The optical response of PtSi/p‐Si Schottky barrier detectors structured with a lamellar grating was investigated. The quantum efficiencyYfor TE and TM polarized light for different samples with grating constants &Lgr;=3 &mgr;m, 4 &mgr;m, 5 &mgr;m, and with a grating amplitudeh=1100 nm was measured. The ratioYTM/YTEstrongly depends on the back bias of the diode. Theoretical calculations are presented which explain the results taking into account the locally varying Schottky barrier height and optical absorption induced by the grating. ©1995 American Institute of Physics.