The photodetachment cross section of H^- near two perpendicular elastic
planes is investigated in this paper. Both the traditional quantum approach and closed
orbit theory are applied to explicitly derive the formulas of the cross section for different
laser polarization direction. We first compared the quantum formulas with closed
orbit theory formulas, and then found that the quantum results are shown to be in
good agreement with the semiclassical results. Further more, we also found that the
cross section depends strongly on the direction of the laser polarization. When the polarization
is parallel to the closed orbit, the corresponding oscillation in the cross section
is very obvious. However, When the polarization is perpendicular to the closed
orbit, the corresponding oscillation is too small for closed-orbit theory formula to describe.