  Offset locking is a popular method for stabilizing laser frequency, which is
crucial to many physics experiments. Wide range offset locks are desirable, as
they increase the span of usable frequencies in an experiment. Here, we
experimentally realize a wide-range offset lock using a beat-note setup
combined with electro-optic phase modulation. By using frequency
down-conversion of the beat note and locking to sidebands generated by
electro-optic modulation, we achieve an offset range of $\pm$ 220.1 GHz with
offset frequency fluctuations under 0.1 Hz, enabling an optical heterodyne
offset lock with the largest known range of any such lock. The relative
simplicity of our setup provides a compelling method for locking at offsets in
the hundreds of GHz range.
