Linewidth narrowing of a DFB semiconductor laser at 1.55 μm by optical injection of an Er:ZBLAN microspherical laser

An Er:ZBLAN microspherical laser has several laser lines around 1.55 μm with narrow bandwidths (∼ 50-100 kHz). Such a laser is used as a master laser to optically inject a slave DFB semiconductor laser. We show that the slave can be easily locked by one microsphere mode only, enabling a spectral narrowing of the laser line (from 30 MHz to 67 kHz). We stress the selective process of light amplification and filtering effect by the DFB slave.