Extreme Mid-IR light control with SiC microstructures
Devarapu, Ganga Chinna Rao
Date: 9 June 2014
Thesis or dissertation
Publisher
University of Exeter
Degree Title
PhD in Physics
Abstract
In this thesis, we present our original theoretical investigations of SiC microstruc-tures for extreme light control in the Reststrahlen band of Silicon Carbide (SiC),
that occurs in the Mid-IR spectral regime. In this frequency regime, most of the
light will be reflected from bulk SiC, due to the extreme permittivity response of ...
In this thesis, we present our original theoretical investigations of SiC microstruc-tures for extreme light control in the Reststrahlen band of Silicon Carbide (SiC),
that occurs in the Mid-IR spectral regime. In this frequency regime, most of the
light will be reflected from bulk SiC, due to the extreme permittivity response of SiC.
However, we demonstrate that it is possible to control light to be absorbed or ultra
refracted within the microstructures constructed from SiC in the Reststrahlen band
of SiC. In particular, we show that this high reflective behaviour of SiC can be over-come via different mechanisms: by achieving a Photonic Crystal (PC) band-edge
reflectionless condition in a SiC terminated one-dimensional (1D)-PC, by tailoring
the effective phonon-polariton gap in SiC-based effective metamaterials, or by cou-pling to cavity modes in SiC structures made of rectangular-cross-section pillars.
Furthermore, we demonstrate that by varying the thickness of SiC layers and filling
ratio throughout SiC 1D-PC structures or by using SiC pillars of different size in a
pyramid arrangement, we can achieve a broad absorption bandwidth with the SiC
microstructures. This absorption control provides insight for the design of efficient
thermal emitters, which can be used in thermal conversion devices. Moreover, us-ing the concept of Bloch impedance, we find that translucent spectral regions can
exist in SiC 1D-PCs. This possibility is highly desirable for constructing optical
components in the Mid-IR spectrum where suitable bulk highly refractive materials
are rare. In addition, we also present a complete theory of propagation in lossy
1D-PCs, by systematically extending the comprehensive theory for lossless 1D-PCs.
Relying on this theory, we report superbending of light, beyond 90
0
in a judiciously
designed superprism constructed with a SiC 1D-PC. Since, the findings reported
in this thesis are in principle applicable to any polar material, we believe that our
work will inspire the design of a variety of absorptive/emissive and ultra-refractive
devices across the THz/Mid-IR spectrum.
Doctoral Theses
Doctoral College
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