Olav Solgaard

Bio: Olav Solgaard is an academic researcher from Stanford University. The author has contributed to research in topics: Photonic crystal & Optical fiber. The author has an hindex of 55, co-authored 488 publications receiving 11778 citations. Previous affiliations of Olav Solgaard include University of California, Berkeley & Stony Brook University.

Method and apparatus for modulating a light beam

Abstract: A modulator for modulating an incident beam of light, the modulator comprising a plurality of equally spaced-apart elements, each of which includes a light-reflective planar surface. The elements are arranged parallel to each other with their light-reflective surfaces parallel to each other. The modulator includes means for supporting the elements in relation to one another and means for moving particular ones of the elements relative to others so that the moved elements transit between a first configuration wherein the modulator acts to reflect the incident beam of light as a plane mirror, and a second configuration wherein the modulator diffracts the light reflected therefrom. In operation the light-reflective surfaces of the elements remain parallel to each other in both the first and second configurations. The perpendicular spacing between the reflective surfaces of the respective elements is equal to m/4 × the wavelength of the incident beam of light, wherein m equals an even whole number or zero when the elements are in the first configuration and m equals an odd whole number when the elements are in the second configuration.

An atomic force microscope tip designed to measure time-varying nanomechanical forces.

Abstract: Tapping-mode atomic force microscopy (AFM), in which the vibrating tip periodically approaches, interacts and retracts from the sample surface, is the most common AFM imaging method. The tip experiences attractive and repulsive forces that depend on the chemical and mechanical properties of the sample, yet conventional AFM tips are limited in their ability to resolve these time-varying forces. We have created a specially designed cantilever tip that allows these interaction forces to be measured with good (sub-microsecond) temporal resolution and material properties to be determined and mapped in detail with nanoscale spatial resolution. Mechanical measurements based on these force waveforms are provided at a rate of 4 kHz. The forces and contact areas encountered in these measurements are orders of magnitude smaller than conventional indentation and AFM-based indentation techniques that typically provide data rates around 1 Hz. We use this tool to quantify and map nanomechanical changes in a binary polymer blend in the vicinity of its glass transition. Phase changes and chemical compositional variations in materials on the nanoscale have been studied using various scanning force microscopy techniques. In these techniques, a force-sensing cantilever with a sharp tip is placed in continuous contact with the sample surface. Dynamical properties of the cantilever are adjusted depending on the material in contact with the tip. Examples of these techniques include ultrasonic force microscopy 1 , force modulation microscopy 2 , shear modulation force microscopy and lateral force microscopy 3,4 .T hese

Multi-wavelength cross-connect optical switch

Abstract: A cross-connect switch for fiber-optic communication networks employing a wavelength dispersive element, such as a grating, and a stack of regular (non-wavelength selective) cross bar switches using two-dimensional arrays of micromachined, electrically actuated, individually-tiltable, controlled deflection micro-mirrors for providing multiport switching capability for a plurality of wavelengths. Using a one-dimensional micromirror array, a fiber-optic based MEMS switched spectrometer that does not require mechanical motion of bulk components or large diode arrays can be constructed with readout capability for WDM network diagnosis or for general purpose spectroscopic applications.

Optical MEMS for Lightwave Communication

Abstract: The intensive investment in optical microelectromechanical systems (MEMS) in the last decade has led to many successful components that satisfy the requirements of lightwave communication networks. In this paper, we review the current state of the art of MEMS devices and subsystems for lightwave communication applications. Depending on the design, these components can either be broadband (wavelength independent) or wavelength selective. Broadband devices include optical switches, crossconnects, optical attenuators, and data modulators, while wavelength-selective components encompass wavelength add/drop multiplexers, wavelength-selective switches and crossconnects, spectral equalizers, dispersion compensators, spectrometers, and tunable lasers. Integration of MEMS and planar lightwave circuits, microresonators, and photonic crystals could lead to further reduction in size and cost

Deformable grating optical modulator.

