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|Title: ||Propagation loss in slow light photonic crystal waveguides|
|Authors: ||Schulz, Sebastian Andreas|
|Supervisors: ||Krauss, Thomas F.|
|Issue Date: ||20-Jun-2012|
|Abstract: ||The ﬁeld of nanophotonics is a major research topic, as it offers potential solutions to
important challenges, such as the creation of low power, high bandwidth interconnects or
optical sensors. Within this ﬁeld, resonant structures and slow light waveguides are used
to improve device performance further. Photonic crystals are of particular interest, as they
allow the fabrication of a wide variety of structures, including high Q-factor cavities and
slow light waveguides.
The high scattering loss of photonic crystal waveguides, caused by fabrication disorder,
however, has so far proven to be the limiting factor for device applications. In this thesis, I
present a detailed study of propagation loss in slow light photonic crystal waveguides.
I examine the dependence of propagation loss on the group index, and on disorder, in
more depth than previous work by other authors. I present a detailed study of the relative
importance of different components of the propagation loss, as well as a calculation method
for the average device properties.
A new calculation method is introduced to study different device designs and to show that
photonic crystal waveguide propagation loss can be reduced by device design alone. These
“loss engineered” waveguides have been used to demonstrate the lowest loss photonic crystal
based delay line (35 dB/ns) with further improvements being predicted (< 20 dB/ns).
Novel fabrication techniques were investigated, with the aim of reducing fabrication
disorder. Initial results showed the feasibility of a silicon anneal in a nitrogen atmosphere,
however poor process control led to repeatability issues.
The use of a slow-fast-slow light interface allowed for the fabrication of waveguides spanning multiple writeﬁelds of the electron-beam lithography tool, overcoming the problem of
The slow-fast-slow light interfaces were combined with loss engineering waveguide designs, to achieve an order of magnitude reduction in the propagation loss compared to a W1
waveguide, with values as low as 130 dB/cm being achieved for a group index around 60.|
|Publisher: ||University of St Andrews|
|Appears in Collections:||Physics & Astronomy Theses|
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