Digital Signal Processing Reference
In-Depth Information
The lack of an effective photodetector for such applications has affected the
development of scalable SOI interconnections. For CMOS-compatible processing
the photodetector must be made from silicon (Si) or germanium (Ge), but Si is
transparent from wavelength range of 1.1-1.8
μ
, hence if Si waveguide is to be
used then we have to focus on this range only. Using Ge is advantageous but the
refractive index gap between Si and Ge makes it unsuitable for a monolithically
integrated Si photonics. Ge is also suffered by its large dark current, impaired
bandwidth, multimode nature, and inefficient waveguide to detector coupling.
Germanium or GeSi on Si provides detection of optical signals at 1.3-1.5
μ
m.
Luxtera demonstrated the Germanium-enabled SOI CMOS process and Intel pro-
duced an avalanche photodiode of Ge and Si [
46
,
47
].
A silicon-waveguide photodetector is exposed, comprising a waveguide layer
where only single mode light of a fixed polarization is guided/confined, and a
detection layer formed on the waveguide layer where guided light is detected [
48
].
Luxtera patented a germanium on silicon waveguide photodetector (disposed on
SOI substrate) which generates an electric current when an infrared optical signal
travels through the photodetector [
49
].
Michael et al. designed a silicon photo-detector device comprising a nanoscale
silicon high-contrast waveguide, an optical input, and an electrical output. The
distribution across the waveguide in optical mode has peak intensity in corre-
spondence to the nanoscale silicon waveguide's surface states [
50
]. In Fig.
5.6
an
equivalent designed structure's electrical circuit is shown (Fig.
7.7
).
DC Voltage
Source
synchronization
AC Voltage
Source
Lock- in
Amplifier
Signal
Current
Output
Modulator driver
Voltage
Modulator
1550nm light
CW 1550NM
Light
Laser
Optical
modulator
Modulator
detector
Fig. 7.7
An equivalent electrical circuit of the designed structure [
49
]
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