[Show abstract][Hide abstract] ABSTRACT: Following significant research and development work over the past few years, silicon photonics has become a promising candidate to provide low-power, low-cost, and high-speed photonic links for telecommunication, data communication, and interconnect applications. A high-speed optical modulator is one of the critical components for these links. In this paper, we report on our recent progress in the development of a GeSi electro-absorption (EA) modulator based on the Franz-Keldysh effect (FKE) integrated in a 3-μm silicon-on-insulator (SOI) platform. We first discuss the FKE in GeSi, and describe the EA modulator device design and fabrication. We then report on the performance of the fabricated device. Finally, we describe the monolithic integration of four modulators with a four channel wavelength division multiplexing (WDM) echelle grating to demonstrate a 112 Gbit/s (4 × 28 Gbit/s) WDM transmitter chip. This chip establishes silicon photonics as an enabling technology for low-power and low-cost data transmission applications.
IEEE Journal of Selected Topics in Quantum Electronics 11/2013; 19(6):64-73. DOI:10.1109/JSTQE.2013.2278881 · 2.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have investigated the selective epitaxial growth of GeSi bulk material on silicon-on-insulator substrates by reduced pressure chemical vapor deposition. We employed AFM, SIMS, and Hall measurements, to characterize the GeSi heteroepitaxy quality. Optimal growth conditions have been identified to achieve low defect density, low RMS roughness with high selectivity and precise control of silicon content. Fabricated vertical p-i-n diodes exhibit very low dark current density of 5 mA/cm(2) at -1 V bias. Under a 7.5 V/mu m E-field, GeSi alloys with 0.6% Si content demonstrate very strong electro-absorption with an estimated effective Delta alpha/alpha around 3.5 at 1,590 nm. We compared measured Delta alpha/alpha performance to that of bulk Ge. Optical modulation up to 40 GHz is observed in waveguide devices while small signal analysis indicates bandwidth is limited by device parasitics.
[Show abstract][Hide abstract] ABSTRACT: We report the design and characterization of external-cavity DBR lasers built with a III-V-semiconductor reflective-SOA with spot-size converter edge-coupled to SOI waveguides containing Bragg grating mirrors. The un-cooled lasers have wall-plug-efficiencies of up to 9.5% at powers of 6 mW. The lasers are suitable for making power efficient, hybrid WDM transmitters in a CMOS-compatible SOI optical platform.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate a high speed GeSi electro-absorption (EA) modulator monolithically integrated on 3 µm silicon-on-insulator (SOI) waveguide. The demonstrated device has a compact active region of 1.0 × 55 μm<sup>2</sup>, an insertion loss of 5 dB and an extinction ratio of 6 dB at wavelength of 1550 nm. The modulator has a broad operating wavelength range of 35 nm and a 3 dB bandwidth of 40.7 GHz at 2.8 V reverse bias. This compact and energy efficient modulator is a key building block for optical interconnection applications.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate a high speed GeSi EA modulator with a broad operating wavelength range of over 30 nm near 1550 nm and a 3 dB bandwidth of 40.7 GHz at 2.8 V reverse bias.
Group IV Photonics (GFP), 2012 IEEE 9th International Conference on; 08/2012
[Show abstract][Hide abstract] ABSTRACT: We report a novel, compact design of high speed Ge photo detector
integrated with an echelle demultiplexer on a large cross-section SOI
platform with low insertion loss and low fiber coupling loss. A narrow
Ge photo detector waveguide is directly butt-coupled to a Si waveguide
to ensure low loss and high speed operation. With a Ge detector size of
only 0.8×15 μm2, the device achieves greater than 30
GHz modulation speed. The results indicate that the device speed is
transit time limited and that the detector performance benefits from the
high electron and hole drift velocity of germanium. The dark current of
the detector is less than 0.5μA at -1V. This small footprint high
speed Si-based WDM receiver can be fabricated using CMOS processes and
used for multichannel terabit data transmission with low manufacturing
Proceedings of SPIE - The International Society for Optical Engineering 05/2012; 8376:17-. DOI:10.1117/12.920831 · 0.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report a 9.5% wall-plug-efficient un-cooled external-cavity DBR laser built with a III-V-semiconductor reflective-SOA edge-coupled to an SOI waveguide containing a Bragg grating mirror. The hybrid laser is suitable for power efficient, CMOS-compatible optical transmitters.
Group IV Photonics (GFP), 2012 IEEE 9th International Conference on; 01/2012
[Show abstract][Hide abstract] 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.
