Table 2.

Comparison of waveguide technology from literature (materials of the lower cladding/core/upper cladding, channel structure from Figure 3, principle from Figure 1).

Materials	Channel	Principle	References
Air/Si/Air	ridge	evanescent	[16,17,18,19,20,21,22,23,24,25,26,27,28,29]
		coupler	[30]
		direction	[31]
	PhC	evanescent	[32]
	slot	evanescent	[33]
GaAs/AlGaAs	ridge	direction	[34]
glass/doped glass/Air	diffused	evanescent	[8]
InP/InGaAsP	ridge	direction	[35,36]
		evanescent	[37,38,39,40,41,42]
metal/Air/metal (hollow)	reflection	evanescent	[43]
polymer/Air	ridge	coupler	[44,45,46,47]
polymer/polymer	ridge	direction	[48]
	buried ridge	coupler	[49]
SiO2/glass/Air	rib	strain	[4]
SiO2/Au	plasmon	evanescent	[50]
SiO2/Al2O3/SiO2	ridge	direction	[51]
SiO2/BK7/SiO2	strip-loaded	strain	[52]
SiO2/PS/Air	inverted rib	strain	[53]
SiO2/PSG/Air	rib	evanescent	[54]
SiO2/PSG/SiO2	buried rib	direction	[55,56,57,58,59,60,61,62]
		coupler	[63,64,65]
	buried ridge	coupler	[28]
SiO2/Si/Air	rib	coupler	[26,27]
SiO2/SiON/Air	rib	evanescent	[66,67,68,69]
	rib	strain	[70]
	rib ARROW	strain	[71]
	ridge	evanescent	[72,73,74,75]
SiO2/SiON/SiO2	buried ridge	coupler	[76]
	strip loaded	strain	[77,78,79]
	rib	evanescent	[80]
	inverse rib	direction	[6]
	buried rib	direction	[81]
SiO2/TiO2/Air	planar	evanescent	[7,82,83,84]