Fig. 1. Schematic of the observation setup (not to scale). The observation volume can be scanned in 3D by acting on both scanner and focus. Inset: Measured CEF for the system.

Fig. 2. Raw stack of images taken for a 5 µm sphere illuminated at λ=520 nm. The microsphere is deposited on a glass substrate, the upper medium is air. The detection plane moves upwards (towards the bead) by steps of 500 nm between each 2D scan.

Fig. 3. (a) Reconstruction of the photonic jet generated by a 5 µm microsphere viewed along the optical axis. This refers to the stack of raw data displayed on Fig. 2. The effects of the CEF of our apparatus have been corrected here by numerical deconvolution (see text for details). The microsphere position is indicated by a white circle. (b) Cut along the horizontal axis at the best focus point. Red dots correspond to the measured data after CEF deconvolution, solid line is a Gaussian fit that emphasizes the Gaussian lineshape of the profile. (c) Intensity cut along the vertical axis at the center of the jet. Blue dots correspond to the measured data after CEF deconvolution. Solid line is a Lorenzian fit. The intensity has been normalized so that the incoming intensity (calibrated well outside the bead vicinity) is set to unity. Therefore, this cut directly shows the intensity concentration (enhancement) inside the photonic jet. (d) Full width at half maximum (FWHM) of the photonic jet measured for each 2D scan after CEF deconvolution (green dots). The dashed line corresponds to the FWHM of our numerical simulation for a 5 µm latex bead free standing in air.

Fig. 4. Same as Fig. 2 for a sphere of 3 µm diameter.

Fig. 5. Same as Fig. 3 for a sphere of 3 µm diameter.

Fig. 6. (1520 KB) Movie of the reconstructed photonic jet for a 3 µm sphere. [Media 1]

Fig. 7. Same as Fig. 2 for a sphere of 1 µm diameter.

Fig. 8. Same as Fig. 3 for a sphere of 1 µm diameter.

Fig. 9. Distribution of intensity obtained by numerical simulations. (a) Case of a 5 µm sphere. Dependance of FWHM of the jet versus propagation distance was plotted in Fig. 3 (d). (b) Case of a 3 µm sphere. Dependance of FWHM of the jet versus propagation distance was plotted in Fig. 5 (d). For both figures, the corresponding sphere location and size are indicated by a white circle. Note that the color levels have been normalized independently.

Fig. 10. Same as Fig. 2 for a group of 3 spheres of 3 µm diameter. Note that in this particular case, the detection plane moves towards the spheres by steps of 1 µm between each 2D scan.