Measurements of the contact potential difference between different materials have been performed for the first time using scanning force microscopy. The instrument has a high resolution for both the contact potential difference (better than 0.1 mV) and the lateral dimension (<50 nm) and allows the simultaneous imaging of topography and contact potential difference. Images of gold, platinum, and palladium surfaces, taken in air, show a large contrast in the contact potential difference and demonstrate the basic concept.

It is known that light can be slowed down in dispersive materials near resonances. Dramatic reduction of the light group velocity-and even bringing light pulses to a complete halt-has been demonstrated recently in various atomic and solid state systems, where the material absorption is cancelled via quantum optical coherent effects. Exploitation of slow light phenomena has potential for applications ranging from all-optical storage to all-optical switching. Existing schemes, however, are restricted to the narrow frequency range of the material resonance, which limits the operation frequency, maximum data rate and storage capacity. Moreover, the implementation of external lasers, low pressures and/or low temperatures prevents miniaturization and hinders practical applications. Here we experimentally demonstrate an over 300-fold reduction of the group velocity on a silicon chip via an ultra-compact photonic integrated circuit using low-loss silicon photonic crystal waveguides that can support an optical mode with a submicrometre cross-section. In addition, we show fast (approximately 100 ns) and efficient (2 mW electric power) active control of the group velocity by localized heating of the photonic crystal waveguide with an integrated micro-heater.

This paper describes the design and construction of the MicroBooNE liquid argon time projection chamber and associated systems. MicroBooNE is the first phase of the Short Baseline Neutrino program, located at Fermilab, and will utilize the capabilities of liquid argon detectors to examine a rich assortment of physics topics. In this document details of design specifications, assembly procedures, and acceptance tests are reported.

We demonstrate a new method whereby near-field optical microscope resolution can be extended to the nanometer regime. The technique is based on measuring the modulation of the scattered electric field from the end of a sharp silicon tip as it is stabilized and scanned in close proximity to a sample surface. Our initial results demonstrate resolution in the 3 nm range--comparable to what can be achieved with typical attractive mode atomic force microscopes. Theoretical considerations predict that the ultimate resolution achievable with this approach could be close to the atomic level.Following the demonstration of super-resolution by nearfield scarming microscopy at microwave frequencies' and its subsequent extension to the visible regionz9 the field of near-field scanning microscopy (NSOM) has attracted much attention. Particularly over the past few years, NSOM has enjoyed a rapid growth."15 This growth has been assisted by several important contributions to the technology such as the use of tapered single mode optical fibers," independently stabilizing the tip-sample spacing by shear-force contro17'8 and methods for measuring the polarization9 and fluorescence" of samples on the sub-50 nm scale. In this letter, we introduce a technique whereby the resolution of near-field optical microscopes can be extended below 1 nm, i.e., over an order of magnitude better than what has been achieved so far.The majority of near-field optical microscopes employ tapered single mode optical fibers coated on the sides with aluminum in order to form a subwavelength aperture at their ends. The aluminum (skin depth 12 nm at 633 nm wavelength) which is essential for the operation of most NSOMs serves to confine the light within the optical fiber as it enters the tip end thereby defining either a tiny light source (for illumination mode NSOM) or a tiny light collector (for collection mode NSOM). The smallest aperture that can be made in this way cannot be much smaller than twice the optical skin depth in aluminum, since the light has to be significantly attenuated as it leaks out of the fiber sides into the aluminum in order to define an aperture. Thus, spatial resolutions achieved in the NSOM are in the 30-50 nm range. This resolution although superior to the early images taken with NSOM are still an order of magnitude away from what can be achieved with typical attractive mode atomic force microscopes (AFMs>.~~ The concept we have explored is based on an idea that occurred to one of us several years ag0.t' Rather than transmitting light through a fine aperture, we use the spherical light scattering from a tip end of a standard Al?M or scanning tunnel microscopy @TM) to define the light source. Although in principle this concept allows one tomake scattering sources down to atomic dimensions (as in STM and AFM tips), it provides significant challenges for detecting the minute quantity of scattered light from the tip end in the presence of a large background. We have been able to overcome these difficulties. Here we present initial resu...

Phase-change storage is widely used in optical information technologies (DVD, CD-ROM and so on), and recently it has also been considered for non-volatile memory applications. This work reports advances in thermal data recording of phase-change materials. Specifically, we show erasable thermal phase-change recording at a storage density of 3.3 Tb inch(-2), which is three orders of magnitude denser than that currently achievable with commercial optical storage technologies. We demonstrate the concept of a thin-film nanoheater to realize ultra-small heat spots with dimensions of less than 50 nm. Finally, we show in a proof-of-concept demonstration that an individual thin-film heater can write, erase and read the phase of these storage materials at competitive speeds. This work provides important stepping stones for a very-high-density storage or memory technology based on phase-change materials.

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Coupled resonator optical waveguides (CROWs) comprised of up to 16 racetrack resonators based on silicon-on-insulator (SOI) photonic wires were fabricated and characterized. The optical properties of the CROWs were simulated using measured single resonator parameters based on a matrix approach. The group delay property of CROWs was also analyzed. The SOI based CROWs consisting of multiple resonators have extremely small footprints and can find applications in optical filtering, dispersion compensation, and optical buffering. Moreover, such CROW structure is a promising candidate for exploration of low light level nonlinear optics due to its resonant nature and compact mode size (∼0.1μm2) in photonic wire.

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