Optically induced mode splitting in self-assembled, high quality-factor conjugated polymer microcavities

Abstract

We investigate the whispering gallery modes (WGMs) of self-assembled single microspheres. They consist of a recently developed highly fluorescent π-conjugated copolymer and exhibit excellent optical properties with Q-factors up to 104. Under continuous laser irradiation, we observe a splitting of the highly degenerate spherical WGMs into a multiplet of lines. Comparison with the calculated spectral response of a weakly distorted sphere shows that the optical excitation induces a change of the optical path length in the microcavity so that it resembles a prolate spheroid. The separation of the lines is given by the ellipticity and the azimuthal mode number. Measurements in various gaseous environments suggest that the distortion is caused by light induced oxidation of the polymer. Our findings show that photooxidation can be a beneficial mechanism for in-situ tuning of optically active polymer structures.

Optical microresonator arrays of fluorescence-switchable diarylethenes with unreplicable spectral fingerprints

“…[16][17][18] The resultant spectrum, the so-called optical fingerprint, can be utilized as an identification tag, because the WGM spectral patterns are highly sensitive to the size, morphology, and refractive index of the resonators. [19][20][21] In this article, we demonstrate that self-assembled microarrays of photoswitchable optical resonators work as a PUF. The hemispherical microresonators are made of fluorescent photochromic diarylethenes (DAEs).…”

π-Conjugated nanostructured materials: preparation, properties and photonic applications

“…94 Conjugated polymer-based nano/microparticles have started to attract attention as optical nano/microcavities for lasing applications because of their high refractive indices, high absorptivity, high PL efficiency, and simple preparation methods. [95][96][97][98][99][100][101][102][103] Microcavities conne light with narrow resonance frequencies and have a variety of applications, including laser resonators, photon pair generation, and biosensors. A microcavity consists of a dielectric as a resonator and a uorescent dye to provide the optical activity.…”

“…The average Q-factor is dened as the peak wavelength divided by the full-width at the half maximum of the observed WGM PL peaks (Q av ). [100][101][102][103] Conjugated polymer-based microspheres have been used in single-component white-colour resonant micro-photoemitters. White PL was generated from microspheres composed of selfassembled polycarbazole polymer chains (PCz).…”

Self‐Assembled Organic Crystalline Microring Cavities with High Q‐Factors

“…These microcavities were fabricated entirely or partially using self‐assembly methods. The WGMs have been clearly observed for several of them, even in spontaneous emission spectra . High Q ‐factors have been observed in microspheres, and a channel add–drop filter has been demonstrated for a combination of nanofibers and a microring …”

“…The WGMs have recently been studied in many different organic optical microcavities, including self‐assembled microspheres,, microrings, microdisks, hemispheres, tubes, frustums, ellipsoid, and hexagonal disk . These microcavities were fabricated entirely or partially using self‐assembly methods.…”