Complete Report - University of New South Wales

(a)
(b)
Figure 4.6.7: (a) Top view of the T-shaped intersection of silicon waveguide; (b) top view of a
LED (or a detector) at one end of the waveguide.
Again the infrared CCD camera was used to take photos of the light pattern in this waveguide
system. Figure 4.6.8 shows some of these photos. Here, the LED in the waveguide unit was
also forward biased. Similarly to the image in Figure 4.6.2(b), Figure 4.6.8(a) shows infrared
light emission from the left-side LED. However, no light was observed within the waveguide
in this photo.
(a)
(b)
Figure 4.6.8: The emitted infrared light images (a) for the LED at 100 mA forward bias; (b)
for the entire silicon waveguide system with prolonged signal accumulation, and with a low
external illumination to show the aluminium patterns.
In Figure 4.6.8(b), a very long accumulation period for the image was selected, which gave
a very brightly glowing LED emitter on the left. A low bias illumination was also added in to
show the aluminium patterns, which indicate the location of the LED and detectors. In Figure
4.6.8(b), the light from LED travelling inside the silicon waveguide could not be observed.
However, a bright spot at the T-intersection of the waveguide is observed. This indicates that
the light is indeed travelling along the silicon waveguide.
In future research, we plan to improve the light emission and detection effi ciencies for these
LED and detectors. These may be achieved using photonic crystals or plasmon structures.
The light absorption in the waveguide should also be reduced. This may be achieved by using
SiNx as the waveguide material rather than absorptive silicon.
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