High germanium content waveguide materials

A planar optical device comprising:

• a waveguide core and waveguide cladding, wherein at least one of the waveguide core and the waveguide cladding is a germanium-silicon oxynitride glass having a Ge/(Si+Ge) mole ratio of from about 0.25 to about 0.47 and an N/(N+O) mole ratio of less than about 0.1.

A method of forming a planar optical device on a silicon substrate, wherein the device includes a waveguide baying a refractive index of from about 1.48 to about 1.52 at 1550 nm, and a coefficient of thermal expansion of from about 3×10−6° C.−1 to about 4.4×10−6° C.−1, comprising:

• depositing on a silicon substrate by plasma enhanced chemical vapor deposition a germanium-silicon oxide or oxynitride cladding layer having a Ge/(Si+Ge) mole ratio of from about 0.25 to about 0.47 and an N/(N+O) mole ratio of 0 to about 0.1;
• depositing on the cladding layer by plasma enhanced chemical vapor deposition a germanium-silicon oxide or oxynitride core layer having a Ge/(Si+Ge) mole ratio of from about 0.25 to about 0.47 and an N/(N+O) mole ratio of 0 to about 0.1, wherein the refractive index of the core layer is higher than the refractive index of the cladding layer.

A planar optical device comprising:

• a waveguide core and waveguide cladding, wherein at least one of the waveguide core and the waveguide cladding is a silica-germania-titania glass having a Ge/(Si+Ge+Ti) mole ratio of from about 0.08 to about 0.17 and a Ti/(Si+Ge+Ti) mole ratio of less than about 0.08.