A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

We examine the current performance and future demands of interconnects to and on silicon chips. We compare electrical and optical interconnects and project the requirements for optoelectronic and optical devices if optics is to solve the major problems of interconnects for future high-performance silicon chips. Optics has potential benefits in interconnect density, energy, and timing. The necessity of low interconnect energy imposes low limits especially on the energy of the optical output devices, with a ~ 10 fJ/bit device energy target emerging. Some optical modulators and radical laser approaches may meet this requirement. Low (e.g., a few femtofarads or less) photodetector capacitance is important. Very compact wavelength splitters are essential for connecting the information to fibers. Dense waveguides are necessary on-chip or on boards for guided wave optical approaches, especially if very high clock rates or dense wavelength-division multiplexing (WDM) is to be avoided. Free-space optics potentially can handle the necessary bandwidths even without fast clocks or WDM. With such technology, however, optics may enable the continued scaling of interconnect capacity required by future chips.

Device Requirements for Optical Interconnects to Silicon Chips

Single-molecule surface-enhanced Raman scattering (SM-SERS) is one of the vital applications of plasmonic nanoparticles. The SM-SERS sensitivity critically depends on plasmonic hot-spots created at the vicinity of such nanoparticles. In conventional fluid-phase SM-SERS experiments, plasmonic hot-spots are facilitated by chemical aggregation of nanoparticles. Such aggregation is usually irreversible, and hence, nanoparticles cannot be re-dispersed in the fluid for further use. Here, we show how to combine SM-SERS with plasmon polariton-assisted, reversible assembly of plasmonic nanoparticles at an unstructured metal–fluid interface. One of the unique features of our method is that we use a single evanescent-wave optical excitation for nanoparticle assembly, manipulation and SM-SERS measurements. Furthermore, by utilizing dual excitation of plasmons at metal–fluid interface, we create interacting assemblies of metal nanoparticles, which may be further harnessed in dynamic lithography of dispersed nanostructures. Our work will have implications in realizing optically addressable, plasmofluidic, single-molecule detection platforms. Plasmonic hot-spot generation in solution is not reversible for single-molecule surface-enhanced Raman scattering, which limits its applications. Patra et al.tackle this problem by integrating this technique with thermo-plasmon-assisted reconfiguration of nanoparticles at a metal–fluid interface.

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Plasmofluidic single-molecule surface-enhanced Raman scattering from dynamic assembly of plasmonic nanoparticles

The fact that light carries both linear and angular momentum is well-known to physicists. One application of the linear momentum of light is for optical tweezers, in which the refraction of a laser beam through a particle provides a reaction force that draws the particle towards the centre of the beam. The angular momentum of light can also be transfered to particles, causing them to spin. In fact, the angular momentum of light has two components that act through different mechanisms on various types of particle. This Review covers the creation of such beams and how their unusual intensity, polarization and phase structure has been put to use in the field of optical manipulation.

Tweezers with a twist

The silicon chip has been the mainstay of the electronics industry for the last 40 years and has revolutionized the way the world operates. Today, a silicon chip the size of a fingernail contains nearly 1 billion transistors and has the computing power that only a decade ago would take up an entire room of servers. As the relentless pursuit of Moore's law continues, and Internet-based communication continues to grow, the bandwidth demands needed to feed these devices will continue to increase and push the limits of copper-based signaling technologies. These signaling limitations will necessitate optical-based solutions. However, any optical solution must be based on low-cost technologies if it is to be applied to the mass market. Silicon photonics, mainly based on SOI technology, has recently attracted a great deal of attention. Recent advances and breakthroughs in silicon photonic device performance have shown that silicon can be considered a material onto which one can build optical devices. While significant efforts are needed to improve device performance and commercialize these technologies, progress is moving at a rapid rate. More research in the area of integration, both photonic and electronic, is needed. The future is looking bright. Silicon photonics could provide low-cost opto-electronic solutions for applications ranging from telecommunications down to chip-to-chip interconnects, as well as emerging areas such as optical sensing technology and biomedical applications. The ability to utilize existing CMOS infrastructure and manufacture these silicon photonic devices in the same facilities that today produce electronics could enable low-cost optical devices, and in the future, revolutionize optical communications

http://ieeexplore.ieee.org/iel5/6668/34347/01638290.pdf

Silicon photonics

Summary form only given. In this paper, we report a systematic study of spectral effects at various wavelengths relative to the zero group velocity dispersion (GVD) point in the fibre. The fibres used in our experiments had core diameters of 1.6 /spl mu/m and 2.5 /spl mu/m corresponding to a zero GVD point at 680 nm and 790 nm, respectively. Light from a 10 fs Ti:sapphire laser, centred on 800 nm, was coupled into both of these fibres and the smaller core fibre produced a spectrum corresponding to a four-wave mixing peak in the visible portion of the spectrum and a soliton self-frequency-shifted spectral feature in the near infra-red. The larger core fibre produced an almost continuous spectrum.

Wavelength dependence of induced nonlinear effects in photonic crystal fibre

Wavelet transformations retain all of the pertinent Fourier transformation properties of ultrashort pulses while representing the time-frequency domain. Use of a particular transformation in an interferrometric device is demonstrated.

Wavelet transformations for ultrashort pulse characterization

We developed a SERS biosensor based on gold fishnets fabricated by using e-beam lithography. This device is used for glycerophosphoinositol (GroPIns) molecule sensing. GroPIns is an abundant component of cell cytosol and high GroPIns levels have been reported in several tumour cells. We demonstrate that our SERS sensor is able to accurately and quantitatively determine the concentration of GroPIns. These results indicate that SERS may provide a novel platform technology to identify GroPIns profiles in disease pathogenesis.

Biomolecular sensing for cancer diagnostics using highly reproducible SERS substrates

We discuss here the performance of a new method for determining both the azimuthal as well as radial indices of a Laguerre-Gaussian beam by measuring the far-field diffraction pattern from a tailored annular triangular aperture.

Characterizing the azimuthal and radial mode indices of a laguerre-gaussian beam using diffraction from a triangular aperture

Fluorescence suppression using modulated wavelength Raman spectroscopy has been investigated using a fiber Raman probe and micro-Raman spectroscopy. This may lead to enhanced differentiation between normal and cancerous tissues and cells.

Michael Mazilu

Papers

Wavelength dependence of induced nonlinear effects in photonic crystal fibre

Wavelet transformations for ultrashort pulse characterization

Biomolecular sensing for cancer diagnostics using highly reproducible SERS substrates

Characterizing the azimuthal and radial mode indices of a laguerre-gaussian beam using diffraction from a triangular aperture

Fluorescence Suppression Using Modulated Wavelength Raman Spectroscopy for Tissue and Cell Analysis