Based on the two-mode interference principle, the high carrier injection effect, and the free-carrier plasma dispersion effect, a directional coupling active optical switch in SiGe/Si alloy has been fabricated. Its insertion loss and crosstalk were measured to be 2.74 and -15.5dB, respectively, at the wavelength of 1.3μm and the total switching current of 110 mA. The fastest response time of the switch is up to 30 ns.

Based on the plasma dispersion effect, a single-mode SiGe wavelength signal divider (WSD) integrated with infrared photodetectors for optical communication at the wavelengths of 1.3 and 1.55μm is proposed and fabricated by molecular beam epitaxy. The device performances are measured. The crosstalks of the WSD at a forward modulation bias of 1.2 V are -25 and -18 dB at 1.3 and 1.55μm, respectively. The insertion losses are 2.01 and 2.64 dB for 1.3 and 1.55μm, respectively. At -5 V reverse bias, the dark currents of the detectors at the 1.3 and 1.55μm output branches are 45 and 64 nA, respectively. Photocurrent responsivities of 0.08 and 0.07 A/W for the two detectors at the 1.3 and 1.55μm output branches have been achieved. The quantum efficiencies of the whole WSD and detector integration system are estimated to be about 19% and 18.2% for the 1.3 and 1.55μm output branches, respectively.

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.

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.

An ultracompact, multifunctional, and highly integrated photonic switch with a 3