An intelligent and monolithic integration of optical power splitter with optically switchable cross-connect has been proposed. It is fabricated on the multimode interference principle in Si-based SiGe material system and configured for a 332 symmetrical structure of the three input waveguides and the two output waveguides. The central waveguide section is based on a multimode interference and incorporated with an activated carrier injection element. The operating wavelengths of the device are specially designed for 1545, 1550, and 1555 nm conventional-band wavelengths. The measured crosstalk is at around −17 dB and the average insertion loss is about 5.25 dB. At switch-ON state, the measured injection current is 370 mA corresponding to an injection current density of 950 A/cm2.

A SiGe Mach-Zehnder interferometer modulator based on the plasma dispersion effect has been fabricated. A maximum modulation depth of 86% and a switching current of 40 mA with a π-phase-shift voltage of 0.9 V have been achieved at 1.3μm wavelength. The device has a measured insertion loss of 2.5dB and a response time of 238 ns.

A symmetrical digital photonic splitting switch with a low insertion loss and a low driving voltage is developed using carrier injection in a silicon-germanium material for optical communication systems and networks at a wavelength of 1.55 μm. The switch structure has been improved based on a traditional 1×2 Y−shaped configuration by using two widened carrier injection regions. The switch has a threshold voltage of 1.0 V and a corresponding threshold current of 85 mA on one of the two output waveguide arms. The calculated driving current density is 5.7 kA/cm2 and the calculated power consumption is 85 mW at the 85 mA of threshold current. The measured insertion loss and the crosstalk are 5.2 dB and −9.6 dB, respectively, at driving voltage over 2V.

Based on total internal reflection and plasma dispersion effect, a SiGe/Si asymmetric optical waveguide switch with transverse injection structure has been proposed and fabricated. The switch performance is measured at the wavelength of 1.55μm. A modulation depth of 90% at an injection current of 110mA is obtained, and the switching time is about 0.2μs. The device reaches a maximum optical switching at the injection current of 120mA. The extinction ratio is larger than 34dB and the crosstalk and insertion loss are less than -18.5 and 2.86dB, respectively.