On-chip Optical Communications Research Articles

A graphene-based broadband optical modulator

Integrated optical modulators with high modulation speed, small footprint and large optical bandwidth are poised to be the enabling devices for on-chip optical interconnects. Semiconductor modulators have therefore been heavily researched over the past few years. However, the device footprint of silicon-based modulators is of the order of millimetres, owing to its weak electro-optical properties. Germanium and compound semiconductors, on the other hand, face the major challenge of integration with existing silicon electronics and photonics platforms. Integrating silicon modulators with high-quality-factor optical resonators increases the modulation strength, but these devices suffer from intrinsic narrow bandwidth and require sophisticated optical design; they also have stringent fabrication requirements and limited temperature tolerances. Finding a complementary metal-oxide-semiconductor (CMOS)-compatible material with adequate modulation speed and strength has therefore become a task of not only scientific interest, but also industrial importance. Here we experimentally demonstrate a broadband, high-speed, waveguide-integrated electroabsorption modulator based on monolayer graphene. By electrically tuning the Fermi level of the graphene sheet, we demonstrate modulation of the guided light at frequencies over 1 GHz, together with a broad operation spectrum that ranges from 1.35 to 1.6 µm under ambient conditions. The high modulation efficiency of graphene results in an active device area of merely 25 µm(2), which is among the smallest to date. This graphene-based optical modulation mechanism, with combined advantages of compact footprint, low operation voltage and ultrafast modulation speed across a broad range of wavelengths, can enable novel architectures for on-chip optical communications.

Subwavelength metal-optic semiconductor nanopatch lasers

We report on near infrared semiconductor nanopatch lasers with subwavelength-scale physical dimensions (0.019 cubic wavelengths) and effective mode volumes (0.0017 cubic wavelengths). We observe lasing in the two most fundamental optical modes which resemble oscillating electrical and magnetic dipoles. The ultra-small laser volume is achieved with the presence of nanoscale metal patches which suppress electromagnetic radiation into free-space and convert a leaky cavity into a highly-confined subwavelength optical resonator. Such ultra-small lasers with metallodielectric cavities will enable broad applications in data storage, biological sensing, and on-chip optical communication.

Monolithic GaAs/InGaP nanowire light emitting diodes on silicon

Vertical light emitting diodes (LEDs) based on GaAs/InGaP core/shell nanowires,epitaxially grown on GaP and Si substrates, have been fabricated. The devices can befabricated over large areas and can be precisely positioned on the substrates, by the use ofstandard lithography techniques, enabling applications such as on-chip opticalcommunication. LED functionality was established on both kinds of substrate, and thedevices were evaluated in terms of temperature-dependent photoluminescence andelectroluminescence.

Pump–Probe Measurements of CMOS Detector Rise Time in the Blue

This paper proposes the use of shorter wavelengths and monolithic integration for chip-to-chip and on-chip optical communication. The promise of monolithic detectors for high-speed interconnection is demonstrated through experimental measurements and matching simulations. Responsivities >0.06 A/W and transit-time-limited response can be expected in the blue from planar p-i-n silicon-on-insulator (SOI) detectors.

Epitaxial Si1-xGex Films and Superlattice Structures Grown by CVD for Infrared Photodetectors

AbstractIntegration of photodetectors with high responsitivity in the near infrared (1.3-1.55 μm) on standard Si electronic circuits is important for a variety of applications in the field of on-chip, local area and long haul optical communications. In this work we report on a detailed structural and optical characterization of epitaxial Si1-xGex films and Si1-xGex /Si multilayers grown by chemical vapor deposition on (100) Si wafers. Cross-sectional transmission electron microscopy analyses show that metastable strained Si1-xGex films of few nanometer with x>40% can be deposited at low growth temperature and pressure. Absorption measurements on these films demonstrate the extension of the photo-response to 1.55 μm. Using these films as active layers Schottky integrated photodetectors have been fabricated.

Active feedback lightwave receivers

This paper describes new p-i-n-FET lightwave receivers that achieve high sensitivity without signal integration, and dynamic ranges large enough that they cannot be saturated by present lightwave transmitters. IC versions can be realized inexpensively in standard fine-line NMOS, CMOS, or GaAs IC technologies, and thus are suitable for loop-plant, local-area-network, and data link applications, as well as long-haul transmission applications. These receivers also can readily be designed for bit-rates in excess of 1 Gbit/s for high-capacity systems. In addition, these receivers can be implemented on the same IC as other system functions, e.g., for single-chip lightwave regenerators and lightwave modems, and, eventually, for microprocessors with on-chip optical communications ports.