Higher order planar-waveguide Bragg grating on curved waveguide

Sidewall gratings in ultra-low-loss Si_3N_4 planar waveguides

“…There have been prior results reported on sidewall grating technologies that include patterning through reactive-ion etching [6] and direct-write spatial-phase-locked electronbeam lithography [7]. Previous results in low loss, highly selective gratings include surface relief gratings integrated with aluminum oxide ridge waveguides [8] and sidewall gratings fabricated within a curved waveguide structure on a low loss silica platform [9]. Prominent results in these approaches have bandwidths on the order of 0.12 nm with coupling constant values of roughly 4.5 cm −1 [10].…”