Fig. 1. (a) Schematic diagram of the growth mechanism of the PS/DCM microspheres. (b) Schematic diagram for the optical measurement.

Fig. 2. (a) The top view and (b) 45° view of SEM images of DCM-doped polymer microspheres.

Fig. 3. (a) The PL emission of a typical DCM-doped polymer microsphere recorded as a function of excitation density. (b) The emission intensity dependence on the excitation density. The inset in (b) is the corresponding fluorescent microsphere image (3.7 μm). (c) The relationship between λ2/Δλ and the diameter of the microsphere. (d) Lasing spectra of polymer microspheres with different diameters. The corresponding mode numbers are given in (d).

Fig. 4. (a) Experimental and simulated lasing spectra of individual sphere with a diameter of 3.7 μm. The inset shows the PL spectrum of DCM-doped PS film. (b) Electronic field distribution of resonance wavelength.

Fig. 5. (a) Schematic diagram of PL measurement under different RH. (b) Wavelength shift of the lasing mode under the exposure of different RH.

Fig. 6. (a) Normalized simulated lasing spectra of PS sphere with refractive index variation. (b) Relationship between wavelength shift and refractive index variation.

Fig. 7. Experimentally measured spectra taken from the PS microsphere before and after the water vapor treatment.