Showing papers by "Hong Liang published in 2011"

30GHz Ge electro-absorption modulator integrated with 3 μm silicon-on-insulator waveguide.

Abstract: We demonstrate a compact waveguide-based high-speed Ge electro-absorption (EA) modulator integrated with a single mode 3 µm silicon-on-isolator (SOI) waveguide. The Ge EA modulator is based on a horizontally-oriented p-i-n structure butt-coupled with a deep-etched silicon waveguide, which transitions adiabatically to a shallow-etched single mode large core SOI waveguide. The demonstrated device has a compact active region of 1.0 × 45 µm(2), a total insertion loss of 2.5-5 dB and an extinction ratio of 4-7.5 dB over a wavelength range of 1610-1640 nm with -4V(pp) bias. The estimated Δα/α value is in the range of 2-3.3. The 3 dB bandwidth measurements show that the device is capable of operating at more than 30 GHz. Clear eye-diagram openings at 12.5 Gbps demonstrates large signal modulation at high transmission rate.

36 GHz submicron silicon waveguide germanium photodetector

Abstract: We present two effective approaches to improve the responsivity of high speed waveguide-based Ge photodetectors integrated on a 0.25μm silicon-on-insulator (SOI) platform. The main cause of poor responsivity is identified as metal absorption from the top contact to Ge. By optimizing Ge thickness and offsetting the contact window, we have demonstrated that the responsivity can be improved from 0.6A/W to 0.95A/W at 1550nm with 36GHz 3dB bandwidth. We also demonstrate that a wider device with double offset contacts can achieve 1.05A/W responsivity at 1550nm and 20GHz 3dB bandwidth.

Fabrication Insensitive Echelle Grating in Silicon-on-Insulator Platform

Abstract: We demonstrate a compact, low crosstalk, low loss, and flat passband demultiplexer based on an echelle grating fabricated in the silicon-on-insulator (SOI) platform. The demonstrated 12 channel demultiplexer has an 8-nm channel spacing, 5.5-nm flat passband, 1.7-dB on-chip loss, and better than 25-dB optical crosstalk. By arranging the output waveguides very close to the zero degree angle of the echelle grating, the performance of the demonstrated device is made insensitive to the vertical angle of the grating facet. The fabricated devices have a very small footprint and have the potential to provide a low-cost demultiplexer solution for multichannel data transmission applications.

Compact single-chip VMUX/DEMUX on the silicon-on-insulator platform

Abstract: We demonstrate a compact, single-chip 40-channel, dense wavelength division multiplexing (DWDM) variable attenuator multi/demultiplexer (VMUX/DEMUX) by monolithic integration of an echelle grating and high-speed p-i-n VOA on the silicon-on-insulator (SOI) platform. The demonstrated device has a flat-top filter shape, on chip loss of 5.0dB, low PDL of 0.3dB after compensation of the polarization dependent frequency (PDF) shift, a fast attenuation response speed of 3MHz, and an area of only 25mm by 10mm.

Terabit/s single chip WDM receiver on the SOI platform

Abstract: We demonstrate a Terabit/s receiver by monolithic integration of a polarization independent DWDM echelle grating and high-speed Ge photodiodes on the SOI platform. The compact device has an overall fiber-accessed responsivity of 0.4 A/W.

Design and fabrication of 3μm silicon-on-insulator waveguide integrated Ge electro-absorption modulator.

Abstract: We present the design and fabrication of a waveguide-based Ge electro-absorption (EA) modulator integrated with a 3µm silicon-on-isolator (SOI) waveguide. The proposed Ge EA modulator employs a butt-coupled horizontally-oriented p-i-n structure. The optical design achieves a low-loss transition from Ge to Si waveguides. The interaction between the optical mode of the waveguide and the bias induced electric field in the p-i-n structure was maximized to achieve high modulation efficiency. By balancing the trade-offs between the extinction ratio and the insertion loss of the device, an optimal working regime was identified. The measurement results from a fabricated device were used to verify the design. Under a −4Vpp reverse bias, the device demonstrates a total insertion loss (including the transition loss) of 2.7-5.2dB and an extinction ratio of 4.9-8.2dB over the wavelength range of 1610-1640nm. Subtracting the contribution of the transition loss, the Δα/α value for the fabricated device was estimated to be between 2.2 and 3.2 with an electric field around 55kV/cm.

High-speed and broadband electro-optic silicon switch with submilliwatt switching power

Abstract: We present a 2×2 silicon electro-optic switch with a submilliwatt switching power (0.6 mW), a broad bandwidth (60 nm), and ultrafast speed (6 ns). Free-carrier injection Mach-Zehnder interferometers are employed.

Low-power photonic components for optical interconnects

Abstract: Silicon-based optical interconnects are expected to provide high bandwidth and low power consumption solutions for chip-level communication applications, due to their electronics integration capability, proven manufacturing record and attractive price volume curve. In order to compete with electrical interconnects, the energy requirement is projected to be sub-pJ per bit for an optical link in chip to chip communication. Such low energies pose significant challenges for the optical components used in these applications. In this paper, we review several low power photonic components developed at Kotura for DARPA's Ultraperformance Nanophotonic Intrachip Communications (UNIC) project. These components include high speed silicon microring modulators, wavelength (de)multiplexers using silicon cascaded microrings, low power electro-optic silicon switches, low loss silicon routing waveguides, and low capacitance germanium photodetectors. Our microring modulators demonstrate an energy consumption of ~ 10 fJ per bit with a drive voltage of 1 V. Silicon routing waveguides have a propagation loss of < 0.3 dB/cm, enabling a propagation length of a few tens of centimeters. The germanium photodetectors can have a low device capacitance of a few fF, a high responsivity up to 1.1 A/W and a high speed of >30 GHz. These components are potentially sufficient to construct a full optical link with an energy consumption of less than 1 pJ per bit.

Integration of high speed Ge PIN photodetectors with WDM filter on SOI platform

Abstract: We demonstrate the integration of low dark current Ge photodetectors with a high performance demultiplexer on a large cross-section SOI waveguide platform. This Si-based WDM receiver can be used for multichannel terabit data transmission.

Monolithically integrated compact VMUX/DEMUX on silicon-on-insulator platform

Abstract: We demonstrate a compact 40-channel, dense wavelength division multiplexing (DWDM) VMUX/DEMUX by monolithic integration of an echelle grating and high-speed p-i-n VOA on the siliconon-insulator (SOI) platform. The demonstrated device has low optical loss, low PDL, fast attenuation response speed and an area of only 25mm by 10mm.