All-Optical Frequency Shifting - Optical Signal Processing by Silicon Photonics - page 93

7.14 Other Optical Signal Processing Chip-Scale Devices

As the SOI has offered a promising platform for complete monolithic integra-
tion of Si-photonic devices, numerous signal processing devices have been con-
structed recently. Optical filters are designed in [ 51 , 52 ] but most suffer from
polarization dependence due to structural birefringence offered by the waveguides.
Transmission spectrum of the ring resonator filter with polarization diversity has
designed which works well for both polarizations (TE and TM), and polarization-
dependent loss is about 1 dB [ 53 ].Optical splitters, attenuators, pulse shapers,
optical delay lines, optical logic gates (AND, NOT, NAND, NOR, OR, XOR, and
XNOR), etc., have been successfully demonstrated using nonlinear properties of
silicon.
Chip-scale optical delay lines (buffers) were proposed using slow light propa-
gation [ 54 ], or coupled resonator waveguide [ 55 ] and cascaded microring resona-
tor by IBM Inc., which consists of 100 resonators producing about 200 ps delay.
A novel-shaped microdisk resonator is presented to overcome evanescent coupling
through a narrow gap and offers gap-less nonevanescent light coupling with mode
matching [ 56 ]. An SOI-based variable optical attenuator (VOA) is designed in
which propagating light is absorbed by the injected carriers and shows nanosecond
temporal response [ 57 ].
In Poon and Xu [ 58 ] a 5 × 5 Si photonic optical router is demonstrated com-
prising electro-optic switchable micro-ring resonators in cascaded form, coupled
tangentially into a network of cross-grid waveform, to lessen the insertion loss
due to waveguide crossing and decrease the leakage to the crossed waveguides;
waveguide crossings based on MMI is used. An SOI-based optical interconnection
arrangement is provided that significantly reduces the size, complexity, and power
consumption of conventional high density electrical interconnections. A group of
optical modulators and wavelength division multiplexers/demultiplexers are used

Silicon
Photonic
Waveguide

f pump

f probe

f probe

f fidler

f pump f probe

f fidler f pump

Fig. 7.8 FWM, using two pump waves in 3R regeneration [ 61 ]