Switching gain in semiconductor-based broadband all-optical switches is difficult to achieve. Current all-optical switching technologies based on silicon utilizes relatively weak χ(3) effect in the medium. Hence, most of the recent silicon-based all-optical switches are based on resonators that exploits resonance enhancement. Although, some of these switches exhibit switching gain, the bandwidth is severely limited .
On the other hand, there are SOA-based all-optical switches that are based on phase and gain modulation.
However, they require electrical driving power of ~0.5-2 W for biasing the medium to transparency and also strong and short control or data pulse to inhomogeneously saturate the medium via carrier depletion, carrier heating and spectral hole burning for modulating a weaker pump beam . So, even though SOA-based all-optical switches are broadband, switching gain is absent, they have large footprint and require high electrical energy. Hence, they are not suitable for sub-pico-joule energy efficient photonic links. So, in this work, we investigate a novel MZI-based broadband all-optical switch that: 1)doesnot require electrical driving – so the required energy is low, and 2) exhibits switching gain – so a weak data or control pulse switches or modulates a stronger pump beam. The proposed device is based on sub-micron direct band-gap semiconductor waveguides, based on GaAs or InGaAsP, heterogeneously-integrated on to passive waveguides that could be based on Silicon, Titanium Oxide etc. In this work we assume active material to be InGaAsP with bandgap corresponding to a wavelength of ~1.565 μm and passive material to be Silicon. In the next section, we investigate spatio-temporal switching properties of submicron waveguide, based on InGaAsP-based bulk medium. It is then followed by investigation of spatio-temporal switching properties of InGaAsP-based sub-micron waveguides in MZI configuration.