Yongbo Tang

Device and Integration Technology for Silicon Photonic Transmitters

The device and integration technology for silicon photonic transmitters are reviewed in this paper. The hybrid silicon platform enables on-chip lasers to be fabricated with silicon photonic circuits and can be integrated in the CMOS back-end flow. Laser arrays from multiple die bonding and quantum well intermixing techniques are demonstrated to extend the spectral bandwidth from the laser array of the transmitter. Two modulator technologies, silicon modulators and hybrid silicon modulators, are also described.

Low threshold and high speed short cavity distributed feedback hybrid silicon lasers.

In this paper we investigate reducing threshold and improving the efficiency and speed of distributed feedback hybrid silicon lasers. A low threshold current of 8.8 mA was achieved for a 200 μm cavity at 20 °C. A 3 dB bandwidth of 9.5 GHz as well as 12.5 Gb/s direct modulation of DFB laser diode was achieved on the hybrid silicon platform for the first time.

Over 67 GHz bandwidth hybrid silicon electroabsorption modulator with asymmetric segmented electrode for 1.3 μm transmission

A distributed III-V-on-Si electroabsorption modulator based on an asymmetric segmented electrode has been developed on the hybrid silicon platform for the 1.3 μm transmission window. The measured modulation response shows a 2 dB drop at 67 GHz and an extrapolated 3 dB bandwidth of 74 GHz. Large signal measurements show clearly open eye diagrams at 50 Gb/s. An extinction ratio of 9.6 dB for back to back transmission and an extinction ratio of 9.4 dB after 16 km transmission were obtained with a drive voltage of 2.2 V.

50 Gb/s hybrid silicon traveling-wave electroabsorption modulator

We have demonstrated a traveling-wave electroabsorption modulator based on the hybrid silicon platform. For a device with a 100 μm active segment, the small-signal electro/optical response renders a 3 dB bandwidth of around 42 GHz and its modulation efficiency reaches 23 GHz/V. A dynamic extinction ratio of 9.8 dB with a driving voltage swing of only 2 V was demonstrated at a transmission rate of 50 Gb/s. This represents a significant improvement for modulators compatible with integration of silicon-based photonic integrated circuits.

Realization of an ultra-short silicon polarization beam splitter with an asymmetrical bent directional coupler

An ultra-short (~10 μm long) polarization beam splitter (PBS) based on an asymmetrical bent directional coupler (DC) is demonstrated experimentally by using silicon-on-insulator nanowires. The bent DC is designed to cross-couple TM polarized light completely while there is almost no coupling for TE polarization. Grating couplers are introduced at both ends of the PBS for efficient coupling to single-mode fibers. The measurement results show that the extinction ratios of the fabricated ultra-short PBS are higher than 10 dB for both polarizations in a broad wavelength range. It is also shown that the present PBS has a large fabrication tolerance.

Integrated Hybrid Silicon Transmitters

We review recent progress made on the hybrid silicon platform towards realizing an integrated WDM transmitter on silicon. Using ion implantation enhanced quantum well intermixing, four band gaps are integrated on a single chip and used to demonstrate a DFB laser-EAM array. The latest results on design changes to improve Mach-Zender and EA modulator performance are also described and the prospects for fabricating an integrated terabit per second transmitter on silicon are presented.

Energy-Efficient Hybrid Silicon Electroabsorption Modulator for 40-Gb/s 1-V Uncooled Operation

This letter demonstrates a high-speed and energy-efficient lumped electroabsorption modulator on the hybrid silicon platform for an uncooled operation at up to 80^°C . This 100-μm-long modulator has a 3-dB bandwidth of 30 GHz. Eye diagrams measured at the temperatures of 20^°C , 40^°C, 60 ^°C, and 80^°C with corresponding adjustment on the input wavelength and the bias voltage show a dynamic extinction ratio of around 5 dB at 40 Gb/s with a 1-V drive voltage swing and an energy consumption of 112 fJ/bit.

Realization of a Novel

The first experimental demonstration of a novel ring resonator-based 1 × N optical power splitter is reported. We fabricate the device on a Si3N4 waveguide platform utilizing a bonded thermal oxide upper cladding. Fiber coupling and near-held-imaging experiments at 1550 nm show that a 1 × 16 power splitter achieves very low excess loss of 0.9 dB in addition to excellent uniformity of 0.4 dB. The resonances of the device show a loaded quality factor of 6 million and hnesse of 100. The device is promising for high-port-count power splitters without the need for cascaded stages. We also discuss applications requiring the wavelength selectivity of the device.

1\times{\rm N}

Decreasing energy limits for data transport have resulted in efforts to reduce energy consumption in optical interconnects. The authors introduce three possible integration techniques for realizing a hybrid silicon transmitter on a single chip with distributed feedback (DFB) lasers and electro-absorption modulators. They review the current bottlenecks and techniques for further reducing threshold current and increasing the wall-plug efficiency of these lasers.

Power Splitter With Uniformly Excited Ports

A hybrid silicon traveling-wave electroabsorption modulator has been demonstrated. 43 GHz bandwidth and over 10 dB static extinction ratio are achieved for a 100 µm long device.