A laser frequency control apparatus comprising: (a) a laser; (b) an oscillator configured to receive an output of the laser and to output a modulated signal; (c) a frequency reference configured to receive the modulated signal and to provide an output signal; and (d) a mixer configured to mix at least a portion of the output signal with an output of the oscillator to generate a mixer output, wherein the mixer output is injected to a section of the laser.