Fig. 2: Photon density mode experiments.
a, Top: a resin cylinder with no core. Bottom: the measured spatial profiles (horizontal line-outs from the full two-dimensional image), for cylinders with a radius of 1, 2 and 2.5 cm (the photograph shows an example of a 2.5-cm-radius cylinder). The solid line shows the data, and the dashed lines show parameter-free fits with Bessel functions. b, Top: a resin cylinder (2.5 cm radius) with a straight (empty) core. Bottom: an experimental line-out for rcore = 0.5 mm (solid curve) and a fit with a modified Bessel function of the second kind (dashed curve). Inset: the same data for rcore = 1 mm. c, Top: a resin cylinder (2.5 cm radius) with a bent (empty) core. Bottom: results for three different bend radii of 5.5 cm, 3.5 cm and 2.8 cm and also a ‘no core’ sample. Note that the 5.5 cm core intensity is ~2× higher than the 3.5 cm core intensity, while the cladding profiles are nearly identical and barely distinguishable in the figure. The top photographs in all figures show the resin structures illuminated with a red laser. The insets in the main graphs show a schematic ‘cut-out’ of the resin waveguide structures to visualize the internal structure.
