Abstract:
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As we approach the limits in operating speed of IC’s predicted by Moore’s Law, some
alternative way of increasing velocities while reducing dimensions has to be found. In this
context, optical interconnects appear to be an optimal solution that avoids the main limitations
that electrical interconnects have.
To implement these optical interconnects in the already well developed CMOS integrated
environment, the System-in-Package (SiP) and the Silicon on Insulator (SOI) technologies arise
as a good solution to achieve these goals.
In this Thesis optical single mode strip nano waveguides and a grating coupler for vertical
coupling to optical fibres are presented, designed and simulated. Their design parameters are
optimized, and their performance analyzed and discussed.
Firstly, the characteristics of large single mode rib waveguides and their direct butt coupling to
fibres is studied. Their performance is found to be not good enough when the dimensions were
reduced to under 1 μm, with losses as high as 14.5 dB.
Therefore, nano strip waveguides are studied and simulated. They provide high light
confinement and good propagation characteristics. Some performance characteristics
(confinement factor, single mode region, effective index) are studied, for core widths in the
range 100 – 600 nm.
The vertical coupling of these nano strip waveguides to optical fibres by means of a grating
coupler is simulated with the FDTD technique. The main design parameters of this grating
coupler are optimized, obtaining losses of 7 dB for TE polarisation and 8.5 dB for TM. The
misalignment tolerances are also analysed.
The crosstalk effects between this grating and an hypothetical underlying waveguide are
studied, showing that no light couples to the lower waveguide. |