  Simulation of detecting photoelectrons using multi-level multi-electron
(MLME) finite-difference time-domain (FDTD) method with an application to
near-field subwavelength imaging based on semiconductor nanophotodetector (NPD)
array is reported. The photocurrents from the photodiode pixels are obtained to
explore the resolution of this novel NPD device for subwavelength imaging. One
limiting factor of the NPD device is the optical power coupling between
adjacent detector pixels. We investigate such power coupling in the presence of
absorbing media as well as the spatial distributions of the electric field and
photoelectron density using the MLME FDTD simulation. Our results show that the
detection resolution is about one tenth of the operating wavelength, which is
comparable to that of a near-field scanning optical microscope based on metal
clad tapered fiber.

Optics;Computational Physics