Erbium-doped germanium-based sulphide optical waveguide amplifier for near- and mid-IR

Due to remarkable properties of the chalcogenide glasses (Chgs), especially sulphide glasses, amorphous chalcogenide films should play a motivating role in the development of integrated planar optical circuits and their components. This paper describes the fabrication and properties of optical waveguides of undoped and erbium doped sulphide films obtained by RF magnetron sputtering and laser ablation (PLD). The deposition parameters were adjusted to obtain, from sulphide glass targets with a careful control of their purity, layers with appropriate compositional, morphological, structural characteristics and optical properties. A transmission loss of 0.8 dB/cm can be obtained for rib waveguides produced by dry etching under CF4 plasma (4-300 μm wide, 5.5 μm film thickness, 1.5 μm etched thickness). The photo-luminescence of erbium doped Ge20Ga5Sb10S65 films were clearly observed in the n-IR and mid-IR spectral domain. The study of their decay lifetime with a well adapted annealing treatment controlling the roughness variation reached value of the bulk counterpart. Amplification tests were carried out leading to a complete characterisation of the Erbium doped waveguide. Gain on/off of 4.4 dB (3.4 dB/cm) were achieved for a signal at 1.54 μm in multiple modes sulphide:Er waveguides. The first demonstration of photoluminescence in mid-IR in an Er3+- doped Chg waveguide could potentially be employed to produce sources or amplifiers operating in the mid-IR.