46 research outputs found
Coherence effects in propagation through photonic crystals
We have analytically studied how a partially coherent quasi plane wave is affected by a photonic crystal structure including a grating. The analysis is presented for spatial and temporal cases showing the possibility to determine the coherence characteristics of the pulse.
Spectral properties for 1D multilayer systems and application to super resolution
The spectral properties of one-dimensional multilayer structures for the two polarizations TE and TM are investigated and a physical explanation for the large spatial transmission band that can be obtained with this kind of system is given together with a discussion of the correlated super resolution effect. A designing approach to build 1D metal-dielectric multilayer structures that have super resolution is also suggeste
Oblique frozen modes in periodic layered media
We study the classical scattering problem of a plane electromagnetic wave
incident on the surface of semi-infinite periodic stratified media
incorporating anisotropic dielectric layers with special oblique orientation of
the anisotropy axes. We demonstrate that an obliquely incident light, upon
entering the periodic slab, gets converted into an abnormal grazing mode with
huge amplitude and zero normal component of the group velocity. This mode
cannot be represented as a superposition of extended and evanescent
contributions. Instead, it is related to a general (non-Bloch) Floquet
eigenmode with the amplitude diverging linearly with the distance from the slab
boundary. Remarkably, the slab reflectivity in such a situation can be very
low, which means an almost 100% conversion of the incident light into the
axially frozen mode with the electromagnetic energy density exceeding that of
the incident wave by several orders of magnitude. The effect can be realized at
any desirable frequency, including optical and UV frequency range. The only
essential physical requirement is the presence of dielectric layers with proper
oblique orientation of the anisotropy axes. Some practical aspects of this
phenomenon are considered.Comment: text and 9 figure
A graphical environment to express the semantics of control systems
We present the concept of a unified graphical environment for expressing the
semantics of control systems. The graphical control system design environment
in Simulink already allows engineers to insert a variety of assertions aimed
the verification and validation of the control software. We propose extensions
to a Simulink-like environment's annotation capabilities to include formal
control system stability, performance properties and their proofs. We provide a
conceptual description of a tool, that takes in a Simulink-like diagram of the
control system as the input, and generates a graphically annotated control
system diagram as the output. The annotations can either be inserted by the
user or generated automatically by a third party control analysis software such
as IQC or -tool. We finally describe how the graphical
representation of the system and its properties can be translated to annotated
programs in a programming language used in verification and validation such as
Lustre or C