Abstract We introduce the simulation of a photonic crystal slab with a square lattice, whose basis elements are layered cylinders of an averaged refractive index <n>. We compare it with a similar photonic crystal with a basis of the same size and a refractive index matching to the average of the layered ones. Even when this is such a simple system with internal structure, we have found an interesting phenomenology: an increase in band gaps, flattening of the bands, degeneracy nodes, etc. We also introduce additional methods to fine tuning the design and analyze the inclusion of a plain cylinder defect within the slab.
Talbot self-images localization is important in many optical applications such as interferometry, metrology
and nanolithography. Usually, the problem of self-images localization is reduced to the finding the planes of
maximal light pattern visibility. There are several conventional techniques that determine the contrast of an intensity
distribution generated by a periodical object, such as root mean square (RMS) method, and variogram-based method.
In all these cases, a CCD camera is used to record the light patterns that are processed and analyzed in order to find
the self-image position. Recently, it has been proposed the use an adaptive photo-detector based on the non-steadystate
photo-electromotive force (photo-EMF) effect, which uses periodically oscillating light pattern to induce
alternating current through the short-circuited photoconductive sample. Here we perform the theoretical analysis of
the technique based on the photo-EMF effect against the conventional methods for the localization of the Talbot
patterns.
We present the experimental study of a new method that uses an adaptive photodetector based on the nonsteady-
state photoelectromotive force (photo-EMF) effect for measuring the visibility of the Talbot patterns generated by a Ronchi grating. It was demonstrated that the photo-EMF based detector could be used for efficient localization of planes with minimal and maximal visibility in real time, with high spatial resolution and without any
signal processing. The possibility for localization of self-images in turbid media was also investigated. Finally, the
performance of our method was compared against conventionally used method based on analysis of images obtained by CCD camera.
The detectors based on non-steady-state photo-electromotive force (p-EMF) effect, induced in a photoconductor by
an oscillating light pattern, have been proposed recently for localization of self-images generated by a periodical
object in real time and without any image processing. Here, we present the detailed theoretical analysis of the p-
EMF effect induced by an arbitrary 1-D periodical light pattern. Analytical expression for p-EMF current density in
a case of light distribution containing only odd harmonics is derived. In order to illustrate our results, axial
dependence of the photo-EMF signal induced by patterns generated in near field by the diffraction on a binary
grating was simulated numerically. Our results demonstrated, that the optimum regime for the localization of selfimages
using the p-EMF based detector is when the fundamental spatial harmonic of the light pattern is smaller than
the inverse of the diffusion length of the charge carriers, being the p-EMF current proportional to the sum of the
squares of the spatial harmonics visibilities.
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