Valley filter of black phosphorus using irradiation by linearly polarized light

We propose a valley filter in the few-layer black-phosphorus-based n-p-n (BP-npn) junction, by applying linearly polarized light (LPL) in the scattering region. It is found that the considered BP can separate two good valleys in the presence of band gap inversion. Moreover, the LPL has been found to selectively match the pseudospin of the scattering region with the pseudospin of incident electrons in opposite valleys. This is more apparent than the valley polarization controlled by electric potential barriers. As LPL is strengthened, the null-polarization region decreases, leading to the widening of the regions of valley polarization. In addition, the width of the scattering region can cause substantial Fabry-P\'erot oscillations in tunneling, leading to a difference in $D\ensuremath{-}$ and $D+$ valley-dependent conductance, thereby improving valley polarization efficiency. Therefore, this junction can be a promising candidate for the valley filter.