Contemporary and Future Trends in Optics - Optical Signal Processing by Silicon Photonics - page 14

As a solution to this problem pumping is done at wavelengths beyond 2.2 μ m due
to the reason that the TPA-induced free carriers are absent. Four Wave-Mixing can
take place over a wide bandwidth, by making a proper pump wavelength choice, due
to the reason that the waveguide lengths are much smaller, they showed. The use
of four wave-mixing in silicon waveguides is elaborated sufficiently, for generating
correlated photon pairs that are useful for quantum applications.
Foster et al. [ 4 ] used phase-matched FWM in properly designed silicon wave-
guides in order to describe 29 nm range amplification and conversion of wave-
length in efficient manner, ranging between 1,511 and 1,591 nm. The crucial
characteristic of their work is the design of the waveguides suitably in order to
fabricate irregular group-velocity dispersion in this management of wavelength.
Unlike the Raman Effect in silicon, the supple FWM's pump-signal detuning,
allows both the signal and pump to exist in the communications band. Through
parametric wavelength conversion and optical parametric oscillation, this advance-
ment makes possible the implementation of from a single pump laser in all-silicon
photonic integrated circuit. Moreover, all-optical switches, all optical delays, opti-
cal sources and optical signal regenerators for quantum information technology,
which have been realized using four wave-mixing in silica fibers, can be ported to
the SOI platform. FWM amplification depends critically on the phase mismatch
between the pump, signal and idler waves.
Liang et al. [ 5 ], discussed in their research the conventional silicon-based
optical switching device's switching speed, based on plasma dispersion effect
is restricted by the lifetime of free carriers which introduce either absorption or
phase changes. They neither state all-optical NOR gate logic which is independent
of free carriers but rely on two-photon absorption. Pump induced non-degenerate
two-photon absorption causes high speed operation, inside the silicon wire wave-
guides of submicron size. For logic gate operation, the device needed low pulse
energy (few pJ).
Lee et al. [ 6 ], carried out work and showed ultra-broadband wavelength conver-
sion in silicon photonic waveguides at 40 Gb/s data rate. The device which is built
in such a way that they avoid dispersion, elaborates a bandwidth conversion span-
ning the entire L - , C -, and S -bands of the ITU grid. For using a continuous-wave
-band pump, the 1,513.7 nm wavelength input signal is up-converted across nearly
50 nm with 40 Gb/s data rate, and bit-error rate measurements are performed on
the converted signal.
They selected a Dense Wavelength-Division Multiplexing operation on the
ITU—band's channel C50 to couple the probe beams and pump. The wavelengths
of probe and pump were chosen for providing conversion bandwidth which is the
largest bandwidth that can be allowed by the tunable laser and tunable filters. The
trace of the sample OSA shows the 47.7 nm conversion from 1,513.7 nm wave-
length input probe to a converted 1,561.4 nm wavelength of with conversion
efficiency near 18 dB having 40 Gb/s data rate. A visible degradation in optical
signal-to-noise ratio of converted signal can be observed due to the conversion
losses. For this reason, the efficiency of the wavelength converter is one of its most
crucial parameters for systems-level integration.