry, where φ_e represents the angle at which the ETDM crosses the equator of (S)-TB-MS (Fig. 5a; see SI for details). According to the detailed analysis of the polarized FL images shown in Fig. 4 and Supplementary Fig. 16, the φ_e of (S)-TB-MS is expected to be ~ 50°.

To simulate φ-dependent WGM resonance, four parameters, n_e, n_o, d, and φ_e, should be considered. As reliable values, we set n_e, n_o, and d as follows: n_e = 1.80 ± 0.05 and n_o = 1.55 ± 0.05 from reference ³⁴ and d = 4.4 ± 0.1 µm from the optical micrographs of (S)-TB-MS in Fig. 3c. Then, the φ_e value that well fits the experimental plots of φ in Fig. 3e is systematically assigned. The simulated curves with φ_e = 55° best fit the experimental results (Fig. 5b, Supplementary Fig. 17, and Supplementary Table 1), which is comparable to the experimentally obtained value (~ 50°). Furthermore, the analytical model indicates the appearance of WGM spots around the bipolar positions (φ = 70–120°), although it does not fit well at φ ~ 90°, possibly because of the disorder of the polymer arrangement at the topological defect position (spot (iii) in Fig. 3f and Supplementary Fig. 18). These results strongly suggest that the proposed swirl molecular orientation can indeed explain the azimuthally selective WGMs with an λ_em-dependent shift along the circumference.

As an enantiomeric control, the WGM resonance of (R)-TB-MS was also studied. In contrast to (S)-TB-MS, HSC images of (R)-TB-MS display resonant PL in the second and fourth quadrants (Q2 and Q4, respectively, Supplementary Fig. 19 and Supplementary Video 5). Furthermore, polarized FL images of (R)-TB-MS are mirror images to those of (S)-TB-MS, indicating that the swirl directions of the PFBT main chains on the surfaces of these spheres are opposite (Supplementary Fig. 20). These results corroborate that the origin of the azimuthally anisotropic WGM confinement in the TB microcavity can be attributed to chirality-dependent twisted alignment of the ETDM.

We demonstrated novel azimuthally selective WGMs for a supramolecularly chiral topological metasphere. The point chirality along the side chains of the π-conjugated polymer dictates the swirl topological texture on the TB microsphere self-assembled through supramolecular assembly. The mechanical and optical robustness of the microsphere allows manipulation of the microstructure subjected to HSC imaging, thus visualizing the generation of anomalous WGM resonance with azimuthally asymmetric trajectory. Polarized FL images visualize the swirl alignment of the polymer metasurface, which leads to asymmetric WGM emission. These results are further supported by theoretical simulations considering the swirl distribution of the refractive index on the sphere surface. These comprehensive investigations cannot be addressed through the use of fluidic LC droplets. This study examines the impact of topological metasurfaces on WGM resonances and expands 2D metasurfaces to quasi-3D non-Euclidean planes, offering new technology to manipulate light for applications in directional WGM lasers and vortex beam emitters with soft materials.^36–39

Acknowledgements

The authors acknowledge Prof. E.W. (Bert) Meijer, Prof. S.C.J. Meskers, and Dr. C. Kulkarni in Eindhoven University of Technology for the synthesis of chiral conjugated polymers and Prof. Jer-Shing Huang in Leibniz Institute for Photonics Technology for discussion on the optical properties. This work was supported by JST CREST (JPMJCR20T4, JPMJCR19T1) and JSPS KAKENHI (JP19J20398 and JP22H05131).

Author contribution

O.O. and Y.Y. designed the research; O.O. and S.N. conducted all experiments and analyzed the data; F.S. supported the fs pumping µ-PL measurements; W.L. and S.I. performed numerical simulations; O.O., H.Y., and Y.Y. prepared the manuscript.

Author information

Reprints and permissions information is available at www.nature.com/reprints. The authors declare no competing financial interests. Readers are welcome to comment on the online version of the paper. Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Correspondence and requests for materials should be addressed to O.O. ([email protected]) and Y.Y. ([email protected]).

