Photoinduced Bragg gratings in multilayer channel waveguides of chalcogenide glasses

摘要

In recent years, amorphous chalcogenide gksses (ChG) have attracted much attention for applications in infrared communication systems and integrated optical circuits High transparency in the 1-10 μm wavelength region, large nonlinear index of refraction, and low phonon energy of ChG make them very useful for applications in both passive and active photonic devices. The ChG also exhibit high photosensitivity when exposed at a wavelength corresponding to band gap energy The photosensitive effects, among them photodarkening and photoexpansion, provide the photo-imprinting of a variety of volume and surface periodic and guided wave structures in ChG thin films In this work, we present the first demonstration of Bragg reflectors at 1550 nm in multilayer As-S-Se/As-S based planar and channel waveguides. The multilayer waveguide is used because of higher coupling efficiency and stronger nonlinear characteristics compared with the single layer structure. AS_2S_3 (α ～ 10~3 cm~(-1) @ 514 nm) was shown to be more photosensitive than As_(24)S_(38)Se_(38) (α ～ 10~4 cm~(-1)), but the latter has a much higher non-linear index of refraction (n_2 ～ 1.75 x 10~(-14) cm~2/W).