Enke Liu

Silicon on insulator Mach–Zehnder waveguide interferometers operating at 1.3 μm

Mach–Zehnder (MZ) waveguide interferometers integrated on SOI (silicon on insulator) for 1.3 μm operation are studied on the basis of the large cross‐section single‐mode rib waveguide condition and the free‐carrier plasma dispersion effect in Si wafer direct bonding SOI by back‐polishing. And the MZ interferometers are fabricated by using KOH anisotropic etching. Their insertion losses and modulation depths are measured to be 4.81 dB and 98%, respectively, at the wavelength of 1.3 μm when a forward bias voltage applied to a p+n junction is 0.95 V and the active zone length of the MZ interferometers is 816.0 μm.

1.55 μm reflection-type optical waveguide switch based on SiGe/Si plasma dispersion effect

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 1.55 μm. A modulation depth of 90% at an injection current of 110 mA is obtained, and the switching time is about 0.2 μs. The device reaches a maximum optical switching at the injection current of 120 mA. The extinction ratio is larger than 34 dB and the crosstalk and insertion loss are less than −18.5 and 2.86 dB, respectively.

Silicon-on-insulator asymmetric optical switch based on total internal reflection

Based on the large cross-section single-mode rib waveguide condition, total internal reflection (TIR) and the plasma dispersion effect, a silicon-on-insulator (SOI) asymmetric optical waveguide switch with transverse injection structure has been proposed and fabricated, in which the SOI technique utilizes silicon and silicon dioxide thermal bonding and back-polishing. The device performance is measured at a wavelength of 1.3 /spl mu/m. It shows that the extinction ratio and insertion loss are less than -18.1 and 6.3 dB, respectively, at an injection current of 60 mA. Response time is 110 ns.

Zero-gap directional coupler switch integrated into a silicon-on insulator for 1.3-μm operation

A silicon-on insulator (SOI) zero-gap directional coupler switch is studied based on the large-cross-section singlemode rib waveguide condition, the dual-mode interference principle, and the free-carrier plasma dispersion effect, in which the SOI technique uses silicon and silicon dioxide thermal bonding and backpolishing. The SOI is fabricated by potassium hydroxide anisotropic etching. Its insertion loss and cross talk are measured to be less than 4.81 dB and 218.6 dB, respectively, at a wavelength of 1.3 microm and a switching voltage of 0.91 V. Response time is ~210 ns.

Low-loss 1/spl times/2 multimode interference wavelength demultiplexer in silicon-germanium alloy

A low-loss multimode interference wavelength demultiplexer for 1.3- and 1.55-/spl mu/m operations based on the silicon-germanium alloy material has been proposed and demonstrated. The device was fabricated by molecular beam epitaxy followed by lithography and plasma etching. The input/output facets were polished mechanically. The measured insertion losses are 4.29 and 4.28 dB and the extinction ratios are 25 and 22 dB at 1.3 and 1.55 /spl mu/m, respectively.

Novel silicon waveguide switch based on total internal reflection

Novel silicon asymmetric optical switches with transverse injection structure have been proposed and fabricated which are based on total internal reflection and free‐carrier effect. The switches have a quite short operation length of about 200 μm. The device performance was measured at the wavelength of 1.3 μm. It shows that the crosstalk is less than −11.4 dB at an injection current of 85 mA. Response time is 100 ns. They are very suitable for silicon monolithic optoelectronic integration

Monolithic integration of a SiGe/Si modulator and multiple quantum well photodetector for 1.55 μm operation

The monolithic integration of a SiGe/Si rib waveguide modulator and multiple quantum well photodetector prepared by molecular beam epitaxy is achieved. The low dark current of 49.8 nA at −5 V reverse bias is measured and a modulation depth of 90% at 2.8 V modulation bias is obtained. The external quantum efficiency at λ=1.55 μm is estimated to be 18.2%.

Si1−xGex/Si asymmetric 2×2 electro‐optical switch of total internal reflection type

Based on plasma dispersion of Si1−xGex, we have fabricated asymmetric 2×2 switches of total internal reflection type, in which Si1−xGex was grown by molecular beam epitaxy. The optimum intersecting angle is 4°, and the crosstalk is less than −10.6 dB at 76 mA injection current. The insertion loss is 2.8 dB, and the switch time is 0.6 μs.

SiGe/Si Mach–Zehnder interferometer modulator based on the plasma dispersion effect

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 1.3 μm wavelength. The device has a measured insertion loss of 2.5 dB and a response time of 238 ns.

Integration of wavelength signal divider and infrared photodetectors based on the plasma dispersion effect in SiGe/Si

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 1.55 μm 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 1.55 μm, respectively. The insertion losses are 2.01 and 2.64 dB for 1.3 and 1.55 μm, respectively. At −5 V reverse bias, the dark currents of the detectors at the 1.3 and 1.55 μm 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 1.55 μm 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 1.55 μm output branches, respectively.