Design of Mid-IR Er3+-doped microsphere laser

A mid-IR lasing system based on a tapered fiber coupled to an Er3þ-doped microsphere has been modeled and numerically investigated. In order to design and optimize the device performance, a dedicated 3-D numerical code exploiting the coupled mode theory and the rate equations model has been developed. The main energy level transitions among the Er3þ ions, the most relevant secondary ion–ion interactions, the amplified spontaneous emission, and the fiber-microsphere coupling phenomena have been taken into account. In order to optimize the lasing performance, several parametric simulations have been carried out. The obtained numerical results show that a laser threshold of about 55m Wand an output power of about 17.8 dBm can be obtained by using small microspheres.