Fiber coupled Er3+: Chalcogenide microsphere amplifier in mid-IR wavelength range

A mid-IR amplifier constituted of a tapered chalcogenide fiber coupled to an Er
³⁺
-doped chalcogenide microsphere has been optimized via a particle swarm optimization (PSO) algorithm. The numerical model is based on the coupled mode theory and on the erbium rate equations, including the main transitions among the ion energy levels. The PSO has allowed the optimal choice of the microsphere and taper fiber radius, fiber angle taper, fiber-microsphere gap in order to maximize the amplifier gain, which is close to G=7 dB, calculated for a pump power Pp = 100 mW and the input signal power P
_s
= -50 dBm, at signal wavelength λ=4500 nm.