Group IV Photonics (GFP), 2011 8th IEEE International Conference on; 10/2011
[Show abstract][Hide abstract] ABSTRACT: The silicon photonic devices are making new inroads into the semiconductor industry. A 3D mode transformer minimizes the coupling loss between a glass fiber and a Si waveguide. The 3D taper is less than 2 mm long and terminates in a point about 1 °m wide. A great advantage of silicon photonics is its electronic properties, adding the potential of optoelectronic and electrooptic interactions of photons and electrons. It makes possible electrical excitation and manipulation of light and optical conversion to electrical signals and even light control of light. Electrical contacts to p- and n- regions form the terminals of a p-i-n diode, where the, i-part (intrinsic) is the waveguide region. The steady-state and dynamic performance of the electronic-controlled variable optical attenuator (VOA) depends on the free-carrier absorption of electrons and holes within the intersection of a silicon electronic diode and a silicon photonic waveguide.
[Show abstract][Hide abstract] ABSTRACT: We present two effective approaches to improve the responsivity of high speed waveguide-based Ge photodetectors integrated on a 0.25 μm 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 0.95 A/W at 1550 nm with 36 GHz 3 dB bandwidth. We also demonstrate that a wider device with double offset contacts can achieve 1.05 A/W responsivity at 1550 nm and 20 GHz 3 dB bandwidth.
[Show abstract][Hide abstract] ABSTRACT: We present the design and fabrication of a waveguide-based Ge electro-absorption (EA) modulator integrated with a 3 µm 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 2.7-5.2 dB and an extinction ratio of 4.9-8.2 dB over the wavelength range of 1610-1640 nm. 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 55 kV/cm.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate a compact 40-channel, DWDM 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 low optical loss, low PDL, and fast response
[Show abstract][Hide abstract] 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 5.0 dB, low PDL of 0.3 dB after compensation of the polarization dependent frequency (PDF) shift, a fast attenuation response speed of 3 MHz, and an area of only 25 mm by 10 mm.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate a compact, low crosstalk, low loss, and flat passband demultiplexer based on an echelle grating fabri-cated 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. Index Terms—Diffraction gratings, photonic integrated cir-cuit, silicon-on-insulator (SOI), wavelength-division multiplexing (WDM).
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] ABSTRACT: As an enabling building block to support high bandwidth optical interconnections among supercomputing processing elements, we present the first monolithically integrated chipto-chip wavelength-division multiplexing (WDM) optical proximity coupler with 4-channel × 200GHz-spacing multiplexer/demultiplexer (MUX/DEMUX) functionality utilizing an echelle grating, micro reflective mirrors, and waveguide mode transformers on single silicon-on-insulator (SOI) substrate. This new photonic integrated circuits can be utilized to provide a data-rate independent optical interface that surpasses the throughput bottleneck of current electrical data paths.
Proceedings - Electronic Components and Technology Conference 01/2011; DOI:10.1109/ECTC.2011.5898604
[Show abstract][Hide abstract] ABSTRACT: This paper describes the development of a transmitter and receiver leveraging a combination of monolithic and hybrid integration for Datacenter applications to deliver 500Gbps over 2 km on a single mode fiber. The transmitter encompasses 12 electro-absorptive modulated lasers (EMLs) with wavelength channels from 1270 nm to 1380 nm on a 10 nm channel grid. The lasers are grouped in three (3) arrays with each array monolithically integrating four (4) EMLs operating at 43 Gbps each. The three EML arrays are flip-chip bonded to a planar light-guide circuit (PLC), which serves as the mounting platform and provides the optical multiplexer function. The receiver couples the signal through an optical PLC-based de-multiplexer to twelve (12) high-speed PIN detectors with a 3 dB bandwidth of more than 50 GHz. The transmission tests were performed over 2 km of SMF with each channel tested at 40 Gbps. For the demonstration, a commercial semiconductor optical amplifier was used in front of the receiver to boost the signal. Each channel was tested to be error free to <;10<sup>-11</sup> BER with most <;10<sup>-12</sup> BER. The total cross-talk was measured to be between 1 and 2dB. The channel spacing of 10nm was chosen to enable a low cost transmitter operation without using Thermo-Electric-Coolers (TEC) in order to reduce the overall power dissipation. Instead of a TEC, resistive heating can be used to limit the temperature excursions and to enable an operating range of the TOSA from -5 to +75 deg C. This technology demonstration is a step towards the final goal of 1 Terabit/s transmission for Datacenter applications.
MILITARY COMMUNICATIONS CONFERENCE, 2010 - MILCOM 2010; 12/2010
[Show abstract][Hide abstract] ABSTRACT: We report compact and low-loss silicon photonic filter devices that are readily integrated with actives to enable high-aggregate bitrate WDM systems. Data is presented for a 100Gbps link over 10km.
Optical Communication (ECOC), 2010 36th European Conference and Exhibition on; 10/2010
[Show abstract][Hide abstract] ABSTRACT: We present low loss shallow-ridge silicon waveguides with an average propagation loss of 0.274 dB/cm in the C-band, which can find applications in chip-level optical interconnects.
Photonics Society Summer Topical Meeting Series, 2010 IEEE; 08/2010