GeO2SiO2 thin films for planar waveguide applications

Aqueous Suspensions of Highly Disperse Silica and Germania/Silica

“…Also, in amorphous germania, the Ge-O-Ge angle distribution is relatively narrow but wider than that for Si-O-Si in amorphous silica (5). The formation of Si-O-Ge bridges in GS synthesized by the sol-gel method occurs without phase segregation (6). Consequently, the structural difference between germania and silica in amorphous glasses or disperse powders (where Ge is mainly fourfold coordinated) can be less than that between titania and silica in disperse TiO 2 /SiO 2 , in which the crystalline phase of titania forms at 3-5 wt% and Ti atoms are mainly sixfold coordinated (4,7,8).…”

Violet upconversion emission of sol–gel neodymium-doped GeO2–SiO2 thin films via organically modified silane precursors

“…Among the different systems which can be obtained by sol-gel technique, GeO 2 -SiO 2 has been recognized as being excellent for obtaining optical waveguide films with controllable refractive index [4,5] and a large concentration dopant of rare-earth ions [6,7].…”

Low-loss as-grown germanosilicate layers for optical waveguides

“…7 Although there is no systematic study of propagation loss in germanosilicate planar waveguides, the reported values range between 3.5 and 10 dB/cm 1,2 at ϭ632.8 nm and are larger than 2 dB/cm at ϭ1.55 m. 8 To reduce the loss, it is common practice to anneal the as-grown layers at temperatures as high as 1100°C for prolonged times. 1,9 Recently, Zhang et al 9 reported CVD-grown germanosilicate planar waveguides with propagation losses of about 2 and 1 dB/cm at wavelengths of 632.8 and 1550 nm, respectively. However, due to low index contrast, almost half of the mode power in those waveguides propagate in the cladding material, the effect of which is not taken into account in the reported loss values.…”

“…Among them germanosilicate films ͓SiO x :Ge or (SiO 2 ) x :(GeO 2 ) 1Ϫx ] attract special interest due to their excellent compatibility with single-mode fibers. 1 Using germane as the core dopant and silica as the substrate, ensures nearly identical characteristics for planar waveguides with the existing fiber technology. Moreover, promising phenomena such as significant UV photosensitivity 2 and second-harmonic generation 3 have already been shown in germanosilicate waveguides, providing great potential for optical applications.…”

“…Moreover, promising phenomena such as significant UV photosensitivity 2 and second-harmonic generation 3 have already been shown in germanosilicate waveguides, providing great potential for optical applications. 4 Planar germanosilicate layers are conventionally grown by rf sputtering, 3 sol-gel methods, 1 powder melting, 5,6 or plasma-enhanced chemical vapor deposition ͑PECVD͒ techniques. 4 As-deposited SiO x :Ge optical waveguides grown with these methods all share the shortcomings of having relatively large propagation losses at wavelengths of 632.8 nm and 1.55 m. In particular, loss at ϭ1.55 m is known to be caused mainly by N-H and O-H bonds incorporated into the film matrix, while loss at 632.8 nm is due mainly to scattering mechanisms.…”