Koenderink, A. F., Alu, A. & Polman, A. Nanophotonics: shrinking light-based technology. Science 348, 516–521 (2015), DOI: 10.1126/science.1261243
Taghinejad, M. & Cai, W. All-Optical Control of Light in Micro-and Nanophotonics. ACS Photon. 6, 1082–1093 (2019). DOI: 10.1021/acsphotonics.9b00013
Yan, Y.; Zhang, C., Yao, J. & Zhao, Y. S. Recent Advances in Organic One-Dimensional Composite Materials: Design, Construction, and Photonic Elements for Information Processing. Adv. Mater. 25, 3627–3638 (2013). DOI: 10.1002/adma.201300325
Vahala, K. J. Optical microcavities. Nature 424, 839–846 (2003). DOI: 10.1038/nature01939
Feng, S., Lei, T., Chen, H., Cai, H., Luo, X. & Poon, A. W. Silicon photonics: from a microresonator perspective. Laser Photon. Rev. 6, 145–177 (2012). DOI: 10.1002/lpor.201100020
He, L.; Özdemir, Ş. K.; Yang, L. Whispering Gallery Microcavity Lasers. Laser Photon. Rev. 7 (1) 60–82 (2013). DOI: 10.1002/lpor.201100032
Yang, S., Wang, Y. & Sun, H. Advances and Prospects for Whispering Gallery Mode Microcavities. Adv. Opt. Mater. 3, 1136–1162 (2015). DOI: 10.1002/adom.201500232
Gorodetsky, M. L., Savchenkov, A. A. & Ilchenko, V. S. Ultimate Q Optical Microsphere Resonator. Opt. Lett. 21, 453–455 (1996). DOI: 10.1364/OL.21.000453
Schubert, M. et al. Lasing within Live Cells Containing Intracellular Optical Micro-Resonators for Barcode-Type Cell Tagging and Tracking. Nano Lett. 15, 5647–5652 (2015), DOI: 10.1021/acs.nanolett.5b02491
Vattikunta, R. et al. Photonic Microresonators from Charge Transfer in Polymer Particles: Toward Enhanced and Tunable Two-Photon Emission. ACS Appl. Mater. Interfaces 10 (19), 16723–16730 (2018). DOI: 10.1021/acsami.8b01600
Du, Y. et al. Tuneable red, green, and blue single-mode lasing in heterogeneously coupled organic spherical microcavities. Light: Sci. Appl. 9, 151 (2020). DOI: 10.1038/s41377-020-00392-7
Tabata, K. et al. Self-Assembled Conjugated Polymer Spheres as Fluorescent Microresonators. Sci. Rep. 4, 5902 (2014). DOI: 10.1038/srep05902
Haehnle, B., Lamla, M., Sparrer, K. M. J., Gather, M. C. & Kuehne, A. J. C. Narrow Stimulated Resonance Raman Scattering and WGM Lasing in Small Conjugated Polymer Particles for Live Cell Tagging and Tracking. Adv. Opt. Mater. 9, 2001553 (2020). DOI: 10.1002/adom.202001553
Musěvic, I., Pajk, S., Humar, M. & Ravnik, M. Electrically tunable liquid crystal optical microresonators. Nat. Photon. 3, 595–600 (2009). DOI: 10.1038/nphoton.2009.170
Wang, Y., Li, H., Zhao, L., Liu, Y., Liu, S. & Yang, J. Tunable whispering gallery modes lasing in dye-doped cholesteric liquid crystal microdroplets. Appl. Phys. Lett. 109, 231906 (2016), DOI: 10.1063/1.4971973
Duan, R., Li, Y., Li, H. & Yang, J. Real-time monitoring of the enzymatic reaction of urease by using whispering gallery mode lasing. Opt. Express 10, 6073–6083 (2019). DOI: 10.1364/BOE.10.006073
Avino, S. et al. Direct Sensing in Liquids Using Whispering-gallery-mode Droplet Resonators. Adv. Opt. Mater. 2, 1155–1159 (2014). DOI: 10.1002/adom.201400322
Tang, S. K. Y. et al. A Multi-Color Fast-Switching Microfluidic Droplet Dye Laser. Lab Chip 9 (19), 2767–2771 (2009). DOI: 10.1039/b914066b
Yamagishi, H. et al. Pneumatically Tunable Droplet Microlaser. Laser Photon. Rev. 4 (4) 2200357 (2023). DOI: 10.1002/lpor.202200874
Xu, F. & Crooker, P. P. Chiral nematic droplets with parallel surface anchoring. Phys. Rev. E 56, 6853−6860 (1997). DOI: 10.1103/PhysRevE.56.6853
Miller, D. S., Wang, X. G. & Abbott, N. L. Design of Functional Materials Based on Liquid Crystalline Droplets. Chem. Mater. 26 (1), 496–506 (2014). DOI: 10.1021/cm4025028
Jeong, J., Davidson, Z. S., Collings, P. J., Lubensky, T. C. & Yodh, A. G. Chiral symmetry breaking and surface faceting in chromonic liquid crystal droplets with giant elastic anisotropy. Proc. Natl Acad. Sci. USA. 111, 1742−1747 (2014), DOI: 10.1073/pnas.1315121111
