Phase noise reduction of a semiconductor laser in a composite optical phase-locked loop

Abstract

The bandwidth and residual phase noise of optical phase- locked loops (OPLLs) using semiconductor lasers are typically con- strained by the nonuniform frequency modulation response of the laser, limiting their usefulness in a number of applications. It is shown in this work that additional feedback control using an optical phase modula- tor improves the coherence between the master and slave lasers in the OPLL by achieving bandwidths determined only by the propagation de- lay in the loop. A phase noise reduction by more than a factor of two is demonstrated in a proof-of-concept experiment using a commercial distributed feedback semiconductor laser. C 2010 Society of Photo-Optical Instru-