Figure 4

SEM images of crossing 3D waveguides. (a) Top view of a set of waveguides crossing at their center, making an angle of ~ 50° between them. Both waveguides are 180 μm long. (b) Tilted view of the set of crossing waveguides, the higher waveguide (height ~ 75 µm) is fabricated first and the second one (height ~ 25 µm) is fabricated last to avoid lensing effects of the laser beam. The resulting waveguides have a core size of, approximately, 9 × 28 µm². Printing parameters: zig-zag period T = 0.3 μm, laser fluence F = 8.8 mJ cm⁻² for the waveguide core and F = 19.8 mJ cm⁻² for the tapers, stage velocity v = 100 µm s⁻¹.