Darmon, A., Benzaquen, M., Copar, S., Dauchot, O. & Lopez-Leon, T. Topological defects in cholesteric liquid crystal shells. Soft Matter 12, 9280–9288 (2016). DOI: 10.1039/C6SM01748G
Pairam, E. et al. A. Stable nematic droplets with handles. Proc. Natl. Acad. Sci. U. S. A. 110, 9295−9300 (2013), DOI: 10.1073/pnas.1221380110
Kamien, R. The geometry of soft materials: a primer Rev. Mod. Phys. 74, 953– 971 (2002). DOI: 10.1103/RevModPhys.74.953
Oki, O. et al. Robust Angular Anisotropy of Circularly Polarized Luminescence from a Single Twisted-Bipolar Polymeric Microsphere. J. Am. Chem. Soc. 143 (23), 8772–8779 (2021), DOI: 10.1021/jacs.1c03185Di
Abbel, R., Schenning, A. P. H. J. & Meijer, E. W. Molecular weight optimum in the mesoscopic order of chiral fluorene (co)polymer films. Macromolecules 41, 7497−7504 (2008). DOI: 10.1021/ma8014855
Nuzzo, D. et al. High circular polarization of electroluminescence achieved via self-assembly of a light-emitting chiral conjugated polymer into multidomain cholesteric films. ACS Nano 11, 12713−12722 (2017). DOI: 10.1021/acsnano.7b07390
Zaumseil, J., Donley, C. L., Kim, J.-S., Friend, R. H. & Sirringhaus, H. Efficient top-gate, ambipolar, light-emitting field-effect transistors based on a green-light-emitting polyfluorene. Adv. Mater. 18, 2708– 2712 (2006). DOI: 10.1002/adma.200601080
Kushida, S., Okada, D., Sasaki, F., Lin, Z. H., Huang, J. S. & Yamamoto, Y. Low-threshold whispering gallery mode lasing from self-assembled microspheres of single-sort conjugated polymers. Adv. Opt. Mater. 5, 1700123 (2017). DOI: 10.1002/adom.201700123
Adachi, T. et al. Spherical Assemblies from π‑Conjugated Alternating Copolymers: Toward Optoelectronic Colloidal Crystals. J. Am. Chem. Soc. 135, 870-876 (2013). DOI: 10.1021/ja3106626
Oswald, P., Dequidt, A. & Poy, G. Lehmann Effect in Nematic and Cholesteric Liquid Crystals: A Review. Liq. Cryst. Rev. 7, 142–166 (2019). DOI: 10.1080/21680396.2019.1671244
Dubtsov, A. V. et al. Liquid Crystalline Droplets in Aqueous Environments: Electrostatic Effects. Soft Matter 14, 9619– 9630 (2018). DOI: 10.1039/c8sm01529e
Ramsdale, C. M. & Greenham, N. C. The optical constants of emitter and electrode materials in polymer light-emitting diodes. J. Phys. D: Appl. Phys. 36, L29 (2003). DOI: 10.1088/0022-3727/36/4/101
Lin, Z. H. et al. Impact of Plasmonic and Dielectric Substrates on the Whispering-Gallery Modes in Self-Assembled Fluorescent Semiconductor Polymer Microspheres. Nano Lett. 23, 14, 6512–6519 (2023). DOI: 10.1021/acs.nanolett.3c01463
Wang, Q. J. et al. Whispering-gallery mode resonators for highly unidirectional laser action. Proc. Natl Acad. Sci. USA. 107, 22407–22412 (2010). DOI: 10.1073/pnas.101538610
Brasselet, E., Murazawa, N., Misawa, H. & Juodkazis, S. Optical Vortices from Liquid Crystal Droplets. Phys. Rev. Lett. 103, 103103903 (2009). DOI: 10.1103/PhysRevLett.103.103903
M. Papič., U. Mur., K. P. Zuhail., M. Ravnik., I. Muševič. & M. Humar. Topological liquid crystal superstructures as structured light lasers. Proc. Natl Acad. Sci. USA. 118, 2110839118 (2021). DOI: 10.1073/pnas.2110839118
U. Mur. & M. Ravnik. Numerical modeling of optical modes in topological soft matter. Opt. Express 30, 14393-14407 (2022). DOI: 10.1364/OE.454980

There is NO Competing Interest.

SM1MicromanipulationPOM.mp4
Supplementary Dataset 1
SM2TBsMSatq9010nmsec.mp4
(S)-TB-MS_at_q=90°
SM3TBsMSatq010nmsec.mp4
(S)-TB-MS_at_q=0°
SM4aMS10nmsec.mp4
a-MS
SM5TBsMSRR10nmsec.mp4
(R)-TB-MS_at_q=90°
SupplementaryInformation.docx

Download PDF

Version 1

posted

You are reading this latest preprint version

Anomalous optical resonance on supramolecularly chiral metaspheres with a swirl topology

Status:

Version 1

Abstract

Figures

Introduction

Preparation of fluorescent TB microspheres

WGM PL from TB-MS

Azimuthally selective WGMs from TB-MS

Swirl arrangement of PFBT on the microsphere surface

Conclusion

Declarations

References

Additional Declarations

Supplementary Files

Status:

Version 1