Abstract: A new type of light modulator, the deformable grating modulator, based on electrically controlling the amplitude of a micromachined phase grating is described. Mechanical motion of one quarter of a wavelength is sufficient for switching in this device. The small mechanical motion allows the use of structures with high mechanical resonance frequencies. We have developed a deformable grating modulator with a bandwidth of 1.8 MHz and a switching voltage of 3.2 V and have demonstrated modulation with 16 dB of contrast. Smaller devices with bandwidths of as much as 6.1 MHz and predicted switching voltages of less than 10 V were also fabricated.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Flat Optics With Designer Metasurfaces

Abstract: Metamaterials are artificially fabricated materials that allow for the control of light and acoustic waves in a manner that is not possible in nature. This Review covers the recent developments in the study of so-called metasurfaces, which offer the possibility of controlling light with ultrathin, planar optical components. Conventional optical components such as lenses, waveplates and holograms rely on light propagation over distances much larger than the wavelength to shape wavefronts. In this way substantial changes of the amplitude, phase or polarization of light waves are gradually accumulated along the optical path. This Review focuses on recent developments on flat, ultrathin optical components dubbed 'metasurfaces' that produce abrupt changes over the scale of the free-space wavelength in the phase, amplitude and/or polarization of a light beam. Metasurfaces are generally created by assembling arrays of miniature, anisotropic light scatterers (that is, resonators such as optical antennas). The spacing between antennas and their dimensions are much smaller than the wavelength. As a result the metasurfaces, on account of Huygens principle, are able to mould optical wavefronts into arbitrary shapes with subwavelength resolution by introducing spatial variations in the optical response of the light scatterers. Such gradient metasurfaces go beyond the well-established technology of frequency selective surfaces made of periodic structures and are extending to new spectral regions the functionalities of conventional microwave and millimetre-wave transmit-arrays and reflect-arrays. Metasurfaces can also be created by using ultrathin films of materials with large optical losses. By using the controllable abrupt phase shifts associated with reflection or transmission of light waves at the interface between lossy materials, such metasurfaces operate like optically thin cavities that strongly modify the light spectrum. Technology opportunities in various spectral regions and their potential advantages in replacing existing optical components are discussed.

Plasmonics beyond the diffraction limit

Abstract: Recent years have seen a rapid expansion of research into nanophotonics based on surface plasmon–polaritons. These electromagnetic waves propagate along metal–dielectric interfaces and can be guided by metallic nanostructures beyond the diffraction limit. This remarkable capability has unique prospects for the design of highly integrated photonic signal-processing systems, nanoresolution optical imaging techniques and sensors. This Review summarizes the basic principles and major achievements of plasmon guiding, and details the current state-of-the-art in subwavelength plasmonic waveguides, passive and active nanoplasmonic components for the generation, manipulation and detection of radiation, and configurations for the nanofocusing of light. Potential future developments and applications of nanophotonic devices and circuits are also discussed, such as in optical signals processing, nanoscale optical devices and near-field microscopy with nanoscale resolution.

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

Abstract: Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

Bound states in the continuum

Abstract: Bound states in the continuum (BICs) are waves that remain localized even though they coexist with a continuous spectrum of radiating waves that can carry energy away. Their very existence defies conventional wisdom. Although BICs were first proposed in quantum mechanics, they are a general wave phenomenon and have since been identified in electromagnetic waves, acoustic waves in air, water waves and elastic waves in solids. These states have been studied in a wide range of material systems, such as piezoelectric materials, dielectric photonic crystals, optical waveguides and fibres, quantum dots, graphene and topological insulators. In this Review, we describe recent developments in this field with an emphasis on the physical mechanisms that lead to BICs across seemingly very different materials and types of waves. We also discuss experimental realizations, existing applications and directions for future work. The fascinating wave phenomenon of ‘bound states in the continuum’ spans different material and wave systems, including electron, electromagnetic and mechanical waves. In this Review, we focus on the common physical mechanisms underlying these bound states, whilst also discussing recent experimental realizations, current applications and future opportunities for research.