Design of rare-earth doped chalcogenide microspheres for mid-IR optical amplification

The design of an optical amplifier based on an Er3+-doped chalcogenide microsphere evanescently coupled with a tapered optical fiber is illustrated. The physical phenomena as the main transitions among the erbium energy levels, the amplified spontaneous emission and the most important secondary transitions, pertaining to the ion-ion interactions, have been modeled in a 3D numerical code. The model is based on the coupled mode theory and the rate equations. The device has been designed and optimized by varying the fiber-microsphere gap, the thickness of erbium doped region, the fiber taper angle, the erbium concentration, the pump and signal powers. The simulation results highlight that the amplification system here proposed could be a good candidate to obtain a highly efficient and compact amplifier in mid-infrared wavelength range.