Frequency stabilization of a directly modulated semiconductor laser

A method for stabilizing the center frequency of a directly modulated semiconductor laser is described. The laser frequency is locked to a Fabry–Perot etalon by controlling both the injection current and temperature by a frequency error signal simultaneously. The square root of the Allan variance obtained here is 2.5×10−13<σy(τ)<4.0×10−13 for the sampling time 1 s<τ<1000 s.