4 research outputs found
Inverse scattering of 2d photonic structures by layer-stripping
Design and reconstruction of 2d and 3d photonic structures are usually
carried out by forward simulations combined with optimization or intuition.
Reconstruction by means of layer-stripping has been applied in seismic
processing as well as in design and characterization of 1d photonic structures
such as fiber Bragg gratings. Layer-stripping is based on causality, where the
earliest scattered light is used to recover the structure layer-by-layer.
Our set-up is a 2d layered nonmagnetic structure probed by plane polarized
harmonic waves entering normal to the layers. It is assumed that the dielectric
permittivity in each layer only varies orthogonal to the polarization. Based on
obtained reflectance data covering a suitable frequency interval,
time-localized pulse data are synthesized and applied to reconstruct the
refractive index profile in the leftmost layer by identifying the local,
time-domain Fresnel reflection at each point. Once the first layer is known,
its impact on the reflectance data is stripped off, and the procedure repeated
for the next layer.
Through numerical simulations it will be demonstrated that it is possible to
reconstruct structures consisting of several layers. The impact of evanescent
modes and limited bandwidth is discussed
The effect of gain saturation in a gain compensated perfect lens
The transmission of evanescent waves in a gain-compensated perfect lens is
discussed. In particular, the impact of gain saturation is included in the
analysis, and a method for calculating the fields of such nonlinear systems is
developed. Gain compensation clearly improves the resolution; however, a number
of nonideal effects arise as a result of gain saturation. The resolution
associated with the lens is strongly dependent on the saturation constant of
the active medium.Comment: to appear in J. Opt. Soc. Am.