Microwave-assisted in situ laser dye incorporation into high sensitivity whispering gallery mode microresonators

Abstract

Optical whispering gallery mode microresonators (WGM-µRs) are powerful sensitive components with many analytical applications. Here, spherical WGM-µRs have been synthesised in a single-step microwave (MW)-assisted heterophase polymerisation. The microresonators are based on poly(styrene) beads into which the organic lasing dye nile red was incorporated as gain medium in situ during the polymerisation. The particle diameter and diameter distribution of the synthesised particles were tuned in the range of around 200 nm up to 50 µm by adjusting the concentration between stabiliser poly-(N-vinyl pyrrolidone) (PVP) and monomer styrene, and the solvent composition in the dispersion process. Lower water content enabled the synthesis of spherical particles with large size polydispersity, from which WGM-µRs with a variety of diameters were selected. Microspheres with diameters ≳3.5 µm supported WGMs. The WGMs were excited through free space via the fluorescence of the laser dye. Pumping power levels <1 µW were sufficient to excite WGMs. WGM shifts of beads with diameter between ≈5 and 30 µm measured in air and water show a sensitivity up to 54 nm/RIU for the smallest particles. Dye doped WGM-µR in the low µm size range obtained by the

High Q Ultra‐Low Threshold Lasing in Conjugated Polymer Blend Microspheres Promoted by FRET

“…Microlasers with different resonator geometries such as rings, [28,29] toroids or spheres based on luminescent organic dyes or conjugated polymers (CPs) have been reported, [30][31][32] with typical Q factors in the 10 3 range. These observations have indeed prompted applications of these microlasers as highly sensitive sensors as well as for labelling and tracking cells in a biological medium.…”

Magnetothermally-responsive nanocarriers using confined phosphorylated halloysite nanoreactor for in situ iron oxide nanoparticle synthesis: A MW-assisted solvothermal approach

“…The reactor configuration enables the MW energy to be applied directly inside the reaction medium, using a coaxial antenna [60,61]. This method has already been successfully used to synthesize a wide gamma of different materials like superparamagnetic IONs [31], silver nanoparticles [62], dye-doped polymeric microresonators [63] and mesoporous ordered silica-based frameworks [64].…”