An all-solid-state, WDM silicon photonic digital link for chip-to-chip communications.

We describe a multiwavelength hybrid-integrated solid-state link on a 3 µm silicon-on-insulator (SOI) nanophotonic platform. The link spans three chips and employs germanium-silicon electroabsorption waveguide modulators, silicon transport waveguides, echelle gratings for multiplexing and demultiplexing, and pure germanium waveguide photo-detectors. The 8λ WDM Tx and Rx components are interconnected via a routing "bridge" chip using edge-coupled optical proximity communication.

High speed GeSi electro-absorption modulator at 1550 nm wavelength on SOI waveguide.

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(2), an insertion loss of 5 dB and an extinction ratio of 6 dB at wavelength of 1550 nm.

36 GHz submicron silicon waveguide germanium photodetector.

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.

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

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.

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

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.

Submilliwatt, ultrafast and broadband electro-optic silicon switches.

We present a broadband 2x2 electro-optic silicon switch with an ultralow switching power and fast switching time based on a Mach-Zehnder interferometer (MZI). Forward-biased p-i-n junctions are employed to tune the phase of silicon waveguides in the MZI, to achieve a π-phase switching power of 0.6 mW with a drive voltage 0.

1x4 reconfigurable demultiplexing filter based on free-standing silicon racetrack resonators.

We present a 1x4 reconfigurable demultiplexing filter based on cascaded thermally tunable silicon racetrack resonators with ultralow tuning powers. The use of free-standing silicon resonators with undercut structures significantly reduces the tuning power, with a figure of ~2.9 mW per free spectral range.

Thermally tunable silicon racetrack resonators with ultralow tuning power.

We present thermally tunable silicon racetrack resonators with an ultralow tuning power of 2.4 mW per free spectral range. The use of free-standing silicon racetrack resonators with undercut structures significantly enhances the tuning efficiency, with one order of magnitude improvement of that for previously demonstrated thermo-optic devices without undercuts.

High-speed and compact silicon modulator based on a racetrack resonator with a 1 V drive voltage.

Fast, compact, and power-efficient silicon microcavity electro-optic modulators are expected to be critical components for chip-level optical interconnects. It is highly desirable that these modulators can be driven by voltage swings of 1 V or less to reduce power dissipation and make them compatible with voltage supply levels associated with current and future complementary metal-oxide-semiconductor technology nodes. Here, we present a silicon racetrack resonator modulator that achieves over 8 dB modulation depth at 12.

Low loss shallow-ridge silicon waveguides.

We demonstrate low loss shallow-ridge silicon waveguides with an average propagation loss of 0.274 + or - 0.008 dB/cm in the C-band (1530 nm - 1565 nm).

Wavelength-tunable silicon microring modulator.

We present a wavelength-tunable, compact, high speed and low power silicon microring modulator. With a ring radius of 5 microm, we demonstrate a modulator with a high speed of 12.5 Gbps and a driving voltage of 3 V to achieve approximately 6 dB extinction ratio in high speed measurement.

Low power and compact reconfigurable multiplexing devices based on silicon microring resonators.

We present thermally reconfigurable multiplexing devices based on silicon microring resonators with low tuning power and low thermal crosstalk. Micro-heaters on top of the rings are employed to tune the resonant wavelengths through the thermo-optic effect of silicon. We achieve a low tuning power of 21 mW per free spectral range for a single ring by exploiting thermal isolation trenches close to the ring waveguides.

High speed carrier-depletion modulators with 1.4V-cm V(pi)L integrated on 0.25microm silicon-on-insulator waveguides.

We demonstrate a very efficient high speed silicon modulator with an ultralow pi-phase-shift voltage-length product V(pi)L = 1.4V-cm. The device is based on a Mach-Zehnder interferometer (MZI) fabricated using 0.

Vertical p-i-n germanium photodetector with high external responsivity integrated with large core Si waveguides.

We report a vertical p-i-n thin-film germanium photodetector integrated on 3microm thick large core silicon-on-insulator (SOI) waveguides. The device demonstrates very high external responsivity due to the low fiber coupling loss to the large core waveguides. The germanium width and thickness are carefully designed to achieve high responsivity yet retain high-speed performance.

Low Vpp, ultralow-energy, compact, high-speed silicon electro-optic modulator.

We present a high-speed silicon optical modulator with a low V(pp) (peak-to-peak driving voltage) and ultralow energy consumption based on a microring resonator, with the refractive index modulation achieved by electric-field-induced carrier depletion in a reverse-biased lateral pn diode embedded in the ring structure. With a V(pp) of 2 V, we demonstrate a silicon modulator with a 3 dB bandwidth of 11 GHz, a modulation depth of 6.5 dB together with an insertion loss of 2 dB, ultralow energy consumption of 50 fJ per bit, and a small device active area of approximately 1000 microm(2).

Diffuse optical tomographic reconstruction using multifrequency data.

We investigated the use of multifrequency diffuse optical tomography (MF-DOT) data for the reconstruction of the optical parameters. The experiments were performed in a 63 mm diameter cylindrical phantom containing a 15 mm diameter cylindrical object. Modulation frequencies ranging from 110 MHz to 280 MHz were used in the phantom experiments changing the contrast in absorption of the object with respect to the phantom while keeping the scattering value the same.

Combined diffuse optical tomography (DOT) and MRI system for cancer imaging in small animals.

Recently, there has been a great amount of interest in developing multi-modality imaging techniques for oncologic research and clinical studies with the aim of obtaining complementary information and, thus, improving the detection and characterization of tumors. In this present work, the details of a combined MR-diffuse optical imaging system for dual-modality imaging of small animals are given. As a part of this effort, a multi-spectral frequency domain diffuse optical tomography system is integrated with an MRI system.