Some new phenomena of orthogonally polarized lights are observed in the laser-feedback system and in the new system that combines the frequency splitting technique with laser feedback. Results show that there are obvious mode competition between orthogonally polarized lasers throughout the laser-feedback process. This mode competition shows randomness. Further analysis shows that this mode competition between orthogonally polarized lights can effectively increase the laser intensity changing rate relative to the piezoelectric transducer voltage, which provide a new way to improve the axial resolution of a laser-feedback microscope.