a Top view of the 180o bend, plus tapers and additional straight waveguides, connecting adjacent QPM NLO sections. The phase along the structure is tracked in b to ensure that an integer multiple of \(\Delta\mathrm{k}~=~2\pi\) rad. occurs at the output of the bend. c Plot of device area AD versus Lc (solid black curve) when L= 100 \(\mu\)m and Lt (dashed red curve) when L= 40 \(\mu\)m. For both curves, LNL = 1 cm and n = 10.