In a solid-state imaging element, reflecting layers are provided on both
sides of a photoelectric conversion means, a light entrance window 128 is
provided in the first reflecting layer 121 disposed on the photon
incidence side, and a concentration means 122 is provided at a position
corresponding to the window. Further, a transparent layer 136 is provided
between the photoelectric conversion means and a second reflecting layer
120. A structure where photons that entered between the two reflecting
layers do not flow outside is preferably employed as the shape of the
second reflecting layer 120. According to the present invention,
detection sensitivity of a solid-state imaging element and a
photo-detector using the same is improved, and a personal authentication
system carrying a photo-detector showing improved detection sensitivity
is provided.