Mingbin Yu

Silicon Modulators and Germanium Photodetectors on SOI: Monolithic Integration, Compatibility, and Performance Optimization

Si modulators and Ge photodetectors are monolithically integrated on Si-on-insulator. The carrier-depletion-type Si modulators achieved high modulation efficiency and speed (<i>V</i> _¿ <i>L</i> _¿ = 2.56 V·cm, 10 Gb/s). Low-voltage operation (<i>V</i> _RF = 1 <i>V</i> _pp) was also demonstrated. Introducing a low-thermal-budget postepitaxy anneal improves the performance of the Ge photodetectors, thus resulting in significantly improved dark current. The responsivity and speed in the low-voltage regime are also enhanced, which enhances low-voltage or even short-circuit (<i>V</i> _Bias = 0 V) operation.

A high-density MIM capacitor (13 fF/μm/sup 2/) using ALD HfO 2 dielectrics

Metal-insulator-metal (MIM) capacitors with different HfO/sub 2/ thickness have been investigated. The results show that both the capacitance density and voltage coefficients of capacitance (VCCs) increase with decreasing HfO/sub 2/ thickness. In addition, it is found that the VCCs decrease logarithmically with increasing thickness. Furthermore, the MIM capacitor with 10-nm HfO/sub 2/ shows a record high capacitance density of 13 fF//spl mu/m/sup 2/ and a VCC of 607 ppm/V, which can meet the requirement of the International Technology Roadmap for Semiconductors. It can also provide a low leakage current of 5.95 /spl times/ 10/sup -8/A/cm/sup 2/ at room temperature at 1 V, low tangent values below 0.05, and a small frequency dependence. These results indicate that the devices are suitable for use in silicon integrated circuit applications.

Demonstration of directed XOR/XNOR logic gates using two cascaded microring resonators

We propose and demonstrate a directed optical logic circuit that can perform the XOR and XNOR logic operations consisting of two cascaded microring resonators, i.e., an upper waveguide and an under waveguide. No waveguide crossings exist in the circuit, which is very useful to improve the signal quality and reduce the insertion loss of the device. As proof of principle, XOR and XNOR logic operations with the speed of 10 kb/s are successfully demonstrated. In addition, numerical simulation results indicate that the length difference between the upper waveguide and the under waveguide can change the output spectrum characteristics of the device, which acts like a Mach-Zehnder interferometer (MZI).

Silicon-Waveguide-Based Mode Evolution Polarization Rotator

A mode-evolution-based polarization rotator in silicon waveguide was designed. The rotators performance was studied under different launching conditions. The rotator with minimum length of 40 ?m was demonstrated to provide the polarization rotation with polarization extinction ratio of 15 dB. The insertion loss at the transition region was less than 1 dB.

WDM multi-channel silicon photonic receiver with 320 Gbps data transmission capability.

A high performance monolithically integrated WDM receiver is fabricated on the SOI platform, with key components comprising a 1 x 32 Si-based AWG and an array of high speed waveguided Ge-on-Si photodetectors. The optical channel spacing is 200 GHz. This configuration was used to demonstrate 32-channel operation in the L-band, where it is particularly challenging for silicon photonics due to the low absorption coefficient of Ge at L-band wavelengths. Each channel is capable of operating at a data rate of at least 10 Gbps, resulting in an aggregate data rate of 320 Gbps. At a BER of 1 x 10(-11), the WDM receiver showed an optical input sensitivity between -16 dBm and -19 dBm.

Observation of femtojoule optical bistability involving fano resonances in high-Q/Vm silicon photonic crystal nanocavities

The authors observe experimentally optical bistability enhanced through Fano interferences in high-Q localized silicon photonic crystal resonances (Q∼30000 and modal volume ∼0.98 cubic wavelengths). This phenomenon is analyzed through nonlinear coupled-mode formalism, including the interplay of χ(3) effects such as two-photon absorption and related free-carrier dynamics, and optical Kerr as well as thermal effects and linear losses. Experimental and theoretical results demonstrate Fano resonance based bistable states with switching thresholds of 185μW and 4.5fJ internally stored cavity energy (∼540fJ consumed energy) in silicon for scalable optical buffering and logic.

Ultralow Power Silicon Photonics Thermo-Optic Switch With Suspended Phase Arms

In this letter, a 2 × 2 thermo-optic waveguide-based switch with ultralow power consumption is demonstrated and fabricated using a standard complementary metal-oxide-semi conductor (CMOS) process. The phase arms are suspended by removing adjacent SiO2 and 120 μm of the underlying Si, while leaving a few SiO2 beams to support the suspended phase arms for the purpose of structural strength. As compared to the switch without isolation layer, a significant reduction of >;98% in power consumption is achieved. It is realized by preventing the heat from leaking out of the phase arms due to the presence of the air isolation layer. Our device shows an extinction ratio of over 23 dB at 1550 nm for TE mode with an ultralow power consumption of 0.49 mW. The response time is 266 μs, including the raise time of 144 μs and the fall time of 122 μs.

Observation of four-wave mixing in slow-light silicon photonic crystal waveguides

Four-wave mixing is observed in a silicon W1 photonic crystal waveguide. The dispersion dependence of the idler conversion efficiency is measured and shown to be enhanced at wavelengths exhibiting slow group velocities. A 12-dB increase in the conversion efficiency is observed. Concurrently, a decrease in the conversion bandwidth is observed due to the increase in group velocity dispersion in the slow-light regime. The experimentally observed conversion efficiencies agree with the numerically modeled results.

Near-infrared waveguide-based nickel silicide Schottky-barrier photodetector for optical communications

Integrated silicon-on-insulator waveguide-based silicide Schottky-barrier photodetectors were fabricated using low-cost standard Si complementary metal-oxide-semiconductor processing technology. The thin epitaxial NiSi2 layer formed by solid-state Ti-interlayer mediated epitaxy on the top of Si-waveguide absorbs light propagating through the waveguide effectively and exhibits excellent rectifying property on both p-Si and n-Si. NiSi2∕p-Si detectors with tapered geometry demonstrate dark current of ∼3.0nA at room temperature, responsivity of ∼4.6mA∕W at wavelengths ranging from 1520to1620nm, and 3dB bandwidth of ∼2.0GHz. The approaches for further improvement in responsivity are addressed.

Thermal independent Silicon-Nitride slot waveguide biosensor with high sensitivity

As the sensitivity and detection limit of photonic refractive index (RI) biosensor increases, the temperature dependence becomes a major challenge. In this paper, we present a Mach-Zehnder Interferometer (MZI) biosensor based on silicon nitride slot waveguides. The biosensor is designed for minimal temperature dependence without compromising the performance in terms of sensitivity and detection limit. With air cladding, the measured surface sensitivity and detection limit of MZI biosensor reach 7.16 nm/(ng mm(-2)) and 1.30 (pg mm(-2)), while achieving a low temperature dependence is 5.0 pm/° C. With water cladding, the measured bulk sensitivity and detection limit reach 1730(2π)/RIU and 1.29 × 10(-5) RIU respectively. By utilizing Vernier effect through cascaded MZI structures, the measured sensitivity enhancement factor is 8.38, which results in a surface detection limit of 0.155 (pg mm(-2)).