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Particle accelerators are essential tools in science, hospitals and industry.sup.1-6. Yet their costs and large footprint, ranging in length from metres to several kilometres, limit their use. The recently demonstrated nanophotonics-based acceleration of charged particles can reduce the cost and size of these accelerators by orders of magnitude.sup.7-9. In this approach, a carefully designed nanostructure transfers energy from laser light to the particles in a phase-synchronous manner, accelerating them. To accelerate particles to the megaelectronvolt range and beyond, with minimal particle loss.sup.10,11, the particle beam needs to be confined over extended distances, but the necessary control of the electron beam's phase space has been elusive. Here we demonstrate complex electron phase-space control at optical frequencies in the 225-nanometre narrow channel of a silicon-based photonic nanostructure that is 77.7 micrometres long. In particular, we experimentally show alternating phase focusing.sup.10-13, a particle propagation scheme for minimal-loss transport that could, in principle, be arbitrarily long. We expect this work to enable megaelectronvolt electron-beam generation on a photonic chip, with potential for applications in radiotherapy and compact light sources.sup.9, and other forms of electron phase-space control resulting in narrow energy or zeptosecond-bunched beams.sup.14-16. In a tiny chip-based particle accelerator, phase-space control of the emerging electron beam demonstrates guiding over a length of nearly 80 micrometres and an indispensable prerequisite to electron acceleration to high energies., Author(s): R. Shiloh [sup.1] , J. Illmer [sup.1] , T. Chlouba [sup.1] , P. Yousefi [sup.1] , N. Schönenberger [sup.1] [sup.2] , U. Niedermayer [sup.3] , A. Mittelbach [sup.1] , [...]

Accurate three-dimensional (3D) imaging is essential for machines to map and interact with the physical world.sup.1,2. Although numerous 3D imaging technologies exist, each addressing niche applications with varying degrees of success, none has achieved the breadth of applicability and impact that digital image sensors have in the two-dimensional imaging world.sup.3-10. A large-scale two-dimensional array of coherent detector pixels operating as a light detection and ranging system could serve as a universal 3D imaging platform. Such a system would offer high depth accuracy and immunity to interference from sunlight, as well as the ability to measure the velocity of moving objects directly.sup.11. Owing to difficulties in providing electrical and photonic connections to every pixel, previous systems have been restricted to fewer than 20 pixels.sup.12-15. Here we demonstrate the operation of a large-scale coherent detector array, consisting of 512 pixels, in a 3D imaging system. Leveraging recent advances in the monolithic integration of photonic and electronic circuits, a dense array of optical heterodyne detectors is combined with an integrated electronic readout architecture, enabling straightforward scaling to arbitrarily large arrays. Two-axis solid-state beam steering eliminates any trade-off between field of view and range. Operating at the quantum noise limit.sup.16,17, our system achieves an accuracy of 3.1 millimetres at a distance of 75 metres when using only 4 milliwatts of light, an order of magnitude more accurate than existing solid-state systems at such ranges. Future reductions of pixel size using state-of-the-art components could yield resolutions in excess of 20 megapixels for arrays the size of a consumer camera sensor. This result paves the way for the development and proliferation of low-cost, compact and high-performance 3D imaging cameras that could be used in applications from robotics and autonomous navigation to augmented reality and healthcare. A compact, high-performance silicon photonics-based light detection and ranging system for three-dimensional imaging is developed that should be amenable to low-cost mass manufacturing, Author(s): Christopher Rogers [sup.1] , Alexander Y. Piggott [sup.1] , David J. Thomson [sup.2] , Robert F. Wiser [sup.1] , Ion E. Opris [sup.3] , Steven A. Fortune [sup.1] , [...]

[Over time] Man's communications technologies... have moved from the verbal, to the alphabetic, to the typographic, to the filmic, and to the electronic..., [I]t would be absurd to presume that [...]

We introduce here multiplex nonlinear optical imaging as a powerful tool for studying the molecular organization and its transformation in cellular processes, with the specific example of apoptosis. Apoptosis is a process of self-initiated cell death, critically important for physiological regulation and elimination of genetic disorders. Nonlinear optical microscopy, combining the coherent anti-Stokes Raman scattering (CARS) microscopy and two-photon excited fluorescence (TPEF), has been used for analysis of spatial distribution of major types of biomolecules: proteins, lipids, and nucleic acids in the cells while monitoring their changes during apoptosis. CARS imaging revealed that in the nuclei of proliferating cells, the proteins are distributed nearly uniformly, with local accumulations in several nuclear structures. We have found that this distribution is abruptly disrupted at the onset of apoptosis and is transformed to a progressively irregular pattern. Fluorescence recovery after photobleaching (FRAP) studies indicate that pronounced aggregation of proteins in the nucleoplasm of apoptotic cells coincides with a gradual reduction in their mobility. biomolecular distribution | CARS imaging | cell doi/ 10.1073/pnas.1006374107

We present an extensive study of an ultracompact grating-based beam splitter suitable for photonic integrated circuits (PICs) that have stringent density requirements. The 10 [micro]m long beam splitter exhibits equal splitting, low insertion loss, and also provides a high extinction ratio in an integrated coherent balanced receiver. We further present the design strategies for avoiding mode distortion in the beam splitter and discuss optimization of the widths of the detectors to improve insertion loss and extinction ratio of the coherent receiver circuit. In our study, we show that the grating-based beam splitter is a competitive technology having low fabrication complexity for ultracompact PICs. OCIS codes: 230.1360, 130.3120.

