All-Optical Modulation in a Silicon Waveguide Based on a Single-Photon Process

All-optical, low-power modulation is a major goal in photonics. Because of their high mode-field concentration and ease of manufacturing, nanoscale silicon waveguides offer an intriguing platform for photonics. So far, all-optical modulators built with silicon photonic circuits have relied on either two-photon absorption or the Kerr effect. Both effects are weak in silicon, and require extremely high (~5 W) peak optical power levels to achieve modulation. Here, we describe an all-optical Mach-Zehnder modulator based on a single-photon absorption (SPA) process, fabricated entirely in silicon. Our SPA modulator is based on a process by which a single photon at 1.55 mum is absorbed and an apparently free-carrier-mediated process causes an index shift in silicon, even though the photon energy does not exceed that of silicon's bandgap. We demonstrate all-optical modulation with a gate response of 1deg/mW at 0.5 Gb/s. This is over an order of magnitude more responsive than typical previously demonstrated devices. Even without resonant enhancement, further engineering may enable all optical modulation with less than 10 mW of gate power required for complete extinction, and speeds of 5 Gb/s or higher

Bankrollers: Lobbyists' Payments to the Lawmakers they Court, 1998-2006

Lobbyists and their political action committees (PACs) have contributed at least $103.1 million to members of Congress since 1998. This report is the first comprehensive effort to match names of lobbyists with Federal Election Commission campaign contribution data. The result provides details about the biggest lobbyist contributors and congressional recipients of campaign largesse and furnishes a contribution total nearly double the previous estimate.The report details the amounts given to members of Congress since 1998 by the 50 biggest lobbyist money-givers. Twenty-seven percent of lobbyists have contributed an amount to lawmakers large enough to be recognized by the Federal Election Commission ($200 or more), and a select 6.1 percent of lobbyists have contributed at least $10,000 -- totaling 83.4 percent of all lobbyist contributions. Many of the top recipients of congressional campaign money are on appropriations committees that dole out federal money.The report also records the rise of contributions by lobbyists from$17.8 million in the 2000 election cycle to $33.9 million in the 2004 cycle -- a 90.3 percent increase. In the 2006 election, lobbyists and their PACs are already on track to give about 10 percent more than in the previous cycle, not accounting for the expected increase in contributions as Election Day draws nearer.Profiling the 10 lobbyists who have given the most to members of Congress since 1998, the report also provides behind-the-scenes glimpses of some of the most egregious policy-making fiascos in recent years. One prime example is Kenneth Kies, who served as the chief of staff of the Congressional Joint Committee on Taxation from 1995 to 1998 and who, along with his wife Kathleen, is the study's fifth-highest lobbyist-contributor to Congress with$292,866 since 1998

High-Q optical resonators in silicon-on-insulator-based slot waveguides

This letter describes the design, fabrication and characterization of high-Q oval resonators based on slot waveguide geometries in thin silicon-on-insulator material. Optical quality factors of up to 27 000 were measured in such filters, and we estimate losses of –10 dB/cm in the slotted waveguides on the basis of our resonator measurements. Such waveguides enable the concentration of light to very high optical fields within nanoscale dimensions, and show promise for the confinement of light in low-index material with potential applications for optical modulation, nonlinear optics and optical sensing

Integrated plasmon and dielectric waveguides

We have designed, fabricated and characterized surface plasmon waveguides for near infrared light in the telecommunications spectrum. These waveguides exhibit losses of -1.2dB/μm and can guide light around 0.5 μm bends. Light can also be efficiently coupled between more conventional silicon waveguides and these plasmon waveguides with compact couplers, and we demonstrate that surface plasmon optical devices can be constructed by using planar circuit fabrication techniques. The large optical field enhancements of metallic surface plasmon devices are expected to lead to a new class of plasmonic optical devices, which will take advantage of the large field enhancements at the surfaces of the plasmon waveguides for nonlinear or sensing functionality, while utilizing the low losses available in silicon waveguides to move light longer distances on chip

High-Q ring resonators in thin silicon-on-insulator

We have fabricated high-Q microrings from thin silicon-on-insulater SOI layers and measured Q values of 45 000 in these rings, which were then improved to 57 000 by adding a PMMA cladding. The optimal waveguide designs were calculated, and the waveguide losses were analyzed. These high-Q resonators are expected to lead to interesting devices for telecommunication filters and sources as well as optical refractive index sensing

Modal reflectivity in finite-depth two-dimensional photonic-crystal microcavities

We present finite-difference time-domain calculations of the Q factor for an optical microcavity defined by a slab waveguide and two-dimensional photonic-crystal end mirrors. The effect of the finite depth of the photonic crystal on the cavity s optical modes is examined. From these calculations, we can optimize the performance of the photonic-crystal mirrors and determine the loss mechanisms within optical cavities defined by these structures. The Q of the cavity modes is shown to be strongly dependent on the depth of the holes defining the photonic crystal, as well as the refractive index of the material surrounding the waveguide core

On the p-norm condition number of the multivariate triangular Bernstein basis

AbstractWe show that the p-norm condition number of the s-variate triangular Bernstein basis for polynomials of degree n grows at most as O(ns2n) for fixed s and increasing n. This is essentially the same growth as has already been established in the univariate case

Microscaled and nanoscaled platinum sensors

We show small and robust platinum resistive heaters and thermometers that are defined by microlithography on silicon substrates. These devices can be used for a wide range of applications, including thermal sensor arrays, programmable thermal sources, and even incandescent light emitters. To explore the miniaturization of such devices, we have developed microscaled and nanoscaled platinum resistor arrays with wire widths as small as 75 nm, fabricated lithographically to provide highly localized heating and accurate resistance (and hence temperature) measurements. We present some of these potential applications of microfabricated platinum resistors in sensing and spectroscopy