Near-field optical fiber probe optimized for illumination–collection hybrid mode operation

The structure of a near-field probe was optimized for illumination-collection hybrid mode $\mathrm{(I–}\mathrm{C\hspace{0.17em}mode})$ operation. We developed a highly sensitive probe with a sharp-edged aperture and a double-tapered structure fabricated by a chemical etching technique. Through measurement of the photoluminescence (PL, λ=1 μm) image of single quantum dots, the performance of many versions of the probe with different aperture diameters, ranging from 80 to 500 nm, was systematically evaluated. In addition to the throughput and spatial resolution, the absolute value of the PL collection efficiency of the probe in $\mathrm{(I–}\mathrm{C\hspace{0.17em}mode})$ was also estimated for the first time. A collection efficiency several times greater than that of an objective lens with a numerical aperture of 0.8 was achieved with high spatial resolution in the 130–200 nm $\text{(λ/8–λ/5)}$ range.