Fig. 1. Schematic for transverse writing of reconfigurable 2×2 DC based on depressed cladding waveguides. Circular cladding composed of dozens of parallel filaments formed through single scan using a longitudinal discrete ring-shaped focal intensity profile. The ring is tilted 10° with respect to x axis.

Fig. 2. (a) 3D isosurface of the targeted 3D focal intensity profile (the isosurface is given by the intensity at 45% of the peak value). (b) Calculated phase mask. (c) Corresponding simulated 3D isosurface intensity profile. The sample is translated along y axis.

Fig. 3. Optical micrographs and guided modes of a waveguide written through the discrete ring-shaped focal field. (a) Cross section of the depressed cladding. (b) Top view of the waveguide. (c), (d) 2D intensity distribution images of the guided H and V polarization modes at 1550 nm, respectively.

Fig. 4. Optical micrographs; numerical simulation of the electric field between the two electrodes and guided mode of a DC written by using the discrete ring-shaped focal field. (a) Top views of the straight interaction region (middle) and two curved segments (left and right) of the DC without the integrated electrodes. (b) Top view of the electrodes and their connecting lines. Inset: connecting line with a pad at the end. (c) Equipotential contour of the electric field around the electrodes. (d) Splitting ratio with the increase in applied voltage to the electrode. (e) Output intensity of the DC for the guided V mode at 1550 nm with three voltages.