  The electron transport of different conical valleys is investigated in
graphene with extended line-defects. Intriguingly, the electron with a definite
incident angle can be completely modulated into one conical valley by a
resonator which consists of several paralleling line-defects. The related
incident angle can be controlled easily by tuning the parameters of the
resonator. Therefore, a controllable 100% valley polarization, as well as the
detection of the valley polarization, can be realized conveniently by tuning
the number of line-defects and the distance between two nearest neighbouring
line-defects. This fascinating finding opens a way to realize the valley
polarization by line-defects. With the advancement of experimental
technologies, this resonator is promising to be realized and thus plays a key
role in graphene valleytronics.