We report the development of a sensor platform for detection of gelatinases based on porous silicon photonic films. The sensor is made by spin-coating gelatin, a substrate protein to gelatinases, onto the porous silicon, which forms a thin, uniform, and smooth gel layer where samples can be directly spotted. The digestion products of gelatin by the active gelatinase present in the sample are able to enter the pores and induce color changes that can be detected by the naked eye. Using this sensor, we have demonstrated the detection of matrix metalloproteinase-2 (MMP-2)--an important gelatinase closely associated with tumor aggressiveness and metastatic potential--with concentrations varying from 0.1 to 1000 ng/ mL in samples with volumes as small as 1 [micro]L. The detection limit of this method, in terms of the minimum quantity of active MMP-2 in the sample that can be detected, is 2 orders of magnitude lower than what has been reported for zymography.

A study was conducted to explore the properties of the defect mode of the omnidirectional gaps (ODGs) for the one-dimensional photonic crystal containing the indefinite metamaterial (IMMs) with a hyperbolic dispersion relation. Results revealed that spectral position of defect mode was observed to be weakly dependent on the incident angle of light and nearly invariant to the scale length of photonic crystal.

We investigate omnidirectional reflection from higher-order gaps in one-dimensional photonic crystals. Moreover, we present a designing criterion for omnidirectional reflection from several distinct gaps simultaneously, using only a single photonic crystal with a constant period. We show that for practical values of photonic crystals parameters, several relatively large omnidirectional gaps may be obtained. As an example, we demonstrate an omnidirectional reflector that exhibits two distinct wide omnidirectional ranges at near-infrared wavelengths. This omnidirectional reflector that operates in several ranges of wavelengths may have various potential applications. OCIS codes: 230.4170, 230.1480, 310.6860, 220.4830.

The general expression for a monochromatic antenna pattern is extended to a two dimensional function with dependence on both space and time. Expressions for the wideband antenna pattern in space and the impulse response in time are developed. The effects of random errors in the spatial domain and errors common to all elements with fluctuations in the frequency domain are analyzed. Examples are given, including RF beamformers and elements in finite arrays, but with an emphasis on a photonic beamformer, which shows improved performance relative to its RF counterparts in both the spatial and time domains. Index Terms--Antenna arrays, photonic beamforming, wideband beamforming networks, wideband phased array, wideband radar requirements.

Optics and photonics can be used to motivate students in physics courses at the high school, college, or university level. Many fundamental ideas and concepts can be taught by exploring wavelength division multiplexing as used in optical fiber communication systems. We describe a safe, simple, low-cost experimental apparatus that can be used to demonstrate the key concepts of wavelength division multiplexing. The apparatus can form the basis of several hands-on, active-learning activities. [DOI: 10.1119/1.2180284]

ABSTRACT The luminescence of trivalent lanthanide ions has found applications in lighting, lasers, optical telecommunications, medical diagnostics, and various other fields. This introductory review presents the basics of organic and [...]

We present a new technique-photon folding--for imaging in nonfocusing telescopes. Inspired by the epoch-folding method in timing analysis, the photon-folding technique directly provides the statistical significance of signals in images, by use of projection matrices. The technique is robust against common imaging problems such as aspect errors and a nonuniform background. The technique provides a deterministic recursive algorithm for improving images, which can be implemented on line. The higher-order photon-folding technique allows a systematic correction for coding noises, which is suitable for studying weak sources in the presence of highly variable strong sources. The technique can be applied to various types of nonfocusing telescopes such as coded-aperture optics, rotational collimators, or Fourier grid telescopes. OCIS codes: 110.7440, 340.7430.

A photonic encoder-decoder pair for optical code-division multiplexing (OCDM) that uses time-to-space converters and angle-multiplexed holograms is proposed. The encoder converts the pulse from each input port into a specific code and multiplexes input signals into the output port. The hologram in the decoder generates a correlation waveform between the transmitted code and the recorded code. The performance of the OCDM system with the encoder-decoder pair is estimated. The maximum spectral efficiency for 8-bit length orthogonal codes in the worst case at a bit-error rate of [10.sup.-9] is 0.17 (bits/s)/Hz when the number of channels is 8. OCIS codes: 060.0060, 060.4230, 070.6020, 090.4220, 200.4560.

Large telecommunications switching and transmission systems are gradually replacing some electric interconnection with optical interconnection. Parallel interconnection will be important for many system needs due to the need to produce larger switch fabrics. Subsystems will need to be interconnected with large bandwidth over major distances.The replacement of discrete optoelectronic and passive optics devices of an optical interconnection system, with parallel optical components, is described.

A new active photonic signal processor which achieves a high-Q microwave bandpass response if presented. It comprises active fiber within a pair of fiber Bragg gratings, and produces multiple taps with precise delay-time characteristics. The impulse response has demonstrated well in excess of 270 taps. The filter response demonstrates high resolution, having a narrow-band response with a Q of 325. The processor is also tunable, in both passband width and frequency. Index Terms - Fiber Bragg gratings, microwave photonics, photonic signal processing, optical delay-line filters.

An optoelectronic oscillator (OEO), capable of converting continuous-light energy into radio-frequency (RF) and microwave signals, generates phase-locked loops for photonic RF systems. The OEO consists of pump laser, feedback circuit, delay line, photodetector, an amplifier and a filter. The oscillator produces unstable spectrally pure microwave-reference signals up to 75 GHz with a phase noise below -140 dBc Hz at 10 KHz. The OEO gives both electrical and optical outputs. It can be synchronized to a reference point by optical and electrical injection locking, and can be self-phase locked.