  Optical frequency combs, with precise control of repetition rate and
carrier-envelope-offset frequency, have revolutionized many fields, such as
fine optical spectroscopy, optical frequency standards, ultra-fast science
research, ultra-stable microwave generation and precise ranging measurement.
However, existing high bandwidth frequency control methods have small dynamic
range, requiring complex hybrid control techniques. To overcome this
limitation, we develop a new approach, where a home-made intra-cavity
electro-optic modulator tunes polarization state of laser signal rather than
only optical length of the cavity, to steer frequencies of a
nonlinear-polarization-rotation mode-locked laser. By taking advantage of
birefringence of the whole cavity, this approach results in not only broadband
but also relative large-dynamic frequency control. Experimental results show
that frequency control dynamic range increase at least one order in comparison
with the traditional intra-cavity electro-optic modulator technique. In
additional, this technique exhibits less side-effect than traditional frequency
control methods.
