A planar waveguide junction comprising - at least one input waveguide section (172; 200; 228; 296; 302; 332; 362; 402), - at least two output waveguide sections (176, 178; 204, 206; 297, 298; 304, 306; 334, 336; 364, 366; 404, 406, 408) and - a transition waveguide section (180; 202; 220; 250; 270; 299; 308; 338; 368; 400) optically connecting the at least one input waveguide section (172; 200; 228; 296; 302; 332; 362; 402) and the at least two output waveguide sections (176, 178; 204, 206; 297, 298; 304, 306; 334, 336; 364, 366; 404, 406, 408), wherein the transition waveguide section comprises alternating gapped segments (182, 184; 222, 224, 226; 254; 310; 340; 370; 412) and ungapped segments (188; 230, 232, 234; 252, 256; 272, 280; 312; 342; 372; 414) along the optical path, the gapped segments (182, 184; 222, 224, 226; 254; 310; 340; 370; 412) having transverse to the optical path waveguide core segments corresponding to the at least two output waveguide sections (176, 178; 204, 206; 297, 298; 304, 306; 334, 336; 364, 366; 404, 406, 408) separated by gaps (186; 258; 282) in the optical core, and the ungapped segments (188;230,232,234;252,256;272,280;312;372;414) having transverse continuous core having a total width within ±10% of the total sum of transverse width of the core at the gapped segments (182, 184; 222, 224, 226; 254; 310; 340; 370; 412), - wherein the transition section has at least 3 gapped segments (182, 184; 222, 224, 226; 254; 310; 340; 370; 412) and at least 3 ungapped segments (188; 230, 232, 234; 252, 256; 272, 280; 312; 342; 372; 414), and - wherein the input section has a constant width segment along an optical path prior to and optically connected to a taper segment where the core widens and further along an optical path is connected to the transition section and wherein the gap (186; 258; 282) is from about 0.25 w to about 0.9 w, where w is the transverse extent perpendicular to the optical path of the input waveguide core along the constant width segment prior to the taper segment connected to the transition section. - at least one input waveguide section (172; 200; 228; 296; 302; 332; 362; 402), - at least two output waveguide sections (176, 178; 204, 206; 297, 298; 304, 306; 334, 336; 364, 366; 404, 406, 408) and - a transition waveguide section (180; 202; 220; 250; 270; 299; 308; 338; 368; 400) optically connecting the at least one input waveguide section (172; 200; 228; 296; 302; 332; 362; 402) and the at least two output waveguide sections (176, 178; 204, 206; 297, 298; 304, 306; 334, 336; 364, 366; 404, 406, 408), wherein the transition waveguide section comprises alternating gapped segments (182, 184; 222, 224, 226; 254; 310; 340; 370; 412) and ungapped segments (188; 230, 232, 234; 252, 256; 272, 280; 312; 342; 372; 414) along the optical path, the gapped segments (182, 184; 222, 224, 226; 254; 310; 340; 370; 412) having transverse to the optical path waveguide core segments corresponding to the at least two output waveguide sections (176, 178; 204, 206; 297, 298; 304, 306; 334, 336; 364, 366; 404, 406, 408) separated by gaps (186; 258; 282) in the optical core, and the ungapped segments (188;230,232,234;252,256;272,280;312;372;414) having transverse continuous core having a total width within ±10% of the total sum of transverse width of the core at the gapped segments (182, 184; 222, 224, 226; 254; 310; 340; 370; 412), - wherein the transition section has at least 3 gapped segments (182, 184; 222, 224, 226; 254; 310; 340; 370; 412) and at least 3 ungapped segments (188; 230, 232, 234; 252, 256; 272, 280; 312; 342; 372; 414), and - wherein the input section has a constant width segment along an optical path prior to and optically connected to a taper segment where the core widens and further along an optical path is connected to the transition section and wherein the gap (186; 258; 282) is from about 0.25 w to about 0.9 w, where w is the transverse extent perpendicular to the optical path of the input waveguide core along the constant width segment prior to the taper segment connected to the transition section.