Controlling light within microscopic spaces is crucial for next-generation optical devices such as photonic integrated circuits and localized sensors. Microspheres formed of luminescent π-conjugated polymers act as optical resonators that confine and amplify light via whispering gallery modes (WGMs), and they are promising candidates for microscale organic lasers and photonic applications. However, conventional microsphere resonators are geometrically isotropic and emit isotropic light, making directional control of emissions challenging.
In a new study published in the Journal of the American Chemical Society, researchers from the University of Tsukuba show that microspheres formed through the self-assembly of chiral π-conjugated polymers possess a characteristic twisted bipolar molecular configuration, enabling angle-selective optical resonance and laser oscillation with distinct azimuthal directionality. Using polarization-dependent photoluminescence imaging, the research team directly visualized a vortex-like (swirling) arrangement formed by the polymer main chains on the spherical surface.
Furthermore, this vortex-like surface molecular orientation induces an azimuth-dependent refractive-index distribution along the light propagation path, resulting in angle-dependent WGM resonance wavelengths and spatially localized emission. Consequently, the microspheres exhibit directional laser oscillation, preferentially emitting amplified light along a specific azimuthal direction. The resulting emission pattern is analogous to Saturn's rings.
This work presents the first demonstration of controlled light-emission directionality in a spherical resonator achieved by exploiting topological molecular ordering on the microsphere surface.
Publication details
Osamu Oki et al, Angle-Selective Optical Resonance and Circular Radial Lasing from a Chiral Polymeric Microsphere, Journal of the American Chemical Society (2026). DOI: 10.1021/jacs.6c01819
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Citation: Saturn-ring-like laser emission from chiral polymeric microspheres (2026, July 7) retrieved 14 July 2026 from https://phys.org/news/2026-07-saturn-laser-emission-chiral-polymeric.html
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