Fig. 1. (a) TEM image of a typical needle-shaped β-BBO NC (scale bar = 100  nm). (b) HR-TEM image of an individual needle showing two nanocrystallites, marked by round curves (scale bar = 10  nm).

Fig. 2. Raster scan images. (a) Single emitter recorded without using a spatial filter; (b) CM (10 μm pinhole).

Fig. 3. (a) Spectrum of the observed SH emission (inset: spectrum of the excitation laser). (b) SH signal dependence on the excitation laser average power.

Fig. 4. Polarization response characterized by (θ0, ϕ0) for some single nanoparticles (approximated lengths: 800 nm). From (a) to (d) the NC’s c-axis orientations are (78°, 76°), (87°, 88°), (73°, 87°), and (79°, 64°). The straight lines represent the directions of the NC’s c-axis.