A comprehensive analytical approach towards cascaded second-order nonlinearities was presented. The nonlinear phase shifts by cascading in type Ⅱ second harmonic generation were investigated anlytically. The results show that type Ⅱ second harmonic generation can lead to large intensity dependent phase shifts for the input beams under a variety of conditions, provided that the orthogonal input components have unequal amplitudes. The analytical results can be used to optimize the process of cascaded second-order nonlinearties to obtain a certain phase shift with minimum power requirements. The effect of intensity dependent polarization rotation induced by the nonlinear phase shifts and a kind of all-optical polarization switching based on this effect were analyzed and discussed. These results are quite appealing for developing a new all-solid passive mode-locking femto-second laser device based on the polarization switching.